Title 24 · California Energy Code
What is an energy budget — Long‑Term System Cost (LSC) vs Source Energy
The California Energy Code requires new buildings to meet two energy budgets — **LSC** (an hourly cost‑weighted metric) and **Source Energy** (total annual source Btu) — calculated with CEC‑published factors and Commission‑certified software; additions/alterations are judged using **LSC** only.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
An energy budget is the maximum energy a proposed building may be designed to consume; for newly constructed buildings it is expressed in both Long‑Term System Cost (LSC) and Source Energy, while for additions/alterations it is expressed in LSC only. The performance compliance path requires the proposed design’s calculated LSC and Source Energy not to exceed the standard‑design energy budgets using Commission‑certified compliance software. See § 100.2, § 140.1, § 150.1, and § 170.1 for the controlling rules.
The single most important rule: the building must be modeled with Commission‑certified software and its LSC and Source Energy consumptions must be no greater than the standard‑design energy budgets (new buildings use both LSC and Source Energy; additions/alterations use LSC).
Requirements in detail
Key definitions (first mention bolded)
- Energy budget — the maximum energy consumption a proposed building may be designed to consume. § 100.2 and definitions.
- Long‑Term System Cost (LSC) — an hourly, cost‑weighted metric computed by multiplying site energy use each hour by CEC‑published LSC hourly factors (vary by hour, energy type, climate zone, and building type). § 100.2.
- Source Energy — the total annual source energy calculated by multiplying hourly site energy use by Btu/source‑energy factors that reflect fossil fuels consumed on‑site or caused to be consumed to meet electrical demand using Commission‑projected long‑term marginal hourly resources. § 100.2.
- Efficiency LSC — the sum of the LSC energy for space‑conditioning, water heating, mechanical ventilation and lighting (and sometimes self‑utilization credit). § 140.1 / § 150.1 / § 170.1.
- Total LSC — Efficiency LSC plus LSC credit/energy from photovoltaics (PV), battery energy storage systems (BESS), demand flexibility, and where applicable other loads. § 140.1 / § 150.1 / § 170.1.
Who uses which metric (short summary)
- Newly constructed single‑family, multifamily, and nonresidential buildings: both LSC and Source Energy. § 100.2, § 140.1, § 150.1, § 170.1.
- Additions and alterations: LSC only. § 100.2.
How each budget is calculated (high level)
- LSC: Hourly site energy (kWh, therms, gallons) × CEC‑published LSC hourly factors (different by hour, energy type, climate zone, and building type; summarized in Reference Joint Appendix JA3). § 100.2.
- Source Energy: Hourly site energy × Btu factors that account for fuel consumed on‑site or caused by the building’s electrical demand using Commission‑projected long‑term marginal hourly generation. § 100.2.
Decision‑relevant dimensions / quick reference table
| Decision dimension / value | Practical effect | Code reference |
|---|---|---|
| Which budgets apply to new construction | Both LSC and Source Energy must be modeled and met | § 100.2, § 140.1, § 150.1, § 170.1 |
| Which budgets apply to additions/alterations | LSC only | § 100.2 |
| LSC components | Efficiency LSC (HVAC, water heat, ventilation, lighting, self‑utilization) and Total LSC (adds PV, BESS, demand flexibility) | § 140.1, § 150.1, § 170.1 |
| How LSC values are obtained | Hourly multiplication of site energy by LSC hourly factors published by the CEC (see JA3) | § 100.2; Reference JA3 |
| How Source Energy values are obtained | Hourly multiplication of site energy by Btu/source energy factors that include long‑term marginal generation mix | § 100.2 |
| Software requirement | Use Commission‑certified compliance software (Sections 10‑109 / 10‑116 referenced) to calculate energy budgets and compliance | § 140.1, § 150.1, § 170.1 |
| Community‑shared PV/BESS | May offset part/all of required PV/BESS LSC energy if approved per Title 24 Part 1, § 10‑115 (see exceptions in performance sections) | Exceptions in § 140.1, § 150.1, § 170.1; see § 10‑115 reference |
Exceptions & special cases
- Community‑shared solar or shared BESS: Where a community shared system provides dedicated power or utility credits/payments and is approved by the Energy Commission under § 10‑115, it may offset part or all of the PV/BESS LSC energy required to comply. Exceptions appear in § 140.1, § 150.1, and § 170.1.
- Source Energy exception in § 170.1: For the nonresidential performance approach, source energy budget determination applies the standard design requirements except with a consumer gas or propane water heater (i.e., the source budget is determined excluding that consumer gas/propane water heater in the standard design). See § 170.1(a)2.
- Additions and alterations: Always expressed and judged using LSC; Source Energy is not used for additions/alterations per § 100.2.
Common mistakes
- Treating site energy numbers (kWh, therms) as the budget metric instead of computing LSC and Source Energy per the code (LSC uses hourly LSC factors; source energy uses Btu factors). The code explicitly requires these conversions. § 100.2.
- Forgetting to model both LSC and Source Energy for new construction (both are required); only additions/alterations use LSC only. § 100.2, § 140.1, § 150.1, § 170.1.
- Omitting PV/BESS/demand flexibility contributions from Total LSC calculations (these items are part of the Total LSC when present). § 140.1, § 150.1, § 170.1.
- Using non‑certified software or manual shortcuts instead of Commission‑certified compliance software required by Sections 10‑109 and 10‑116 for the performance method. The performance sections point to those certification requirements.
