Modesto Climate Zone & Energy Code

Climate Zone: CEC Climate Zone 12 (northern Central Valley). IECC Climate Zone 3B (hot-dry). Modesto's climate is similar to Sacramento — hot, dry summers and mild winters — typical of the Central Valley's demanding HVAC climate.

Energy Code & Manual J Requirement: California Title 24 Part 6 (2025 edition, effective January 1, 2026). ACCA Manual J required for residential HVAC sizing. City of Modesto and Stanislaus County enforce Title 24. Adjacent Merced County is also subject to full Title 24 enforcement.

Local Electric Utility: Pacific Gas & Electric (PG&E)

Building Department: City of Modesto Development Services Department

Local Trade Association: ACCA California / ASHRAE San Joaquin Valley Chapter