How Many Solar Panels Does an ADU Need?

Most California ADUs need between 4 and 10 solar panels (1.5 to 3.5 kW) to meet Title 24. The exact number depends on your ADU's square footage, climate zone, and panel wattage. Here's a quick reference table plus our instant sizing calculator.

Title 24 ADU sizing reference

Using 410W panels (current industry standard) and the 2022 Title 24 formula:

  • 500 sq ft ADU → ~1.0 kW → 3 panels
  • 750 sq ft ADU → ~1.5 kW → 4–5 panels
  • 1,000 sq ft ADU → ~2.0 kW → 5–6 panels
  • 1,200 sq ft ADU (max state ADU size) → ~2.5–3.0 kW → 7–8 panels

Climate zone adjustments

Hotter inland climate zones (CZ 13–15) require more panels per square foot than coastal zones (CZ 6–7) because of higher cooling loads in the energy budget. Our calculator handles this automatically based on your ZIP code.

FAQs

Can I install more panels than required?

Yes, and it's often smart — extra capacity covers EV charging, future heat pump upgrades, and battery charging.

What wattage panels are typical for ADUs?

Most ADU installs use 400–440W residential panels. Higher wattage means fewer panels, more headroom in tight roof areas.

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