- Misapplying community‑shared offsets without Energy Commission approval per § 10‑115; the code requires Commission‑established methods and approvals. § 140.1 / § 150.1 / § 170.1 exceptions.
Worked example — illustrative (numbers are hypothetical; use Commission factors for official work)
The code prescribes an hourly method; the official hourly LSC hourly factors and Btu/source energy factors are published by the CEC (Reference JA3 and related tables). The following is an illustrative calculation to show method and units — do NOT use these example factors for permit compliance.
Scenario (annual totals, simplified for illustration):
- Annual electricity use (site): 5,000 kWh
- Annual natural gas use (site): 400 therms
LSC method (conceptual steps from § 100.2):
- For each hour of the year, obtain the site electricity and gas used during that hour (kWh, therms).
- Multiply each hourly site quantity by the CEC LSC hourly factor for that energy type/hour/climate zone. Sum all hourly LSC contributions for electricity and gas over 8,760 hours to get the building’s LSC (Efficiency LSC components broken out by end‑use if needed). § 100.2, § 140.1.
Illustrative arithmetic (hypothetical average factors — NOT code values):
- Assume an illustrative average LSC factor for electricity = $0.10 per kWh equivalent LSC unit and for gas = $0.50 per therm equivalent LSC unit (these are made‑up numbers for method only).
- Efficiency LSC (illustrative) = 5,000 kWh × 0.10 + 400 therms × 0.50 = $500 + $200 = $700 Efficiency LSC.
- If the project has PV and BESS that reduce LSC by a hypothetical $250, Total LSC = $700 − $250 = $450. (In actual code LSC units are LSC energy units produced by hourly factors — values and sign conventions are from CEC tables and software.) § 140.1 / § 150.1 / § 170.1.
Source Energy method (conceptual steps from § 100.2):
- Multiply hourly site electricity and gas by the applicable Btu/source energy factors (which include long‑term marginal generation mix for electricity). Sum hourly contributions to get total annual Source Energy.
Important note: the actual compliance process uses Commission‑certified software that contains the correct hourly LSC factors and source energy Btu factors (Reference JA3 and the ACM/ACM Reference Manuals); do not substitute the illustrative numeric factors above for official compliance. § 100.2 and performance sections require use of the certified software.
Related provisions
- § 100.2 — Calculation of energy budgets; LSC hourly factor method and source energy Btu factors referenced.
- § 140.1 — Energy budgets for nonresidential performance approach; LSC and Source Energy definitions/components.
- § 150.1 — Performance approach for single‑family residential buildings; LSC and Source Energy definitions/components.
- § 170.1 — Performance approach for multifamily/nonresidential (performance compliance); LSC and Source Energy definitions/components and the consumer gas/propane water heater exception.
- § 10‑109 and § 10‑116 (Title 24, Part 1) — Requirements referencing Commission‑certified compliance software for performance calculations (referenced by the performance sections).
- § 10‑115 (Title 24, Part 1) — Community shared solar / BESS approval pathway referenced in exceptions.
- Reference Joint Appendix JA2 (climate data) and JA3 (LSC hourly factors) — used by the certified software to produce budgets per § 100.2.
Code references
Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:
§ 100.2 High relevance — show source text
SECTION 100.2—CALCULATION OF ENERGY BUDGETS
Energy budgets are adopted by the Commission to establish the maximum energy consumption that a proposed building, or portion of a building, can be designed to consume. A building complies with the performance standards compliance approach if the energy consumption calculated for the proposed design building is no greater than the energy budget calculated for the standard design building using Commission-certified compliance software as specified by the Alternative Calculation Methods Reference Manual. The energy budget for newly constructed single-family, multifamily, and nonresidential buildings are expressed in terms of Long-Term System Cost (LSC) and Source Energy. The energy budget for additions and alterations for all building types are expressed in terms of LSC.
Long-term System Cost (LSC) is calculated by multiplying for each hour of the year the site energy use (electricity kWh, natural gas therms, or fuel oil or LPG gallons) for each energy type by the applicable CEC-published LSC hourly factors. LSC hourly factors vary for each hour of the year and by energy type (electricity, natural gas, or propane), by Climate Zone and by building type (residential, nonresidential). LSC hourly factors are summarized in Reference Joint Appendix JA3. LSC hourly factors for propane are used for all energy obtained from depletable sources other than electricity and natural gas.
Source Energy is calculated by multiplying for each hour of the year the site energy use (electricity kWh, natural gas therms, or fuel oil or LPG gallons) by Btu factors for fossil fuel consumed either directly at the building site or caused to be consumed to meet the electrical demand of the building considering the long-term marginal hourly resources of Commission-projected electric system resource procurement.
Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code . Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5, 25402.8 and 25943, Public Resources Code .
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FIGURE 100.1-A CALIFORNIA CLIMATE ZONES
Climate Zones for Residential and Nonresidential Occupancies
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2 ALL OCCUPANCIES—MANDATORY REQUIREMENTS FOR THE
MANUFACTURE, CONSTRUCTION AND INSTALLATION OF SYSTEMS, EQUIPMENT AND BUILDING COMPONENTS
SECTION 110.0—SYSTEMS AND EQUIPMENT—GENERAL
Sections 110.1 through 110.12 specify requirements for manufacturing, construction and installation of certain systems, equipment, appliances and building components that are installed in buildings within the scope of Section 100.0(a).
Note: The requirements of Sections 110.0 through 110.12 apply to newly constructed buildings. Sections 141.0 and 150.2 specify which requirements of Sections 110.1 through 110.12 also apply to additions and alterations to existing buildings.
