Solar Savings Calculator
Find out how much a solar panel system will save and when it pays back. Enter system size, local sun hours, your electricity rate, and installation cost to see annual savings and 25-year ROI.
Calculate Solar Savings
US avg: 4–5h, UK: 2.5–3h, Australia: 5–6h
Typically 75–85% after all losses
Feed-in tariff or SEG payment if you export surplus
% of solar production you use directly
Solar Investment Analysis
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Annual Production (kWh)
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Annual Savings
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Payback Period (years)
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25-Year Net Savings
Formulas
Annual kWh = kW × sun_hours × 365 × (efficiency ÷ 100)
Self-use savings = Annual kWh × (self_use ÷ 100) × rate
Export savings = Annual kWh × (1 − self_use ÷ 100) × export_tariff
Total annual savings = Self-use savings + Export savings
Payback (years) = Installation cost ÷ Annual savings
25-year net = (Annual savings × 25) − Installation cost
Self-use savings = Annual kWh × (self_use ÷ 100) × rate
Export savings = Annual kWh × (1 − self_use ÷ 100) × export_tariff
Total annual savings = Self-use savings + Export savings
Payback (years) = Installation cost ÷ Annual savings
25-year net = (Annual savings × 25) − Installation cost
Peak Sun Hours by Region
| Location | Peak Sun Hours/Day |
|---|---|
| Arizona, Nevada, Southern Spain | 5.5–7.0 |
| California, Texas, Italy, Greece | 4.5–6.0 |
| Florida, Australia (most) | 4.5–5.5 |
| Mid-Atlantic USA, France | 4.0–5.0 |
| Pacific NW USA, Germany, Netherlands | 3.0–4.0 |
| UK (South) | 2.8–3.5 |
| UK (North), Scandinavia | 2.0–2.8 |
Frequently Asked Questions
How do I calculate solar panel savings?
Annual production (kWh) = System kW × daily sun hours × 365 × system efficiency. Savings = (self-consumed kWh × electricity rate) + (exported kWh × feed-in tariff). Payback = installation cost ÷ annual savings. A 6 kW system at 4.5 sun hours, 80% efficiency produces 6 × 4.5 × 365 × 0.8 = 7,884 kWh/year.
How many peak sun hours does my location get?
Peak sun hours represent equivalent hours of full 1,000 W/m² solar irradiance — not daylight hours. Locations closer to the equator and with clearer skies get more. Tools like PVWatts (NREL) or PVGIS (EU) give precise values for any location. Use a conservative value (lower end of range) for more realistic estimates.
What is a realistic solar panel system efficiency?
Panel-rated efficiency (typically 20–22% for premium panels) converts sunlight to DC power. System efficiency also accounts for inverter losses (~2–5%), wiring losses (~1–3%), temperature derating in hot weather (~5–10%), soiling and shading (~5–10%). Total system efficiency from sunlight to AC outlet is typically 75–85%.
Is solar worth it?
In most sunny regions with electricity rates above $0.12/kWh, solar typically pays back in 5–10 years with 15–20 years of free electricity after that. UK payback is typically 8–12 years. With battery storage, payback extends but energy independence increases. Rising electricity rates improve the financial case over time. For most homeowners, solar is a solid long-term investment.