How Many Solar Panels for 500 kWh a Month?

Answer
11 panels (400 W) · 4.2 kW

With 4.5 peak sun hours and 14% system losses, covering 500 kWh a month takes a 4.25 kW system, or 11 panels of 400 W, needing about 236 sq ft of roof. Sunnier states need fewer panels.

Free, no sign-upInstant resultsUpdated October 2026
kWh
On your utility bill. U.S. average ≈ 860 kWh.
h/day
Southwest 6–7 · South 5 · Midwest 4–4.5 · Northeast 3.5–4
W
%
%
NREL PVWatts default: 14%
System size
–
How we calculated this

    For estimating and educational purposes only. Results are approximate and are not a substitute for a licensed professional, the manufacturer's instructions or your local code. Disclaimer

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    Panels needed by peak sun hours

    Sun hours (region)System size400 W panelsRoof area
    3.5 h (Pacific NW)5.5 kW14301 sq ft
    4.0 h (Northeast)4.8 kW12258 sq ft
    4.5 h (Midwest)4.2 kW11236 sq ft
    5.0 h (Southeast)3.8 kW10215 sq ft
    5.5 h (Texas, Florida)3.5 kW9194 sq ft
    6.0 h (Colorado, SoCal)3.2 kW8172 sq ft
    6.5 h (Arizona, Nevada)2.9 kW8172 sq ft

    Formula: 500 kWh ÷ 30.42 days ÷ (sun hours × 0.86). Check your exact sun hours with NREL PVWatts.

    Frequently asked questions

    How much does a 4.2 kW system produce per year?

    About 5,999 kWh per year at 4.5 sun hours.

    Do bigger panels mean fewer panels?

    Yes. With 450 W panels you would need 10 instead of 11.

    Open the full calculator: Solar Panel Calculator →