I built this calculator because most "solar estimates" are just lead-gen forms in disguise. This one gives you real numbers — system size, cost, payback, 25-year ROI — before you talk to anyone.
Four fields. No email. Takes about 30 seconds.
Compare up to 3 bids from pre-vetted local installers. Free, no obligation — and you'll know if their numbers match mine.
Get free quotes from local installers →Affiliate link — I may earn a commission. Your quotes are free.
12 questions to ask every installer before signing. Plus red flags I've seen in real contracts. I'll email it immediately — no drip campaigns, no spam.
I send ~2 emails/month on solar policy changes and deals. Unsubscribe anytime.
I'm not a solar installer — I'm a researcher who got frustrated with black-box solar calculators. Here's exactly what's under the hood:
I estimate your monthly electricity consumption (kWh) from your bill using state average electricity rates from US EIA monthly data. Then I divide annual consumption by the product of state peak sun hours (from NREL's PVWatts) × 365 × 0.8 efficiency factor to arrive at the required array size in kW.
Based on EnergySage's quarterly state-by-state cost-per-watt averages, derived from their installer quote marketplace. I apply a multiplier for non-standard roof types (tile +8%, metal +3%, flat +5%) based on industry-reported install complexity premiums.
I assume the system offsets 90% of your annual electricity consumption, accounting for system losses. Savings are calculated at your state's current electricity rate with a 3% annual escalator, consistent with EIA long-term electricity price projections.
Net cost after the federal ITC (30%) is subtracted from cumulative savings over 25 years. Savings are escalated at 3%/year for electricity inflation and reduced at 0.5%/year for panel degradation — both industry-standard assumptions.