§ 170.0 High relevance — show source text
Exception to Section 170.0 (a)3: If a single development falls in more than one climate zone, all buildings in the subdivision or tract may be designed to meet the performance or prescriptive standards for the climate zone that contains 50 percent or more of the dwelling units.
NOTE: The Commission periodically updates, publishes and makes available to interested persons and local enforcement agencies precise descriptions of the climate zones, as specified in Reference Joint Appendix JA2—Weather/Climate Data.
NOTE: The requirements of Sections 170.1(a) through 170.2(e) apply to newly constructed buildings and Sections 180.1 and 180.2 specify changes to the requirements of Sections 170.1(a) through 170.2(e) that apply to additions or alterations.
NOTE: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code . Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5, 25402.8 and 25943, Public Resources Code .
SECTION 170.1—PERFORMANCE APPROACH
A building complies with the performance approach if the energy consumption calculated for the proposed design building is no greater than the energy budget calculated for the standard design building using Commission-certified compliance software as specified by Sections 10-109 and 10-116 and the Alternative Calculation Method Reference Manual.
(a) Energy budget. The energy budget is expressed in terms of long-term system cost (LSC) and source energy:
- Long-term system cost (LSC). The LSC energy budget is determined by applying the mandatory and prescriptive requirements of the standard design to the proposed design building and has two components, the Efficiency LSC and the Total LSC.
A. The Efficiency LSC energy is the sum of the LSC energy for space-conditioning, water heating, mechanical ventilation, lighting and the self-utilization credit. B. The Total LSC energy is the sum of the Efficiency LSC energy and LSC energy from the photovoltaic system, battery energy storage systems (BESS), and demand flexibility. 2. Source energy. The source energy budget is determined by applying the mandatory and prescriptive requirements of the standard design, except with a consumer gas or propane water heater, to the proposed design building.
Exception to Section 170.1(a): A community shared solar electric generation system, or other renewable electric generation system, and/or community shared BESS, that provides dedicated power, utility energy reduction credits or payments for energy bill reductions to the permitted building and is approved by the Energy Commission as specified in Title 24, Part 1, Section 10-115, may offset part or all of the solar electric generation system or BESS LSC energy required to comply with the standards, as calculated according to methods established by the Commission in the Nonresidential ACM Reference Manual.
(b) Compliance demonstration requirements for performance standards.
- Certificate of Compliance and Application for a Building Permit. The application for a building permit shall include documentation pursuant to Sections 10-103(a)1 and 10-103(a)2 that demonstrates, using an approved calculation method, that the building has been designed so that its source energy and LSC energy consumption do not exceed the standard design energy budgets for the applicable climate zone.
- Field verification of individual dwelling unit systems.
§ 140.0 High relevance — show source text
Note to Section 140.0(c): The Commission periodically updates, publishes and makes available to interested persons and local enforcement agencies precise descriptions of the climate zones, which is available by zip code boundaries depicted in the Reference Joint Appendices along with a list of the communities in each zone.
Note to Section 140.0: The requirements of Sections 140.1 through 140.10 apply to newly constructed buildings. Section 141.0 specifies which requirements of Sections 140.1 through 140.10 also apply to additions or alterations to existing buildings.
Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code. Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5, 25402.8, and 25943, Public Resources Code.
SECTION 140.1—PERFORMANCE APPROACH: ENERGY BUDGETS
A building complies with the performance standards if the energy consumption calculated for the proposed design building is no greater than the energy budget calculated for the standard design building using Commission-certified compliance software as specified by Sections 10-109(c) and 10-116.
(a) Energy budget. The energy budget is expressed in terms of long-term system cost (LSC) and source energy.
- Long-term system cost (LSC). The LSC energy budget is determined by applying the mandatory and prescriptive requirements of the standard design to the proposed design building and has two components, the Efficiency LSC and the Total LSC.
A. The Efficiency LSC energy is the sum of the LSC energy for space-conditioning, water heating, mechanical ventilation, and lighting. B. The Total LSC energy is the sum of the Efficiency LSC energy and LSC energy from the photovoltaic system, battery energy storage systems (BESS) and demand flexibility. 2. Source energy . The source energy budget is determined by applying the mandatory and prescriptive requirements of the standard design to the proposed design building.
Exception to Section 140.1(a). A community shared solar electric generation system, or other renewable electric generation system, and/or community shared BESS, that provides dedicated power, utility energy reduction credits or payments for energy bill reductions to the permitted building and is approved by the Energy Commission as specified in Title 24, Part 1, Section 10-115, may offset part or all of the solar electric generation system or BESS LSC energy required to comply with the standards, as calculated according to methods established by the Commission in the Nonresidential ACM Reference Manual.
Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code. Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5, 25402.8, and 25943, Public Resources Code.
SECTION 140.2—PRESCRIPTIVE APPROACH
To comply using the prescriptive approach a building shall be designed with and shall have constructed and installed systems and components meeting the applicable requirements of Sections 140.3 through 140.10.
§ 10-109 High relevance — show source text
(b) Performance approach. A building complies with the performance approach if the energy consumption calculated for the proposed design building is no greater than the energy budget calculated for the standard design building using Commission-certified compliance software as specified by Sections 10-109(c) and 10-116.
