Tool 02 · Panels
How many solar panels do I need?
Turn monthly electricity use into system size, panel count and rough roof area. Built for the exact search homeowners type before they ask for quotes.
State-capital 2024 GHI is resource context, not an address or roof measurement. The state yield uses GHI×365×0.72; enter a roof-specific yield above to override it. Shading, direction and tilt must already be included in that estimate. The sun look-up is regional context, not a roof survey.
Use this free panel count calculator to turn monthly electricity use into a rough solar system size, number of panels and roof-area estimate. Enter kWh use, panel wattage and a sun assumption for an instant planning result.
No email required. Instant browser-based planning math with clear assumptions.
What changes the answer?
Panel count is not magic: annual kWh ÷ expected production per kW ÷ panel wattage. Pick your state so sun is a place name, not a vague “high/low” label.
Roof area shows module footprint and a nearly estimate that adds about 1 meter (3.28 ft) of access margin: (√sqft + 3.28)² × 1.05. Shading, tilt and fire setbacks still move the real number — confirm with the sun look-up and a quote scorecard.
What this tool estimates
Use this free panel count calculator to turn monthly electricity use into a rough solar system size, number of panels and roof-area estimate. Enter kWh use, panel wattage and a sun assumption for an instant planning result.
No email required. Results are calculated in your browser; use them as a planning estimate, not a guaranteed quote or savings forecast.
How the math works
The tool converts monthly kWh into annual use, divides it by an annual production assumption to estimate system size, then divides by selected panel wattage. Roof-area output is a rule-of-thumb planning frame, not a layout or engineering plan.
Key variables that change your result
Monthly electricity use
Twelve months of kWh is more reliable than one bill because cooling and heating loads can be seasonal.
Panel wattage
Higher-watt panels can reduce panel count, but roof geometry and equipment choice still matter.
Solar production assumption
Production varies by sun resource, roof direction, tilt, weather and shading.
Questions homeowners ask
How many solar panels does an average home need?
What information do I need for a panel count estimate?
Does this include roof shading?
State context matters
Find your state solar guide
Costs, incentives, export rules and payback inputs vary by state. Open your state guide before treating any calculator result as a buying decision.