Estimate your payback period, annual savings, and 25-year ROI before getting a quote.
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This gives a solid ballpark estimate. Real quotes vary by roof orientation, shading, panel brand, and installer pricing. Use this to understand the range before getting 2–3 real quotes.
A typical UK home uses ~3,500 kWh/year and needs a 3–4 kW system. A US home uses ~10,500 kWh/year and typically needs 6–10 kW. Divide your annual usage by (sun hours × 365) to get your target system size.
Most panels come with a 25-year performance warranty and last 30+ years. Output degrades ~0.5% per year. Our model assumes constant output for simplicity.
In the UK, the Smart Export Guarantee (SEG) pays you for exported electricity. In the US, the federal ITC gives a 30% tax credit on the full installed cost through 2032. In Australia, Small-scale Technology Certificates (STCs) give upfront discounts.
Yes — adding a battery (typically £3,000–£10,000 / $5,000–$15,000) extends payback by 2–4 years but increases self-consumption and protects against outages. Re-run the calculator with the battery cost added to get a combined ROI.
The Solar Panel Calculator estimates the system size you need, how much electricity it will generate, and the savings you could expect. Enter your energy use and local conditions to see whether solar makes sense for your home.
Daily generation is roughly energy (kWh) = systemSize (kW) × peakSunHours × performanceRatio, where the performance ratio (typically about 0.75–0.85) accounts for inverter losses, heat, wiring, and dirt. Peak sun hours are the equivalent hours of full-strength sunlight your location gets on an average day. Working backwards from your daily consumption gives the system size to aim for.
Size a solar system before requesting installer quotes. Estimate the payback period against your current electricity bill. See whether adding a battery improves your savings. Or compare panel counts to fit a system to your available roof space.
It gives a solid estimate based on your usage, system size, and local sun hours. Real output varies with roof angle, shading, weather, and equipment quality.
Divide your daily energy use by your area’s average peak sun hours and typical efficiency losses. Many homes land between 3 kW and 8 kW.
Most panels carry performance warranties of 25 years or more and keep producing beyond that, with a slow annual decline in output.
Many regions offer incentives, tax credits, or feed-in payments. Availability and amounts change, so check your local scheme before you buy.
Yes. A battery lets you store daytime generation for evening use, raising self-consumption and often improving your savings.