Free solar panel calculator. Estimate system size, number of panels needed, installation cost, payback period, ROI, and environmental impact for residential solar.
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Going solar is one of the smartest investments for your home. Our solar panel calculator helps you determine the ideal system size, estimate costs with the 30% federal tax credit, and project your long-term savings. Whether you want to offset 50% or 100% of your electricity bill, this calculator provides accurate estimates based on your location and energy usage.
Solar panel sizing depends on your electricity consumption, local sun exposure (peak sun hours), and system efficiency. The calculator divides your annual energy needs by the production capacity of solar panels in your region. Typical residential systems range from 4kW to 12kW, using 10-30 panels depending on panel wattage and roof space.
System Size Formula
System Size (kW) = Annual kWh รท (Peak Sun Hours ร 365 ร Efficiency)Avoid overpaying for an oversized system or underproducing with a system that's too small.
Understand upfront costs, tax credits, payback period, and 25-year savings before committing.
Use your calculations to evaluate installer quotes and ensure you're getting fair pricing.
See exactly how much carbon dioxide your solar system will offset over its lifetime.
Calculate solar before buying to factor energy costs into your budget.
Determine if solar can significantly reduce your $200+ monthly bills.
Size a system to cover both home usage and EV charging needs.
Perfect time to add solar - save on future installation costs.
The average US home uses 900 kWh/month and needs a 6-8 kW system, which is about 15-20 panels (at 400W each). Your specific needs depend on electricity usage, sun exposure, and panel efficiency. Use our calculator with your actual utility bill for accurate results.
The Investment Tax Credit (ITC) allows you to deduct 30% of your solar installation cost from federal taxes through 2032. For a $20,000 system, you'd save $6,000. The credit drops to 26% in 2033 and 22% in 2034. This is a tax credit, not a deduction, meaning dollar-for-dollar savings.
The average payback period is 6-10 years, depending on electricity rates, sun exposure, and incentives. In high-rate states like California or Hawaii, payback can be 5 years or less. After payback, you're essentially getting free electricity for 15-20+ years.
Peak sun hours measure the intensity of sunlight, not total daylight. One peak sun hour = 1 kWh of solar energy per square meter. The US Southwest gets 6-7 hours, Southeast 5-6 hours, Northeast 4-5 hours, and Pacific Northwest 3.5-4.5 hours. Our calculator includes regional presets.
Yes, but at reduced efficiency (10-25% of rated output). Our calculator accounts for this through system efficiency (typically 80%). Annual production estimates factor in weather patterns. Battery storage helps maximize self-consumption during variable conditions.
Average installed cost is $2.50-$3.50 per watt before incentives. A typical 8kW system costs $20,000-$28,000 gross, or $14,000-$19,600 after the 30% federal tax credit. Prices vary by location, installer, and equipment quality. Premium panels and batteries cost more.