California's Title 24 energy code divides the state into 16 climate zones. Climate Zone 15 (Low Desert) covers Palm Springs, Indio, El Centro, Coachella, Imperial Valley. Your zone determines the exact kW per square foot of conditioned floor area required on a new ADU.
Title 24 multiplies your ADU's conditioned floor area by a climate-zone-specific kW factor to set the minimum required solar system size. Among the highest solar irradiance in the country (~1,900 kWh/kW/year). Heat derating slightly reduces panel efficiency.
Most ADUs in Climate Zone 15 land in the 2.2–5.0 kW range — typically 4 to 10 modern (~400W) panels.
Annual solar production in Climate Zone 15 is driven by local irradiance, temperature, and shading. Among the highest solar irradiance in the country (~1,900 kWh/kW/year). Heat derating slightly reduces panel efficiency. Expect roughly 1,400–1,700 kWh per installed kW per year for typical south-facing roofs.
Title 24-compliant ADU solar packages range from $4,000 to $15,000 in Climate Zone 15. Pricing is driven primarily by system size, panel quality, and battery — not climate zone itself. HDM financing typically reduces effective cost by ~40%.
Climate Zone 15 (Low Desert) covers Palm Springs, Indio, El Centro, Coachella, Imperial Valley. The California Energy Commission publishes the full ZIP-to-zone mapping.
Climate zones with hotter summers or more cloud cover tend to require slightly larger systems per square foot. Climate Zone 15 ADUs typically need 2.2–5.0 kW.
Yes — enter your ZIP code on our solar cost calculator. We map every California ZIP to its Title 24 climate zone automatically.