Solar Savings & Payback Calculator

Your solar savings estimate

Net system cost

First-year electricity value, before maintenance

First-year savings, after maintenance

Average monthly savings

Effective first-year electricity value

Projected first break-even

Electricity value is avoided electricity expense plus export value, not profit. Net benefit subtracts maintenance and net system cost. The first break-even is the first year-end crossing; later costs or reduced production can reverse it. Monthly savings are an annual average, not a seasonal forecast.

How it works

Net system cost = installation cost − your incentives. Effective value per kWh = full-retail percentage × retail rate + remaining percentage × export rate. First-year electricity value = annual production × effective value. First-year savings = electricity value − annual maintenance. Simple payback = net system cost ÷ first-year savings.

With zero rate increase and degradation, each future year repeats year-one savings. At 10, 20 and 25 years, net benefit = cumulative savings after maintenance − net system cost. With optional assumptions, year y production = first-year production × (1 − degradation)^(y − 1), and retail rate = current rate × (1 + increase)^(y − 1). Export rate and annual maintenance stay fixed. We sum each year’s electricity value minus maintenance and show the first year-end that recovers net cost.

Assumptions and useful information

This models a cash purchase with incentives treated as upfront cost reductions. There are no automatically assumed incentives, financing terms, tax rules, utility policies or price forecasts. Incentive eligibility and payment timing must be checked separately.

Full-retail value can come from self-consumption or utility credits. Check your actual tariff, time-of-use prices, export caps and credit expiration. Annual usage alone cannot show when generation offsets purchases, so this calculator does not infer the percentage or cap results to your bill. Fixed charges and demand charges may remain payable.

The 25-year horizon is a scenario, not a warranty. Flat projections use entered rates without inflation or discounting. Optional projections are nominal, undiscounted cash flows. Financing, insurance changes, taxes on exports, roof work, inverter/battery replacement, resale value and opportunity cost are excluded unless you account for a cost in your inputs. Zero degradation and maintenance are transparent simplifications, not realistic guarantees.

Background: DOE solar savings guidance and DOE homeowner solar guide. Check your own quote and utility contract; this tool does not determine eligibility.