MEP Plans in Walnut Creek, CA

Walnut Creek project facts we design around

County	Contra Costa County
Title 24 climate zone	Climate Zone 12, confirmed by ZIP for every project
Electric utility (most addresses)	Pacific Gas and Electric (PG&E)
Permit review	The City of Walnut Creek building department
ADU permits issued, 2021–2025	139 (#178 of 450 cities)
ADU approval timeline	Approve or deny within 60 days of a complete application (state law)

ADU building activity in Walnut Creek

Walnut Creek issued 139 ADU building permits from 2021 through 2025, the 178th most among the 450 California cities that reported ADU permits. Permits went from 26 in 2021 to 27 in 2025.

2021	2022	2023	2024	2025
26	24	21	41	27

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

Title 24 in Climate Zone 12

• 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%).
• Whole-house fan required (at least 1.5 cfm per square foot of floor area); units of 500 sq ft or less are exempt.
• Cool roof required: steep-sloped roofs need aged solar reflectance 0.2 or higher and thermal emittance 0.75 or higher.
• Solar PV sized by the CEC formula kW = (floor area x 0.613) / 1000 + 1.4; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 653 sq ft or smaller.

Climate Zone 12 requirements in full →

HVAC design for Walnut Creek

The California Energy Commission's design-day data for Walnut Creek gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 92°F and a winter design temperature of 23°F.

Summer design (1%)	92°F dry bulb / 67°F wet bulb
Winter design (median of extremes)	23°F
Daily temperature range	32°F
Elevation	245 ft

Both seasons matter here. The heat pump is usually sized for the 92°F cooling condition and then checked to confirm it still covers the heating load at 23°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.