MEP Plans in Orange, CA

Orange project facts we design around

County	Orange County
Title 24 climate zone	Climate Zone 8, confirmed by ZIP for every project
Electric utility (most addresses)	Southern California Edison (SCE)
Permit review	The City of Orange building department
ADU permits issued, 2021–2025	400 (#60 of 450 cities)
ADU approval timeline	Approve or deny within 60 days of a complete application (state law)

ADU building activity in Orange

Orange issued 400 ADU building permits from 2021 through 2025, the 60th most among the 450 California cities that reported ADU permits. Permits went from 56 in 2021 to 88 in 2025.

2021	2022	2023	2024	2025
56	83	69	104	88

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

Title 24 in Climate Zone 8

• Windows: U-factor 0.30 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.
• Solar PV sized by the CEC formula kW = (floor area x 0.586) / 1000 + 1.37; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 734 sq ft or smaller.

Climate Zone 8 requirements in full →

HVAC design for Orange

The California Energy Commission's design-day data for Orange gives the outdoor conditions a Manual J load calculation uses: a summer design temperature of 90°F and a winter design temperature of 33°F.

Summer design (1%)	90°F dry bulb / 68°F wet bulb
Winter design (median of extremes)	33°F
Daily temperature range	27°F
Elevation	194 ft

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 33°F.

Electrical service from Southern California Edison (SCE)

If the load calculation shows you need a service upgrade, a second meter or a relocated service, Southern California Edison (SCE) handles that through its Building, Renovation, and Project Planning Portal, separately from the building permit.

ADU electrical service with Southern California Edison (SCE) →

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.