Does the federal tax credit make a big difference to payback?

Yes — significantly. The 30% Residential Clean Energy Credit can shave 2-4 years off your payback period on a typical $25,000 system. The credit was extended through 2032 by the Inflation Reduction Act.

Solar Payback Period Calculator

Two questions, real answer. We use NREL sun-hour data and EIA electricity rates by state — no need to know technical inputs.

What state are you in? We use this to pull your state's average sun hours and electricity rate.

Monthly electric bill ($) Your average — look at a recent bill (electric portion only, not water/gas).

Annual kWh used (optional, but big accuracy boost) If your state's avg rate doesn't match your real rate (common with municipal utilities), enter your actual annual usage instead. Most bills show 12-month total — or multiply daily avg × 365.

All values below are auto-filled from your state's averages — override only if you have actual quotes or know your usage.

Electricity rate ($/kWh) FROM STATE EIA state average. Override if your utility differs.

Daily peak sun hours FROM STATE NREL state average. AZ ~6.5, WA ~3.6, FL ~5.4.

System size (kW) AUTO-SIZED We size to cover ~100% of your annual usage.

Installed cost ($/watt) FROM STATE SEIA/Wood Mackenzie state avg. CA ~$3.85, AZ ~$2.70, NY ~$3.55.

Electricity inflation %/yr EIA 20-yr avg ≈ 3.5%.

Federal tax credit (%) 30% through 2032 (IRA).

State / utility rebate ($) DSIRE lists state programs.

Net metering policy FROM STATE CA (NEM 3.0), HI, NV, AZ, LA, KS, KY, IN, MS, OK, TN, UT now use reduced rates. Most others still full retail.

Pick your state to see your payback.

Recommended system size—

Net system cost (after credit + rebate)—

Annual production (Year 1)—

Year 1 savings—

25-year net savings—

25-year ROI—

Cumulative savings vs. system cost

Cumulative savings System cost (break-even) Payback year

How this calculator works

Most "solar calculators" online ask you for system size, sun hours, and installed cost — numbers you can't possibly know unless you've already gotten quotes. This one only asks for your state and monthly bill. Everything else comes from public data.

Where the numbers come from

Electricity rate: EIA residential average rate for your state (2024-2025 data, refreshed annually)

Sun hours: NREL state average peak-sun-hours (the gold standard for solar production estimation)

System size: We auto-size to cover ~100% of your annual usage (your bill ÷ rate × 12, then divided by sun hours × 365 × 0.80 efficiency)

Installed cost: SEIA/Wood Mackenzie state-by-state averages (CA ~$3.85/W, AZ ~$2.70/W, NY ~$3.55/W, etc. — varies widely by local labor + permit costs)

Net metering policy: Encoded per state as of 2026 — full retail (most states), reduced/avoided-cost (CA NEM 3.0, HI, NV, AZ, and several others), or no NEM. Affects how much your excess production is worth.

Electricity inflation: EIA 20-year average of ~3.5% annual rate growth

Federal credit: 30% per the Residential Clean Energy Credit (Inflation Reduction Act, through 2032)

The formula

Annual production = system size (kW) × daily sun hours × 365 × 0.80 (real-world efficiency factor)

Year 1 savings = annual production × your electricity rate (capped by net-metering policy)

Year N savings = Year 1 savings × (1 + inflation rate)^N-1

Net system cost = (system size × 1000 × $/watt) − federal tax credit − state rebate

Payback year = the first year cumulative savings ≥ net system cost

What we deliberately don't do

We don't collect your address, phone number, or email. We don't sell your data to installer lead-gen networks. We don't have a "get free quotes" button hidden behind a calculation. You get the math and the assumptions; what you do with it is up to you.

FAQ

How long does it take for solar panels to pay for themselves?

Most US residential systems pay back in 7-12 years. High-rate states like California, Hawaii, and Massachusetts often see payback under 8 years. Lower-rate states like Louisiana and Washington can stretch to 12-15 years.

Does the federal tax credit make a big difference?

Yes — significantly. The 30% Residential Clean Energy Credit can shave 2-4 years off payback on a typical $25,000 system. The credit was extended through 2032 by the Inflation Reduction Act.

How do you estimate my system size and cost?

We use your monthly bill to estimate annual kWh usage (bill divided by your state's average electricity rate). Then we size a system big enough to offset that usage given your state's sun hours. Installed cost defaults to $3.20/watt — the US national average. You can override any of these in the Advanced inputs.

What if my actual electricity rate is different from the state average?

Open the "Adjust assumptions" panel and override the rate field. Your latest electric bill should show the rate (often listed as "Energy Charge" or "$ per kWh"). California's state average is $0.32/kWh but PG&E Tier 3 can exceed $0.55/kWh — using your actual rate makes the calculation much more accurate.

Why a 0.80 efficiency factor?

Real-world solar systems produce about 75-85% of their theoretical nameplate rating. Losses come from panel temperature derating, inverter conversion (~95% efficient), DC-AC losses, wire losses, soiling, occasional shading, and ~0.5%/yr panel degradation. NREL's PVWatts model uses similar derating; 0.80 is a sensible residential default.