- Energy budget. The energy budget is expressed in terms of source energy and long-term system cost (LSC). A. Long-term system cost (LSC). The LSC energy budget is determined by applying the mandatory and prescriptive requirements of the standard design to the proposed design building and has two components, the Efficiency LSC and the Total LSC.
i. The Efficiency LSC energy is the sum of the LSC energy for space-conditioning, water heating, mechanical ventilation, and the self-utilization credit.
ii. The Total LSC energy is the sum of the Efficiency LSC energy and LSC energy from the photovoltaic system, battery energy storage systems (BESS), lighting, demand flexibility, and other plug loads. B. Source energy. The source energy budget is determined by applying the mandatory and prescriptive requirements of the standard design to the proposed design building. The source energy is the total annual source energy. Exception to Section 150.1(b)1. A community shared solar electric generation system, or other renewable electric generation system, or community shared BESS, which provides dedicated power, utility energy reduction credits, or payments for energy bill reductions to the permitted building and is approved by the Energy Commission as specified in Title 24, Part 1, Section 10-115, may offset part or all of the solar electric generation system and demand flexibility Energy Design Rating required to comply with the Standards, as calculated according to methods established by the Commission in the Residential ACM Reference Manual.
- Compliance demonstration requirements for performance standards. A. Certificate of compliance and application for a building permit. The application for a building permit shall include documentation pursuant to Sections 10-103(a)1 and 10-103(a)2 which demonstrates, using an approved calculation method, that the building has been designed so that its energy consumption does not exceed the standard design energy budgets for the applicable climate zone. Exception to Section 150.1(b)2A Multiple orientation: A permit applicant may demonstrate compliance with the energy budget requirements of Section 150.1(a) and (b) for any orientation of the same building model if the documentation demonstrates that the building model with its proposed designs and features would comply in each of the four cardinal orientations.
B. Field verification. When performance of installed features, materials, components, manufactured devices or systems above the minimum specified in Section 150.1(c) is necessary for the building to comply with Section 150.1(b), or is necessary to achieve a more stringent local ordinance, field verification shall be performed in accordance with the applicable requirements in the following subsections, and the results of the verification(s) shall be documented on applicable certificates of installation pursuant to Section 10-103(a)3 and applicable certificates of verification pursuant to Section 10-103(a)5. i. EER2/SEER2/CEER/HSPF2 Rating. When performance compliance requires installation of a space-conditioning system with a rating that is greater than the minimum rating required by Table 150.1-A or specified for the standard design, the installed system shall be field verified in accordance with the procedures specified in the applicable sections of Reference Residential Appendix RA3.4. ii. **Variable capacity heat pump (VCHP) compliance option.
§ 140.4 High relevance — show source text
MULTI-PASS WATER HEATER is a water heater that the cold water passes through multiple times. The water temperature increases with each pass until the storage tank reaches the intended storage temperature.
SINGLE-PASS WATER HEATER is a water heater which the cold water passes through once and is heated to the intended use temperature.
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ALL OCCUPANCIES—GENERAL PROVISIONS
WEST-FACING (See “orientation.”)
WINDOW FILM is a fenestration attachment product that consists of a flexible adhesive-backed polymer film, which may be applied to the interior or exterior surface of an existing glazing system.
WOOD HEATER is an enclosed wood-burning appliance used for space heating and/or domestic water heating.
WOOD STOVE (See “wood heater.”)
ZONAL describes characterized by or relating to a zone or zones.
ZONE, CRITICAL is a zone serving a process where reset of the zone temperature setpoint during a demand shed event might disrupt the process, including but not limited to computer rooms, data centers, telecom and private branch exchange (PBX) rooms, and laboratories.
ZONE, NONCRITICAL is a zone that is not a critical zone.
ZONE, SPACE-CONDITIONING, is a space or group of spaces within a building with sufficiently similar comfort conditioning requirements so that comfort conditions, as specified in Section 140.4(b)3 or 150.0(h), as applicable, can be maintained throughout the zone by a single controlling device.
SECTION 100.2—CALCULATION OF ENERGY BUDGETS
Energy budgets are adopted by the Commission to establish the maximum energy consumption that a proposed building, or portion of a building, can be designed to consume. A building complies with the performance standards compliance approach if the energy consumption calculated for the proposed design building is no greater than the energy budget calculated for the standard design building using Commission-certified compliance software as specified by the Alternative Calculation Methods Reference Manual. The energy budget for newly constructed single-family, multifamily, and nonresidential buildings are expressed in terms of Long-Term System Cost (LSC) and Source Energy. The energy budget for additions and alterations for all building types are expressed in terms of LSC.
Long-term System Cost (LSC) is calculated by multiplying for each hour of the year the site energy use (electricity kWh, natural gas therms, or fuel oil or LPG gallons) for each energy type by the applicable CEC-published LSC hourly factors. LSC hourly factors vary for each hour of the year and by energy type (electricity, natural gas, or propane), by Climate Zone and by building type (residential, nonresidential). LSC hourly factors are summarized in Reference Joint Appendix JA3. LSC hourly factors for propane are used for all energy obtained from depletable sources other than electricity and natural gas.
Source Energy is calculated by multiplying for each hour of the year the site energy use (electricity kWh, natural gas therms, or fuel oil or LPG gallons) by Btu factors for fossil fuel consumed either directly at the building site or caused to be consumed to meet the electrical demand of the building considering the long-term marginal hourly resources of Commission-projected electric system resource procurement.
§ 150.1 High relevance — show source text
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8 SINGLE-FAMILY RESIDENTIAL BUILDINGS—PERFORMANCE
AND PRESCRIPTIVE COMPLIANCE APPROACHES
SECTION 150.1—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES FOR SINGLE-FAMILY RESIDENTIAL BUILDINGS
(a) Basic requirements. Single-family residential buildings shall meet all of the following:
- The applicable requirements of Sections 110.0 through 110.10.
