MEP Plans in Sonoma, CA

Sonoma project facts we design around

County	Sonoma 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 Sonoma building department
ADU permits issued, 2021–2025	57 (#285 of 450 cities)
ADU approval timeline	Approve or deny within 60 days of a complete application (state law)

ADU building activity in Sonoma

Sonoma issued 57 ADU building permits from 2021 through 2025, the 285th most among the 450 California cities that reported ADU permits. Permits went from 22 in 2021 to 4 in 2025.

2021	2022	2023	2024	2025
22	16	4	11	4

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 Sonoma

The California Energy Commission's design-day data for Sonoma gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 94°F and a winter design temperature of 22°F.

Summer design (1%)	94°F dry bulb / 69°F wet bulb
Winter design (median of extremes)	22°F
Daily temperature range	40°F
Elevation	70 ft
Heating degree days	2,998

Both seasons matter here. The heat pump is usually sized for the 94°F cooling condition and then checked to confirm it still covers the heating load at 22°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.