MEP Plans in Napa, CA
Permit-ready mechanical, electrical and plumbing plans for ADUs, garage conversions, additions and single-family homes in Napa, prepared for plan check at the City of Napa building department, with Title 24 available in the same order.
Napa project facts we design around
| County | Napa County |
|---|---|
| Title 24 climate zone | Climate Zone 2, confirmed by ZIP for every project |
| Electric utility (most addresses) | Pacific Gas and Electric (PG&E) |
| Permit review | The City of Napa building department |
| ADU permits issued, 2021–2025 | 303 (#93 of 450 cities) |
| ADU approval timeline | Approve or deny within 60 days of a complete application (state law) |
ADU building activity in Napa
Napa issued 303 ADU building permits from 2021 through 2025, the 93rd most among the 450 California cities that reported ADU permits. Permits went from 60 in 2021 to 73 in 2025.
| 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|
| 60 | 50 | 61 | 59 | 73 |
Source: California Department of Housing and Community Development, Annual Progress Report data (ADU building permits by year).
Title 24 in Climate Zone 2
- Windows: U-factor 0.27 or lower and solar heat gain coefficient (SHGC) 0.23 or lower, with total window area up to 20% of floor area (west-facing up to 5%).
- Solar PV sized by the CEC formula kW = (floor area x 0.621) / 1000 + 1.22; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 934 sq ft or smaller.
Climate Zone 2 requirements in full →
HVAC design for Napa
The California Energy Commission's design-day data for Napa gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 90°F and a winter design temperature of 26°F.
| Summer design (1%) | 90°F dry bulb / 67°F wet bulb |
|---|---|
| Winter design (median of extremes) | 26°F |
| Daily temperature range | 29°F |
| Elevation | 60 ft |
| Heating degree days | 2,749 |
Both seasons matter here. The heat pump is usually sized for the 90°F cooling condition and then checked to confirm it still covers the heating load at 26°F.
Electrical service from Pacific Gas and Electric (PG&E)
If the load calculation shows you need a service upgrade, a second meter or a relocated service, Pacific Gas and Electric (PG&E) handles that through its Your Projects portal, separately from the building permit.
ADU electrical service with Pacific Gas and Electric (PG&E) →
Plumbing and sewer
The plumbing plan shows the route, slope and cleanouts of the connection to the existing sewer lateral.
Pricing is flat statewide: ADU plans from $995, full ADU MEP package from $2,295, Title 24 add-on $240. See what's in a complete ADU MEP set.
Nearby places compared
| Place | Climate zone | Electric utility | ADU permits 2021–25 |
|---|---|---|---|
| St. Helena | CZ 2 | Pacific Gas and Electric (PG&E) | 62 |
| American Canyon | CZ 2 | Pacific Gas and Electric (PG&E) | 45 |
| Calistoga | CZ 2 | Pacific Gas and Electric (PG&E) | 27 |
| Yountville | CZ 2 | Pacific Gas and Electric (PG&E) | 13 |
Guides for Napa projects
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Start My OrderGeneral guidance, not legal advice. Climate zone and utility are shown for most addresses in Napa; requirements vary by project. Confirm with the City of Napa building department.