- The applicable requirements of Section 150.0 (mandatory features).
- Either the performance standards or the prescriptive standards set forth in this section for the climate zone in which the building is located. Climate zones are shown in Reference Joint Appendix JA2–Weather/Climate Data. Exception to Section 150.1(a)3: If a single contiguous subdivision or tract falls in more than one climate zone, all buildings in the subdivision or tract may be designed to meet the performance or prescriptive standards for the climate zone that contains 50 percent or more of the dwelling units. Note: The Commission periodically updates, publishes, and makes available to interested persons and local enforcement agencies precise descriptions of the climate zones, as specified in Reference Joint Appendix JA2–Weather/Climate Data.
Note: The requirements of Sections 150.0(a) through 150.0(r) apply to newly constructed buildings and Sections 150.2(a) and 150.2(b) specifies changes to the requirements of Sections 150.1(a) through 150.1(c) that apply to additions or alterations.
(b) Performance approach. A building complies with the performance approach if the energy consumption calculated for the proposed design building is no greater than the energy budget calculated for the standard design building using Commission-certified compliance software as specified by Sections 10-109(c) and 10-116.
- Energy budget. The energy budget is expressed in terms of source energy and long-term system cost (LSC). A. Long-term system cost (LSC). The LSC energy budget is determined by applying the mandatory and prescriptive requirements of the standard design to the proposed design building and has two components, the Efficiency LSC and the Total LSC.
i. The Efficiency LSC energy is the sum of the LSC energy for space-conditioning, water heating, mechanical ventilation, and the self-utilization credit.
ii. The Total LSC energy is the sum of the Efficiency LSC energy and LSC energy from the photovoltaic system, battery energy storage systems (BESS), lighting, demand flexibility, and other plug loads. B. Source energy. The source energy budget is determined by applying the mandatory and prescriptive requirements of the standard design to the proposed design building. The source energy is the total annual source energy. Exception to Section 150.1(b)1. A community shared solar electric generation system, or other renewable electric generation system, or community shared BESS, which provides dedicated power, utility energy reduction credits, or payments for energy bill reductions to the permitted building and is approved by the Energy Commission as specified in Title 24, Part 1, Section 10-115, may offset part or all of the solar electric generation system and demand flexibility Energy Design Rating required to comply with the Standards, as calculated according to methods established by the Commission in the Residential ACM Reference Manual.
§ 10-109 High relevance — show source text
ELECTRIC VEHICLE SUPPLY EQUIPMENT (EVSE). [BSC-CG, DSA-SS and HCD] The conductors, including the ungrounded, grounded and equipment grounding conductors and the electric vehicle connectors, attachment plugs, personnel protection system, and all other fittings, devices, power outlets or apparatus installed specifically for the purpose of transferring energy between the premises wiring and the electric vehicle.
EMBODIED ENERGY. The energy used for raw material extraction, transportation, manufacturing, assembly, installation and disposal during the life of a product, including the potential energy stored within the product.
ENERGY BUDGET. [CEC] The maximum energy consumption that a proposed building, or portion of a building, can be designed to consume, calculated using CEC-approved compliance software as specified in Section 10-109 of the Energy Code (Title 24, Part 6) and the Alternative Calculation Method (ACM) Reference Manual. The Energy Budget for the newly constructed buildings is expressed in terms of the Long-term System Cost (LSC) and Source Energy. The energy budget for additions and alterations is expressed in terms of LSC.
ENERGY COMMISSION. The California State Energy Resources Conservation and Development Commission. ENERGY EQUIVALENT (NOISE) LEVEL ( L eq ). The level of a steady noise which would have the same energy as the fluctuating noise level integrated over the time period of interest.
ENFORCING AGENCY. The designated department or agency as specified by statute or regulation.
EUTROPHICATION. The excessive growth of aquatic plants, especially algae, producing bacteria which consume nearly all of the oxygen required to sustain fauna and other flora.
EVAPOTRANSPIRATION ADJUSTMENT FACTOR (ETAF). [DSA-SS] An adjustment factor when applied to reference evapotranspiration that adjusts for plant factors and irrigation efficiency, which are two major influences on the amount of water that needs to be applied to the landscape.
EXFILTRATION. The uncontrolled outward air leakage from inside a building, including leakage through cracks and interstices, around windows and doors, and through any other exterior partition or duct penetration.
EXPRESSWAY. An arterial highway for through traffic which may have partial control of access, but which may or may not be divided or have grade separations at intersections.
FILM. [BSC-CG] A material adhered to the first surface of glass (surface 1), perforated or printed with patterns as visual markers.
FLOOR AREA RATIO. Gross square footage of all structures on a site divided by gross square footage of the site.
FOOTPRINT AREA. [DSA-SS] The total area of the furthest exterior wall of the structure projected to natural grade, not including exterior areas such as stairs, covered walkways, patios and decks.
FREEWAY. A divided arterial highway with full control of access and with grade separations at intersections.
FRENCH DRAIN. A trench, hole or other depressed area loosely filled with rock, gravel, fragments of brick or similar pervious material used to collect or channel drainage or runoff water.
GEOTHERMAL. [CEC] Renewable energy generated by deep-earth water or steam.
