Solar Panel Output Calculator 2026 — Daily & Annual kWh
Estimate 2026 solar panel output in kWh per day, month and year from system size, peak sun hours, derate and degradation, using state sun-hour data.
Estimate scope & data quality
- SEO Quick Estimate Uses the inputs available in this calculator.
- Personalized Estimate Use your own bill and location information where this calculator supports it.
- Detailed Solar Economics NOT_COMPUTABLE here without a verified tariff, system design, quote, and eligibility record.
- Data quality
- NOT_AVAILABLE
- Result limitation
- Calculator output is not a source-complete customer result.
A tariff credit is distinct from annual savings. If a result is NOT_COMPUTABLE or CONFLICT, it must not be replaced with an estimate or treated as canonical.
How to use this calculator
- Enter your solar system size in kilowatts (kW). A typical US home system is 6–10 kW.
- Set your daily peak sun hours using the state selector on the right, or enter a custom value. US average is 4.0–5.5 hrs/day.
- Adjust the system efficiency factor (default 82%) — this accounts for inverter losses, wiring losses, shading and temperature.
- Set annual degradation rate (default 0.5%/yr) — this is how much output drops each year due to cell aging.
- Daily, monthly, annual and year-25 production estimates appear instantly.
Understanding your results
How solar output is calculated: Daily output (kWh) = system size (kW) × peak sun hours × efficiency factor. A 7 kW system with 4.5 peak sun hours and 82% efficiency produces 7 × 4.5 × 0.82 = 25.8 kWh per day.
Peak sun hours vs hours of daylight: Peak sun hours are not the same as hours of daylight. Peak sun hours measure the total solar energy received in a day, expressed as equivalent hours of full-intensity sunshine (1,000 W/m²). State averages used on this site range from about 3.1 (Alaska) to 6.5 (Arizona) peak sun hours per day; California averages about 5.8 and Washington about 4.0 (approximate, based on NREL data). Use the state selector to load your local value.
System efficiency factor (derate): Real-world solar systems never achieve 100% of their theoretical output due to: inverter conversion losses (~2%), wiring losses (~2%), soiling/shading (~3–5%), temperature effects (~3–5%) and clipping losses (~1–3%). NREL PVWatts’ default 14% system losses correspond to a factor of 0.86; this site uses 0.82 (82%) to allow for typical real-world losses including some shading.
Annual degradation: Solar panels degrade about 0.3–0.7% per year. At 0.5%/yr, a system producing 10,000 kWh in year 1 produces 9,500 kWh in year 10 and 8,750 kWh in year 25. Most manufacturers guarantee 80% of rated output at 25 years (implying maximum 0.8%/yr degradation).
Seasonal variation: Solar output varies significantly by season. A system producing 30 kWh/day in June may only produce 12 kWh/day in December in northern states. Annual totals are more meaningful than single-day estimates for financial planning. For a site-specific monthly profile, check NREL PVWatts.
Why output matters more in 2026: Until Dec 31, 2025, homeowners could claim 30% of a solar system’s cost under §25D; the One Big Beautiful Bill Act (Public Law 119-21, signed July 4, 2025) ended that credit for systems installed after that date (IRS FAQ). With no credit, payback depends entirely on the kWh your panels produce and what each kWh is worth. Example using the site’s model: 7 kW × 4.5 sun hours × 365 × 0.82 ≈ 9,428 kWh/yr; at 18.19¢/kWh (EIA, July 2026 year-to-date) and a 0.75 bill offset that is about $1,286 in year-1 savings, a roughly 16.3-year simple payback on a $21,000 ($3.00/W) system. In a sunny, high-rate full-net-metering state the same system pays back much faster. This is not tax advice; confirm with a tax professional.
Frequently asked questions
Direct answers for US homeowners.
Related guides
In-depth articles on sizing, costs, and energy decisions.