Title 24 · California Energy Code
How are LSC and Source Energy calculated?
In plain terms: the Code requires you to compute both **LSC** and **Source Energy** by multiplying each hour’s site energy (electricity, gas, oil/LPG) by official hourly factors published by the Commission, and then summing those hourly results for the year. Compliance must be demonstrated with Commission‑certified software using those official factors (see §100.2).
Last reviewed: July 6, 2026
What the code requires — plain English
The California Energy Code states the energy budget is expressed as Long‑Term System Cost (LSC) and Source Energy, and that compliance is shown by comparing the proposed design to the standard design using Commission‑certified compliance software. The Code defines how LSC and Source Energy are computed: both are calculated hour‑by‑hour for the year by multiplying the building’s site energy use by published hourly factors (LSC hourly factors for LSC; Btu factors for Source Energy). See §100.2.
The essential rule: compute LSC and Source Energy by summing, for each hour of the year, (site energy × the Commission‑published hourly factor for that energy type). §100.2
Requirements in detail
Basic formulas (plain form)
Long‑Term System Cost (LSC) — sum over each hour of the year of: (site energy by energy type) × (CEC‑published LSC hourly factor for that hour and energy type). LSC hourly factors vary by hour, energy type (electricity, natural gas, propane/other depletable fuels), climate zone and building type. §100.2
Source Energy — sum over each hour of the year of: (site energy by energy type) × (Btu factor that represents fossil fuel consumed directly or caused to be consumed to meet the building’s electrical demand, reflecting Commission‑projected long‑term marginal hourly electric resources). §100.2
The performance compliance demonstration (comparison of proposed vs. standard design using these budgets) must be done with Commission‑certified compliance software (the Alternative Calculation Method / ACM software). §100.2
What inputs matter
- Site energy by hour, for each fuel type: electricity (kWh), natural gas (therms), fuel oil or LPG (gallons). §100.2
- LSC hourly factors published by the CEC (hourly, by energy type, climate zone and building type). §100.2
- Btu factors for source energy that reflect fossil fuel consumption caused directly or indirectly by the building’s loads and the Commission’s long‑term marginal resource mix. §100.2
Where the factors live / special factor rules
- LSC hourly factors are summarized in the Commission’s Reference Joint Appendix JA3 (CEC‑published). Propane (LPG) uses the LSC hourly factors published for propane and, per the Code, propane LSC factors are used for all depletable sources other than electricity and natural gas. §100.2
- Source Energy Btu factors reflect Commission‑projected long‑term marginal hourly resources for the electric system (i.e., marginal resource mix by hour). §100.2
Decision‑relevant summary table
| Decision dimension | Value / rule | Where the Code points you | Code reference |
|---|---|---|---|
| Unit of calculation | Hourly (sum for all hours of year) | Multiply site energy each hour by the appropriate hourly factor | §100.2 |
| LSC factor type | CEC‑published LSC hourly factors (vary by hour, energy type, climate zone, building type) | See Reference Joint Appendix JA3 for factors | §100.2 |
| Source Energy factor type | Hourly Btu factors representing fossil fuel consumed directly or caused by electric demand (marginal resources) | Determined from Commission‑projected long‑term marginal hourly resources | §100.2 |
| Energy types included | Electricity (kWh), natural gas (therms), fuel oil or LPG (gallons) | Multiply each fuel’s site use by its corresponding hourly factor | §100.2 |
| Use of propane LSC factors | Propane factors applied to all depletable sources other than electricity and natural gas | Explicit rule in §100.2 | §100.2 |
| Compliance software | Commission‑certified compliance software must be used for performance compliance | Alternative Calculation Method / ACM software requirement referenced | §100.2 |
Exceptions & special cases
- Additions and alterations: the Code notes that energy budgets for additions/alterations are expressed in LSC (not necessarily both metrics for every project type); check the applicable chapter for building type (e.g., residential, nonresidential) for how budgets are expressed. §100.2
- Propane / other depletable fuels: the Code treats propane LSC factors as the proxy for all non‑electric, non‑natural‑gas depletable sources. §100.2
- Source Energy factors are not simple site‑to‑source conversion constants — they are hour‑specific Btu factors that incorporate projected marginal electric resource procurement; the Code requires using the Commission‑determined values (not ad hoc multipliers). §100.2
(For other exceptions that alter the energy budget, such as community‑shared solar offsets, see the performance sections for each occupancy; those provisions reference community shared options that may offset parts of the LSC or source energy budget — see §150.1 and §140.1 for how energy budgets are applied for single‑family and nonresidential buildings.) §150.1 §140.1
Common mistakes
- Treating LSC and Source Energy as single, static annual multipliers rather than hour‑by‑hour sums. The Code requires hourly multiplication and summing for the full year. §100.2
- Using generic or locally chosen conversion factors for source energy (e.g., a single kWh→Btu factor) instead of the Commission’s marginal‑hourly Btu factors. §100.2
- Forgetting that LSC hourly factors vary by climate zone and building type — using the wrong zone or building class will distort the LSC budget. §100.2
- Attempting to calculate compliance outside Commission‑certified software. The performance approach comparison must be done using Commission‑certified compliance software / ACM methods. §100.2
Worked example (illustrative — factors shown are hypothetical)
Important: the Code does NOT publish numeric hourly LSC or Btu factors in §100.2; it directs you to use the CEC‑published hourly factors and Commission‑certified software. The numbers below are a simple, hypothetical illustration only — do not use them for compliance.