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DEFINITIONS
§ 130.5 High relevance — show source text
ELECTRICAL POWER DISTRIBUTION SYSTEMS. The following definitions are intended to apply to Section 130.5 only:
ELECTRICAL METERING is a device or system for measuring the electrical power and energy supplied to a customer or premise(s).
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ALL OCCUPANCIES—GENERAL PROVISIONS
EQUIPMENT. A general term, including devices, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation.
LOW VOLTAGE DRY-TYPE DISTRIBUTION TRANSFORMER is a distribution transformer that has an input voltage of 600 volts or less, that is air-cooled, and that does not use oil as a coolant.
PLUG LOAD is the energy consumed by any appliances or electronic device that is plugged into a receptacle or receptacle outlet. Plug loads are not related to general lighting, heating, ventilation, cooling, and water heating, domestic and service water system, renewable power, information technology equipment, computer room electronic equipment, and electric vehicle charging.
SERVICE is the conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premise served.
SERVICE EQUIPMENT is the necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.
ELECTRONICALLY-COMMUTATED MOTOR is a brushless DC motor with a permanent magnet rotor that is surrounded by stationary motor windings, and an electronic controller that varies rotor speed and direction by sequentially supplying DC current to the windings.
EMITTANCE, THERMAL is the ratio of the radiant heat flux emitted by a sample to that emitted by a blackbody radiator at the same temperature.
ENCLOSED SPACE is space that is substantially surrounded by solid surfaces, including walls, ceilings or roofs, doors, fenestration areas, and floors or ground.
ENERGY BUDGET is the maximum energy consumption that a proposed building, or portion of a building, can be designed to consume, calculated using Commission-approved compliance software as specified by Section 10-109 of the Energy Code and the Alternative Calculation Method Reference Manual. The energy budget for newly constructed buildings are expressed in terms of the Long-Term System Cost (LSC) and Source Energy. The energy budget for additions and alterations is expressed in terms of LSC.
ENERGY COMMISSION (CEC) is the California State Energy Resources Conservation and Development Commission.
ENERGY EFFICIENCY RATIO (EER) is the ratio of net cooling capacity (in Btu/hr) to total rate of electrical energy input (in watts), of a cooling system under designated operating conditions, as determined using the applicable test method in the Appliance Efficiency Regulations or Section 110.2.
ENERGY EFFICIENCY RATIO 2 (EER2) is the ratio of the average rate of space cooling capacity (Btu/h) delivered to the average rate of electrical energy consumed by the air conditioner or heat pump as determined in accordance to the test method in 10CFR430 Subpart B Appendix M1. EER is expressed in Btu/Wh.
§ 10-109 High relevance — show source text
EMITTANCE, THERMAL is the ratio of the radiant heat flux emitted by a sample to that emitted by a blackbody radiator at the same temperature.
ENCLOSED SPACE is space that is substantially surrounded by solid surfaces, including walls, ceilings or roofs, doors, fenestration areas, and floors or ground.
ENERGY BUDGET is the maximum energy consumption that a proposed building, or portion of a building, can be designed to consume, calculated using Commission-approved compliance software as specified by Section 10-109 of the Energy Code and the Alternative Calculation Method Reference Manual. The energy budget for newly constructed buildings are expressed in terms of the Long-Term System Cost (LSC) and Source Energy. The energy budget for additions and alterations is expressed in terms of LSC.
ENERGY COMMISSION (CEC) is the California State Energy Resources Conservation and Development Commission.
ENERGY EFFICIENCY RATIO (EER) is the ratio of net cooling capacity (in Btu/hr) to total rate of electrical energy input (in watts), of a cooling system under designated operating conditions, as determined using the applicable test method in the Appliance Efficiency Regulations or Section 110.2.
ENERGY EFFICIENCY RATIO 2 (EER2) is the ratio of the average rate of space cooling capacity (Btu/h) delivered to the average rate of electrical energy consumed by the air conditioner or heat pump as determined in accordance to the test method in 10CFR430 Subpart B Appendix M1. EER is expressed in Btu/Wh.
ENERGY MANAGEMENT CONTROL SYSTEM (EMCS) is an automated control system that regulates the energy consumption of a building by controlling the operation of energy-consuming systems and is capable of monitoring loads and adjusting operations in order to optimize energy usage and respond to demand response signals.
ENERGY OBTAINED FROM DEPLETABLE SOURCES is electricity purchased from a public utility, or any energy obtained from coal, oil, natural gas or liquefied petroleum gases.
ENERGY OBTAINED FROM NONDEPLETABLE SOURCES is energy that is not energy obtained from depletable sources.
ENFORCEMENT AGENCY is the city, county or state agency responsible for issuing a building permit.
ENTHALPY RECOVERY RATIO (ERR) is a ratio of the change in enthalpy of the outdoor air supply to the difference in enthalpy between the entering supply airflow and the entering exhaust airflow, with no adjustment to account for that portion of the psychometric change in the leaving supply airflow that is the result of leakage of entering exhaust airflow rather than exchange of heat or moisture between the airstreams.
ENTIRE BUILDING is the ensemble of all enclosed space in a building, including the space for which a permit is sought, plus all existing conditioned and unconditioned space within the structure.
ENVELOPE (See “Building envelope.”)
EXECUTIVE DIRECTOR is the Executive Director of the Energy Commission.
EXFILTRATION is uncontrolled outward air leakage from inside a building, including leakage through cracks and interstices, around windows and doors, and through any other exterior partition or duct penetration.
EXTERIOR FLOOR/SOFFIT is a horizontal exterior partition, or a horizontal demising partition, under conditioned space. For low-rise residential occupancies, exterior floors also include those on grade.
