MEP Plans in Vallejo, CA

Vallejo project facts we design around

County	Solano County
Title 24 climate zone	Climate Zone 3 (with parts in CZ 12), confirmed by ZIP for every project
Electric utility (most addresses)	Pacific Gas and Electric (PG&E)
Permit review	The City of Vallejo building department
ADU permits issued, 2021–2025	178 (#145 of 450 cities)
ADU approval timeline	Approve or deny within 60 days of a complete application (state law)

ADU building activity in Vallejo

Vallejo issued 178 ADU building permits from 2021 through 2025, the 145th most among the 450 California cities that reported ADU permits. Permits went from 36 in 2021 to 29 in 2025.

2021	2022	2023	2024	2025
36	35	35	43	29

Source: California Department of Housing and Community Development, Annual Progress Report data (ADU building permits by year).

Title 24 in Climate Zone 3

• Windows: U-factor 0.27 or lower (no SHGC limit in this zone), with total window area up to 20% of floor area.
• Solar PV sized by the CEC formula kW = (floor area x 0.628) / 1000 + 1.12; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 1,083 sq ft or smaller.

Climate Zone 3 requirements in full →

HVAC design for Vallejo

The California Energy Commission's design-day data for Vallejo gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 88°F and a winter design temperature of 28°F.

Summer design (1%)	88°F dry bulb / 66°F wet bulb
Winter design (median of extremes)	28°F
Daily temperature range	23°F
Elevation	85 ft

Both seasons matter here. The heat pump is usually sized for the 88°F cooling condition and then checked to confirm it still covers the heating load at 28°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. Some Bay Area cities also have private sewer lateral inspection rules, so ask whether your project triggers one.

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.