Scenario (hypothetical):
- Building annual site electricity = 10,000 kWh (assume distributed uniformly = 10,000 / 8,760 ≈ 1.14 kWh per hour).
- Building annual gas = 120 therms (assume uniformly ≈ 0.0137 therm per hour).
- Hypothetical hourly factors (NOT CODE values): assume an LSC hourly factor for electricity = 0.20 (units = LSC‑units per kWh) for each hour, and LSC hourly factor for natural gas = 2.5 (LSC‑units per therm) for each hour. For Source Energy, assume Btu factor for electricity (marginal) = 3,500 Btu per kWh and for gas = 100,000 Btu per therm (hypothetical illustrative numbers).
Steps (illustrative):
- Hourly LSC contribution from electricity = 1.14 kWh × 0.20 = 0.228 LSC‑units per hour. Annual (×8,760) ≈ 1,997 LSC‑units.
- Hourly LSC from gas = 0.0137 therm × 2.5 = 0.0343 LSC‑units per hour. Annual ≈ 300 LSC‑units.
- Total annual LSC (illustrative) = 1,997 + 300 = 2,297 LSC‑units. (Actual LSC uses the CEC hourly factors and sums hour‑by‑hour across the year.) §100.2
For Source Energy (illustrative):
- Hourly source Btu from electricity = 1.14 kWh × 3,500 Btu/kWh = 3,990 Btu/hr. Annual ≈ 34.9 million Btu.
- Hourly source Btu from gas = 0.0137 therm × 100,000 Btu/therm = 1,370 Btu/hr. Annual ≈ 12.0 million Btu.
- Total annual Source Energy (illustrative) ≈ 46.9 million Btu. (Real Source Energy uses Commission Btu factors that vary by hour.) §100.2
Reminder: the Code requires the use of the Commission’s published hourly factors and compliance software — do not substitute your own numeric factors for compliance. §100.2
Related provisions
- §150.1 — Performance and prescriptive compliance approaches for single‑family residential buildings (energy budget expressed in LSC and Source Energy; community shared offsets exception noted). §150.1
- §140.1 — Performance approach: energy budgets for nonresidential buildings expressed in LSC and Source Energy. §140.1
- §170.1 — Performance approach for other occupancies (LSC and Source Energy rules referenced for specific occupancy types). §170.1
- Reference Joint Appendix JA3 — location where the CEC summarizes LSC hourly factors (see §100.2 directing you to the CEC‑published LSC hourly factors). §100.2
Code references
Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:
§ 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.
§ 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.
§ 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.
§ 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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ALL OCCUPANCIES—GENERAL PROVISIONS
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.
§ 140.4 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.
§ 140.1 High relevance — show source text
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.
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 140.3—PRESCRIPTIVE REQUIREMENTS FOR BUILDING ENVELOPES
A building complies with this section by being designed with and constructed to meet all prescriptive requirements in Subsection (a) and the requirements of Subsection (c) and (d) where they apply.
(a) Envelope component requirements.
- Exterior roofs and ceilings. Exterior roofs and ceilings shall comply with each of the applicable requirements in this subsection:
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NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE
COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY
A. Roofing products. Shall meet the requirements of Section 110.8 and the applicable requirements of Subsections i through ii: i. Nonresidential buildings: a. Low-sloped roofs in climate zones 1 through 16 shall have:
- A minimum aged solar reflectance of 0.63 and a minimum thermal emittance of 0.75; or
- A minimum solar reflectance index (SRI) of 75.
§ 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 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.
2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 2-5
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
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).
2025 CALIFORNIA ENERGY CODE 13
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
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
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.
Frequently asked questions
What exactly is the difference between LSC and Source Energy?
LSC measures the long‑term system cost impact of a building’s hourly site energy use by multiplying site energy by CEC‑published LSC hourly factors and summing hourly; Source Energy measures the total annual Btu consumption caused directly or indirectly by the building (using Commission Btu factors tied to marginal hourly electric resources). §100.2
Do I need to perform hourly calculations myself?
No — the Code requires use of Commission‑certified compliance software that implements the hour‑by‑hour calculations and the official CEC hourly factors. §100.2
Can I use a single multiplier to convert site energy to source energy for the whole year?
No. Source Energy uses hourly Btu factors reflecting marginal electric resources by hour; the Code requires hour‑by‑hour multiplication and summation. §100.2
Where do I find the LSC hourly factors?
The Code points to the CEC‑published values summarized in Reference Joint Appendix JA3; the compliance software uses those official factors. §100.2
How are depletable fuels other than natural gas handled?
The Code directs that propane (LPG) LSC hourly factors are used as the factor for all depletable sources other than electricity and natural gas. §100.2
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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