EXTERIOR PARTITION is an opaque, translucent or transparent solid barrier that separates conditioned space from ambient air or space. For low-rise residential occupancies, exterior partitions also include barriers that separate conditioned space from unconditioned space, or the ground.
§ 10-109 Medium relevance — show source text
DISPOSAL. The management of solid waste through land- filling or transformation at permitted solid waste facilities.
DIVERSION. Activities which reduce or eliminate the amount of solid waste from solid waste disposal for purposes of this code.
ELECTRIC VEHICLE (EV). [BSC-CG, HCD] An automotive-type vehicle for on-road use, such as passenger automobiles, buses, trucks, vans, neighborhood electric vehicles, electric motorcycles and the like, primarily powered by an electric motor that draws current from a rechargeable storage battery, fuel cell, photovoltaic array or other source of electric current. Plug-in hybrid electric vehicles (PHEV) are considered electric vehicles. For purposes of the California Electrical Code, off-road, self-propelled electric vehicles, such as industrial trucks, hoists, lifts, transports, golf carts, airline ground support equipment, tractors, boats and the like, are not included.
ELECTRIC VEHICLE (EV) CAPABLE SPACE. [BSC-CG, DSA-SS and HCD] A vehicle space with electrical panel space and load capacity to support a branch circuit and necessary raceways, both underground and/or surface mounted, to support EV charging.
ELECTRIC VEHICLE (EV) CHARGER. [BSC-CG, HCD] Off-board charging equipment used to charge an electric vehicle.
ELECTRIC VEHICLE CHARGING SPACE (EV SPACE). [HCD] A space intended for future installation of EV charging equipment and charging of electric vehicles.
ELECTRIC VEHICLE CHARGING STATION (EVCS). [BSC-CG, DSA-SS, HCD] One or more electric vehicle charging spaces served by EVSE or receptacle(s).
ELECTRIC VEHICLE (EV) READY SPACE. [HCD] A vehicle space which is provided with a branch circuit; any necessary raceways, both underground and/or surface mounted; to accommodate EV charging, terminating in a receptacle or a charger.
ELECTRIC VEHICLE SUPPLY EQUIPMENT (EVSE). [BSC-CG, DSA-SS and HCD] The conductors, including the ungrounded, grounded and equipment grounding conductors and the electric vehicle connectors, attachment plugs, personnel protection system, and all other fittings, devices, power outlets or apparatus installed specifically for the purpose of transferring energy between the premises wiring and the electric vehicle.
EMBODIED ENERGY. The energy used for raw material extraction, transportation, manufacturing, assembly, installation and disposal during the life of a product, including the potential energy stored within the product.
ENERGY BUDGET. [CEC] The maximum energy consumption that a proposed building, or portion of a building, can be designed to consume, calculated using CEC-approved compliance software as specified in Section 10-109 of the Energy Code (Title 24, Part 6) and the Alternative Calculation Method (ACM) Reference Manual. The Energy Budget for the newly constructed buildings is expressed in terms of the Long-term System Cost (LSC) and Source Energy. The energy budget for additions and alterations is expressed in terms of LSC.
ENERGY COMMISSION. The California State Energy Resources Conservation and Development Commission. ENERGY EQUIVALENT (NOISE) LEVEL ( L eq ). The level of a steady noise which would have the same energy as the fluctuating noise level integrated over the time period of interest.
ENFORCING AGENCY. The designated department or agency as specified by statute or regulation.
§ 170.1 Medium relevance — show source text
A. The Efficiency LSC energy is the sum of the LSC energy for space-conditioning, water heating, mechanical ventilation, lighting and the self-utilization credit. B. The Total LSC energy is the sum of the Efficiency LSC energy and LSC energy from the photovoltaic system, battery energy storage systems (BESS), and demand flexibility. 2. Source energy. The source energy budget is determined by applying the mandatory and prescriptive requirements of the standard design, except with a consumer gas or propane water heater, to the proposed design building.
Exception to Section 170.1(a): A community shared solar electric generation system, or other renewable electric generation system, and/or community shared BESS, that provides dedicated power, utility energy reduction credits or payments for energy bill reductions to the permitted building and is approved by the Energy Commission as specified in Title 24, Part 1, Section 10-115, may offset part or all of the solar electric generation system or BESS LSC energy required to comply with the standards, as calculated according to methods established by the Commission in the Nonresidential ACM Reference Manual.
(b) Compliance demonstration requirements for performance standards.
- Certificate of Compliance and Application for a Building Permit. The application for a building permit shall include documentation pursuant to Sections 10-103(a)1 and 10-103(a)2 that demonstrates, using an approved calculation method, that the building has been designed so that its source energy and LSC energy consumption do not exceed the standard design energy budgets for the applicable climate zone.
- Field verification of individual dwelling unit systems. When performance of installed features, materials, components, manufactured devices or systems above the minimum specified in Section 170.2 is necessary for the building to comply with Section 170.1, or is necessary to achieve a more stringent local ordinance, field verification shall be performed in accordance with the applicable requirements in the following subsections, and the results of the verification(s) shall be documented on applicable Certificates of Installation pursuant to Section 10-103(a)3 and applicable Certificates of Verification pursuant to Section 10-103(a)5. A. EER2/SEER2/CEER/HSPF2 Rating. When performance compliance requires installation of a space-conditioning system with a rating that is greater than the minimum rating required by Table 170.2-K or specified for the standard
2025 CALIFORNIA ENERGY CODE 237
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES
design, the installed system shall be field verified in accordance with the procedures specified in the applicable sections of Reference Residential Appendix RA3. B. Variable capacity heat pump (VCHP) compliance option. When performance compliance requires installation of a heat pump system that meets all the requirements of the VCHP compliance option specified in the ACM Reference Manual, the system shall be field verified in accordance with the procedures in Reference Residential Appendix RA3.4.4.3.
