Size a system, compare how you pay, and see the long view.
A transparent planning estimate, built around your assumptions.
Use a recent utility bill and an itemized quote when available.
System size is rounded to whole panels and limited by entered roof area. Cost recovery uses annual cash flows; no month-level payback precision is implied.
Annual energy balance, not an hourly or seasonal simulation. Annual generation can exceed demand while grid imports remain, because production and household usage occur at different times.
Backup requires compatible equipment and a suitable installation. Runtime excludes recharging, starting surges and changing loads. Storage does not automatically raise the modeled self-use percentage.
Loan figures describe the alternative loan scenario even when cash is selected. Prices come from your inputs, not local installer quotes. Confirm fees and repayment terms against your proposal.
Ask an installer to confirm production, usable roof area, equipment, warranties, utility rules and the full cash or financed price. We do not show an invented count of available installers or a guaranteed local price.
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Compare cash flow, financing, and the assumptions that can change the outcome.
Savings minus upfront, operating, replacement, and loan costs. The zero line shows cost recovery.
| Year | Production (kWh) | Utility savings | Upkeep + replacements | Loan payments | Net cash flow | Cumulative |
|---|
Same plan, with 15% less annual production and 15% higher solar installation cost. Battery price stays unchanged.
This is one sensitivity test, not a confidence interval. Weather, export rules, financing, and repairs can change together.
This tool is built for comparing assumptions. It does not inspect your roof, query your utility, or promise an installation price or return.
Our research & disclosure standards →Editorial contact: Aizaz Shahid, Founding Editor
Model version 1.1 · October 2, 2026
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Annual home use is your entered kWh × 12, or (monthly bill − fixed charges) ÷ energy rate × 12. Optional EV use adds miles ÷ mi/kWh ÷ charging efficiency. Target kW = annual demand × target percentage ÷ annual yield. We round up to whole panels, then apply your panel-area limit.
Annual generation = installed DC kW × entered AC yield. Self-used energy is capped at annual demand. The rest is exported. Imports = demand − self-use. Export credits are capped at imported-energy charges. Fixed charges remain payable. This annual approximation excludes time-of-use tariffs, demand charges, seasonal credit rollover, cash export payouts, and hourly battery dispatch.
Solar cost = DC watts × entered installed $/W. Battery cost is added separately; confirmed upfront rebates reduce that total. Each year accounts for utility savings, maintenance, entered replacement costs, and loan payments. Maintenance grows 2% annually. Production declines at your rate; retail energy prices grow at your rate. Fixed charges, export rates, and future replacement amounts stay constant.
The chart starts with the cash purchase or loan down payment at year zero. Cash recovery is the first end-of-year cumulative balance that stays nonnegative through year 25. A zero-down loan is not described as instant payback. NPV discounts future net cash flows at your chosen rate. Nominal net outcome is not inflation-adjusted. No resale value, carbon income, automatic tax credit, or other unentered benefit is added.
Available stored energy = capacity × available energy fraction. Runtime = available kWh ÷ constant critical load in kW, provided the load fits the entered continuous output limit. This is not an appliance compatibility check. Starting surges, battery aging, recharge, and changing loads are excluded. Battery addition changes cost and replacement assumptions; it does not silently increase the self-use percentage.
All defaults are editable illustrative assumptions, not verified local tariffs, market quotes, or a weather simulation. Use a site-specific production estimate and itemized installer proposal. DOE’s homeowner solar guide explains equipment, planning, and utility questions. DOE’s resilience guidance explains backup requirements. The IRS credit page governs federal eligibility; these sources do not endorse this site.
The calculator itself does not send your inputs to a server. “Save on this device” stores the scenario in this browser; Reset removes that saved scenario. CSV and print exports are generated locally. Quote requests use a separate form governed by our privacy policy. AI assisted implementation; this is not proof of accuracy. See our research and disclosure standards.