Manual J calculator · CA
Manual J load calculation for California.
Reference data for Manual J load calculations in California: ASHRAE design temperatures for 5 top metros, energy code status, and CSLB licensing. The calculator does not load this page's data. It asks for your project location and looks up outdoor design conditions in its own dataset, by IECC 2021 climate zone for a ZIP code or by weather station for the 10 major metros in its city list.
Reference metro
Los Angeles, CA (Los Angeles County) · IECC 2015 zone 3B · winter 99% DB 47°F · summer 0.4% DB 85°F · MCWB 63°F.
0.4% DB: ASHRAE 2021 station value · Manual J 8 loads use the 1% DB
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01 · ASHRAE design conditions
Top 5 metros in California - ASHRAE design temperatures.
These are the ASHRAE 99% heating and 0.4% cooling design temperatures, not the absolute extremes. Outdoor temperatures go past the 0.4% cooling value about 35 hours per year and below the 99% heating value about 88 hours per year.
Manual J 8th edition load calculations use the 1% cooling and 99% heating design temperatures. For ENERGY STAR new homes, the EPA recommends "the ACCA Manual J, 8th edition, 1% cooling season design temperature and 99% heating season design temperature for the weather station that's geographically closest to the home" ( ENERGY STAR, Design Temperature Limits). For the same station the 1% cooling value is exceeded about 88 hours a year, against about 35 for the 0.4% value, so it is the lower of the two, and the table's cooling column is not the Manual J design temperature.
| Metro | County | Zone (IECC 2015) | Winter 99% DB | Summer 0.4% DB | MCWB |
|---|---|---|---|---|---|
| Los Angeles | Los Angeles County | 3B | 47°F | 85°F | 63°F |
| San Francisco Bay Area | San Francisco / Alameda County | 3C | 39°F | 84°F | 64°F |
| San Diego | San Diego County | 3B | 47°F | 85°F | 64°F |
| Sacramento | Sacramento County | 3B | 33°F | 100°F | 70°F |
| Riverside-San Bernardino | Riverside / San Bernardino County | 3B | 39°F | 101°F | 70°F |
Design temperatures are single station values from the ASHRAE 2021 Climatic Design Conditions (99% heating, 0.4% cooling), one airport station per metro, in whole °F within 1°F. DB = dry-bulb. MCWB = mean coincident wet-bulb at the 0.4% cooling design hour.
Zones in this table are from the IECC 2015 county map (PNNL county data). For a ZIP code, BuildSolver's calculator assigns zones by the IECC 2021 county map, which gives the same zones for these counties. A ZIP code near a zone line can get the neighboring zone.
02 · Energy code
Energy code baseline in California is California Title 24 Part 6 (2025 cycle, effective January 1, 2026).
In effect since 2026. Manual J load-calc documentation requirements flow from the state energy code; verify your specific AHJ's submittal rules before relying on the baseline.
- California does not adopt the IECC directly - Title 24 Part 6 is the state-specific energy code, set on a 3-year cycle by the California Energy Commission.
- The 2025 prescriptive path for new single-family homes calls for a heat pump as the space-conditioning system in every CEC climate zone (§150.1(c)6 and Table 150.1-A), or the home must comply through the performance path instead. It is a new-construction rule, not a requirement for replacing a gas furnace.
Code status from California Energy Commission - Building Energy Efficiency Standards (Title 24, Part 6), verified October 7, 2026.
03 · California HVAC labor data
BLS wages and employment for HVAC mechanics in California.
These are state-level wages for occupation code 49-9021 - Heating, Air Conditioning, and Refrigeration Mechanics and Installers - from the most recent BLS Occupational Employment and Wage Statistics release.
- Median hourly wage
- $34.88
- Mean annual wage
- $75,370
- Employment estimate
- 35,130
Wage figures from BLS OEWS May 2025, SOC 49-9021 (state-level), released May 15, 2026.
04 · License & permit
HVAC licensing in California runs through CSLB.
State-level HVAC contractor licensing is administered by the California Contractors State License Board. Licenses renew every 2 years.
License types
- C-20 Warm-Air Heating, Ventilating and Air-Conditioning Contractor
- C-38 Refrigeration Contractor
Permits
California Title 24 Part 6 requires field-verified duct sealing in all climate zones when equipment on an existing ducted system is installed or replaced (§150.2(b)1E, with exceptions such as ducts already documented as sealed), in addition to the standard mechanical permit. When refrigerant-containing components are replaced, refrigerant charge and airflow verification apply to air-cooled air conditioners in CEC Climate Zones 2 and 8 through 15 and to air-source heat pumps in every zone (§150.2(b)1F). A Certificate of Compliance is submitted with the permit application (§10-103(a)1); where field verification applies, the installer's Certificate of Installation is registered with an ECC-Provider and the ECC-Rater issues the Certificate of Verification.