C. Low leakage air handler. When performance compliance requires installation of a low leakage air-handling unit, the installed air handling unit shall be field verified in accordance with the procedures specified in Reference Residential Appendix RA3.1.4.3.9. D. Thermal balancing valve. When performance compliance requires installation of thermal balancing valves with variable speed circulation pump(s), the installation shall meet the procedures specified in Reference Residential Appendix RA4.4.3. E. Heat pump—rated heating capacity.
§ 201.1 Medium relevance — show source text
SECTION A4.201—GENERAL
A4.201.1 Scope. For the purposes of mandatory energy efficiency standards in the California Building Standards Code (Title 24), the California Energy Commission will continue to adopt mandatory standards in the California Energy Code (Title 24, Part 6). It is the intent of these voluntary provisions to encourage local jurisdictions through codification to achieve exemplary performance in the area of building energy efficiency. Local jurisdictions adopting these voluntary provisions as mandatory local energy efficiency standards shall submit the required application and receive the required approval of the California Energy Commission in compliance with Title 24, Part 1, Section 10-106 prior to enforcement. Once the required filing has been verified and finding has been made by the Energy Commission, local jurisdictions shall file an ordinance expressly marking the local modification along with findings and receive the required acceptance from the California Building Standards Commission in compliance with Section 101.7 of this code, prior to enforcement. (Title 24, Part 1, Section 10-106 is available at https://www.energy.ca.gov/programs-and-topics/programs/build- ing-energy-efficiency-standards/2025-building-energy-efficiency
SECTION A4.202—DEFINITIONS
A4.202.1 Definitions. The following terms are defined in Chapter 2.
ENERGY BUDGET.
LONG-TERM SYSTEM COST (LSC).
RECOVERED ENERGY, ON-SITE.
SOLAR POOL HEATING SYSTEM.
SECTION A4.203—PERFORMANCE APPROACH FOR NEWLY CONSTRUCTED BUILDINGS
A4.203.1 Energy efficiency. Newly constructed low-rise residential buildings shall comply with Sections A4.203.1.1 through A4.203.1.4.
A4.203.1.1 Long-term system cost (LSC). LSC rating for the building’s Proposed Design shall be computed by Compliance Software certified by the Energy Commission as specified in Title 24, Part 6, Section 100.1 and 150.1(b), and shall reduce the LSC required in the Compliance Software for minimum performance-based compliance with the California Energy Code by the compliance margin specified in Table A4.203.1.1. The rating shall be included in the Certificate of Compliance documentation.
TABLE A4.203.1.1—RECOMMENDED LSC MARGINS BY CLIMATE ZONES Col2 CALIFORNIA ENERGY CODE CLIMATE ZONE TOTAL LSC COMPLIANCE MARGIN 1 2.70 2 1.62 3 1.10 4 1.11 5 1.01 6 0.24 7 0.24 8 0.21 9 0.20 10 0.18 11 1.11 12 1.05 13 0.96 14 1.21 15 0.59 16 1.68 Note: Community shared options complying with Title 24, Part 1, Section 10-115 may be used to achieve LSC targets. Note: Community shared options complying with Title 24, Part 1, Section 10-115 may be used to achieve LSC targets. 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE APPENDIX A4-9
Frequently asked questions
What is the single most important number I must check when using the performance approach?
Compare the proposed design’s LSC and Source Energy outputs from Commission‑certified software to the standard‑design energy budgets: the proposed values must not exceed the budgets. § 140.1 / § 150.1 / § 170.1 / § 100.2.
Do additions have to meet Source Energy budgets?
No. The energy budget for additions and alterations is expressed in LSC only per § 100.2.
Where do the LSC hourly factors and source‑energy Btu factors come from?
The LSC hourly factors and the source energy Btu factors are published by the CEC and used inside Commission‑certified compliance software (see § 100.2 and Reference Joint Appendix JA3).
Can community shared solar or shared batteries reduce the LSC requirement?
Yes — if approved under the Commission’s process (Title 24 Part 1 § 10‑115) community shared PV/BESS can offset part or all of the PV/BESS LSC energy required; see the exceptions in § 140.1, § 150.1, and § 170.1.
Must I use Commission‑certified software to calculate these budgets?
Yes. The performance sections require calculations be made with Commission‑certified compliance software as specified in Sections 10‑109 and 10‑116 (referenced in the performance sections).
More in California Energy Code
- Compliance paths, energy budgets, performance modeling and forms/software requirements
- Controls, commissioning, demand-response, sensors, and field verification/diagnostic testing
- Domestic hot water systems, efficiency, controls and installation requirements
- Electrical infrastructure, EV charging readiness, load management and demand controls
- Envelope construction, insulation, fenestration and thermal performance
- HVAC systems, ventilation rates, ducting, controls and testing
- Interior and exterior lighting power, controls and daylighting requirements
- Mandatory measures, appliance efficiency and certification requirements
- Photovoltaic requirements, BESS (battery energy storage) sizing and SARA procedures
- Reference appendices, test procedures, product certification and labeling requirements
- Scope, applicability, definitions and administrative requirements
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