Estimate your payback period, annual savings, and 25-year ROI before getting a quote.
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.