Rooftop solar · Bill and quote comparison
Solar Savings Calculator
Start with an average monthly electric bill, the installed cash price, and the bill-reduction percentage shown in a solar proposal. Open the detailed model only when you have annual production, retail-rate, self-consumption, and export-credit data.
Quick estimate
Start with your electric bill and solar quote
Modeled 25-year net savings
$27,545Modeled cumulative payback in year 13The quick estimate applies the proposal's expected bill reduction to your entered bill. Fixed utility charges, future rate plans, export rules, financing, and proposal assumptions can materially change the result.
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How this calculator works
The quick estimate avoids requiring a utility rate or annual kWh total. It multiplies the average annual bill by the proposal's expected bill-reduction percentage, then projects that bill value against the entered cash price.
Detailed production modeling is optional
When the source numbers are available, annual production is taken directly from NREL PVWatts or the installer proposal. Solar used by the home avoids entered retail purchases, while remaining production is valued at the entered export credit.
Proposal bill reduction is not system production
Use a stated utility-bill reduction or offset after fixed charges and export rules—not the panel production percentage. Net-metering rules, time-of-use rates, minimum bills, rollover, and annual true-ups can make the proposal estimate differ from actual bills.
The 2026 federal residential default is zero
The federal Section 25D Residential Clean Energy Credit is not allowed for expenditures after December 31, 2025 under current law. Therefore this 2026 calculator defaults the federal incentive to 0%, not the former 30%. Enter only a different project-date or incentive assumption you have verified.
Payback and NPV are different views
Simple payback divides net cost by first-year savings. Modeled payback allows production degradation and electricity-price changes. Net present value additionally discounts future savings, which makes distant savings worth less today.
Roof replacement timing, shading, equipment degradation, inverter replacement, financing charges, insurance, utility rule changes, solar renewable energy credits, and production guarantees can dominate a quote comparison.
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Worked example
Suppose the average electric bill is $200 per month and a $24,000 cash proposal estimates a 75% utility-bill reduction. The quick estimate starts with a $2,400 current annual bill and $1,800 of first-year avoided bill before the entered maintenance allowance.
The 2026 example applies no federal residential credit unless the user enters a verified amount. Detailed mode can replace the proposal-level estimate with PVWatts production, the share used by the home, retail rate, and export compensation.
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Questions people ask
What if I only know my monthly electric bill?
Use the quick estimate. Average twelve months of bills, enter the installed cash price, and copy the proposal's estimated utility-bill reduction. You do not need a per-kWh rate unless you switch to detailed mode.
How do I estimate solar production?
For detailed mode, use NREL PVWatts with the property location, system size, tilt, azimuth, array type, and losses, then enter its annual kWh result.
Is there a federal solar tax credit in 2026?
Under current law, the Section 25D residential clean energy credit is not available for expenditures after December 31, 2025. Confirm project timing and later legal changes with the IRS or a qualified adviser.
What is solar self-consumption?
It is the portion of solar generation used by the home rather than exported. Batteries, load timing, system size, and household usage pattern affect it.
Why is my utility estimate different?
Utilities may use time-of-use prices, nonbypassable charges, fixed fees, different export prices, monthly rollover, or annual settlement. This annual model is deliberately simplified.
Does the calculator include a solar loan?
No. Enter the cash-equivalent installed price. Financing fees and interest should be modeled separately because dealer fees can be embedded in the quoted system price.
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Sources and model basis
Published rules and formulas are linked below. Values supplied by the visitor remain scenario inputs, not factual claims.
- NREL PVWatts CalculatorLocation-specific grid-connected PV production estimates
- NREL PVWatts V8 documentationCurrent model inputs, weather data, and output definitions
- Department of Energy: Will I save money with solar?Production, consumption, utility compensation, and payback factors
- IRS: Energy credit modification FAQsSection 25D termination for expenditures after December 31, 2025