Estimate consumption
We combine a baseline for your home size with the appliances you select to estimate monthly kilowatt-hours, or you can replace that estimate with actual kWh.
Free appliance-aware solar panel calculator
How many solar panels do you actually need?
Choose your home and appliances. Get a useful estimate in seconds—then adjust the assumptions to match your roof and location.
1
Tell us about your home
Start with the closest size.
2
What do you power?
Select everyday and high-energy loads.
Fine-tune the estimate location, panel size & offset
What the number means
A useful estimate, built from the loads that matter.
Bedroom count is only a starting point. Electric heating, water heating, dryers, vehicles and pools can move the answer dramatically.
Account for real output
Panel wattage is adjusted for your peak sun hours and a 20% allowance for heat, wiring, inverter and other losses.
Round up and verify
Your annual energy target is divided by estimated output per panel and rounded up. Then verify roof fit, shade and utility rules.
Annual electricity target÷Annual output per panel=Panels needed
Quick guide
Typical planning ranges
These examples use 400-watt panels, five peak sun hours per day and 20% system losses. Your calculator choices are more useful than these broad ranges.
Small apartment / essential loads6–10 panels≈ 2.4–4.0 kW
2-bedroom home / washer + dryer + HVAC14–18 panels≈ 5.6–7.2 kW
Large all-electric home22–34 panels≈ 8.8–13.6 kW
Direct answers
Solar calculator questions
Transparent planning answers—not a sales quote.
Should I use my electric bill instead of bedroom count?
Yes. Twelve months of electricity usage in kWh is the strongest starting point because it measures the energy your solar system would need to replace. Bedroom count and appliances are planning estimates when bills are unavailable.
Will the estimated number of panels fit on my roof?
Not necessarily. Chimneys, vents, roof orientation, fire setbacks, shade and structural condition determine usable roof area. Watt My Roof estimates energy sizing; an installer must verify the physical layout.
Will this estimate match my utility's approved system size?
Not always. Net-metering rules, export rates, system-size caps and interconnection requirements vary by utility. Confirm current local rules before relying on an estimated panel count or savings claim.
How accurate is the Watt My Roof calculator?
It is a transparent planning estimate, not an installation design. The calculator shows its energy-use, sunlight, panel-wattage and 20% system-loss assumptions, requires no signup, and lets you replace estimates with your actual monthly kWh.
Solar sizing guides
Answers for the way people actually plan a system.
Go deeper by home size, appliance load, sunlight, electric bill or original calculator data.
Roof fit
How many solar panels can fit on my roof?
Estimate roof capacity from usable square footage, panel size, sun hours and your monthly kWh target.
Calculate roof fit →Sunlight dataHow peak sun hours change panel count
See modeled solar panel counts across 3.0–6.0 peak sun hours and 500–2,000 kWh per month.
Compare sun hours →Original dataSolar panels needed by monthly kWh
Compare citable modeled panel counts from 250–3,000 kWh per month across common sun-hour assumptions.
View monthly kWh data →2,000 kWh dataHow many panels for 2,000 kWh per month?
Use a high-consumption modeled example to compare panel count, system size and roof-fit limits.
View 2,000 kWh data →1,000 kWh dataHow many panels for 1,000 kWh per month?
Compare modeled panel counts across 3.0–6.0 peak sun hours with transparent calculator assumptions.
View the data →2026 incentivesWhat solar incentives are actually left?
Calculate net cost after verified state, utility and local programs—and understand what happened to the federal 30% credit.
Check 2026 incentives →Electric billCalculate solar panels from your electric bill
Convert your monthly bill and electricity rate into estimated kWh, panels and system size.
Calculate from your bill →Square footageSolar panels needed by home size
Compare planning ranges for 1,000, 1,500, 2,000, 2,500 and 3,000 square foot homes.
Compare home sizes →Home sizeHow many solar panels for a 2-bedroom home?
A worked example with a refrigerator, washer, electric dryer and central HVAC.
Read the guide →AppliancesHow many panels do common appliances add?
Why an electric dryer, water heater, EV or pool can change the answer.
Compare appliance loads →FormulaHow to calculate the number of solar panels
The transparent kWh, sun-hour, panel-wattage and system-loss formula.
See the calculation →Independent planning first. Future product recommendations may use affiliate links, clearly labeled when added. Calculator results are never changed to favor a product. Read our affiliate disclosure.