A replacement install typically requires a permit as well.
California's field verification adds an inspection step beyond the standard permit - budget for the ECC-Rater (called a HERS rater in the 2022 code) on change-outs, not just new construction.
05 · FAQ
Common Manual J questions for California contractors.
+Does California's Title 24 require ACCA Manual J?
It requires a load calculation, with Manual J as one of three allowed methods. Title 24 Part 6 (2025) §150.0(h)1 says single-family heating and cooling loads shall be determined with the ASHRAE Handbook, the SMACNA Residential Comfort System Installation Standards Manual, or ACCA Manual J. §150.0(h)5 then requires equipment selection to meet those loads and systems to be sized based on ACCA Manual S-2023. §150.2(b)1C applies §150.0(h) to a complete system replacement, which the code defines as all the system heating or cooling equipment plus a new or replacement duct system. For an equipment-only change-out or a condenser or coil swap, ask the AHJ what documentation it wants. BuildSolver is not ACCA-approved for permit submission. Use its output for sales-phase sizing and client quotes, and produce the permit submittal in ACCA-approved software such as Wrightsoft Right-J8 or Cool Calc Manual J.
+Why is the SF Bay Area in zone 3C?
Zone 3C is the marine-influenced 'warm marine' zone. On the IECC 2021 county map it covers San Francisco, San Mateo, Marin, Santa Clara, Santa Cruz, Monterey, and the central coast, while Los Angeles and San Diego counties are 3B. The Bay Area has mild summers (84°F ASHRAE 0.4% dry-bulb) and mild winters (39°F ASHRAE 99% dry-bulb). For Title 24 sizing, §150.0(h)2 takes outdoor design conditions from Joint Appendix JA2, the ASHRAE Handbook of Fundamentals, or ACCA Manual J, with cooling no greater than the 1.0% dry-bulb and mean coincident wet-bulb, heating no lower than the 99.0% heating dry-bulb or the Heating Winter Median of Extremes, and 75°F cooling and 68°F heating indoors. Manual J 8th edition load calculations use the 1% cooling dry-bulb, which for the same station is at or below the 0.4% value.
+What's a C-20 vs C-38 license?
C-20 is the CSLB Warm-Air Heating, Ventilating and Air-Conditioning classification, the one that covers residential HVAC systems. C-38 is the Refrigeration classification, for equipment that holds products below 50°F, such as commercial refrigeration and cold storage.
+How does Sacramento's design temp differ from coastal California?
Sacramento is inland zone 3B - 100°F ASHRAE 0.4% summer dry-bulb and 33°F 99% winter dry-bulb, about 16°F hotter in summer than the Bay Area. For a Title 24 sizing calculation the cooling design temperature can be no greater than the 1.0% dry-bulb, so the 0.4% value is above that cap; the heating value has to be no lower than the 99.0% heating dry-bulb or the Heating Winter Median of Extremes. Manual J 8th edition load calculations use the 1% cooling dry-bulb as well.
+Is BuildSolver compatible with California's ECC-Rater (HERS) verification process?
BuildSolver provides the Manual J load calculation that feeds into the equipment sizing decision. The ECC-Rater (called a HERS rater in the 2022 code) independently verifies duct sealing and, where the code calls for it, airflow and refrigerant charge at install - that's a separate measurement done by a rater certified by an ECC-Provider. BuildSolver doesn't replace the ECC-Rater or the compliance forms; it gives you a preliminary sizing estimate for the quote.
+Why is the California HVAC wage so much higher than the national median?
BLS OEWS May 2025 (released May 15, 2026) reports a $34.88/hr median in California against $29.33 nationally, about 19% higher, with a California annual mean of $75,370.
Try a California load calculation now.
The chat will ask follow-up questions like an experienced engineer - square footage, construction type, window count, insulation level - and run the Manual J on your inputs. Outdoor design conditions come from its own dataset (by IECC 2021 climate zone for a ZIP code, by weather station for the 10 major metros in its city list), not from the metro table on this page.
Start California calculationRelated · same climate zone
Other states with similar ASHRAE climate zones.
Climate-driven Manual J inputs such as infiltration, latent share, and design temperatures behave similarly across states that share a climate zone. Each page below gives that state's own design temperatures and licensing context. Zones combine the IECC 2015 and IECC 2021 county maps.
Data last reviewed October 16, 2026 · underlying sources as of May 15, 2026