Skip to main content
Tool Belt Calc

Electrical

Solar Payback Calculator

Payback period and 25-year savings on a solar system.

Your measurementsEvery assumption editable01

Residential systems commonly run $2.50–$3.50 per watt before incentives.

Federal, state and utility incentives combined, as a share of gross cost.

From the panel calculator, or your installer's estimate.

How fast you expect electricity prices to climb. 2–4% is a common assumption.

Modules lose output slowly. 0.5% a year is a typical warranty figure.

PaybackCalculated live02

Result

8.8yr payback

$16240 net cost — $57274 saved over 25 years

Gross system cost8 kW at $2.9/W
$23200
Incentives30%
−$6960
Net cost
$16240
First-year saving10500 kWh at 16¢
$1680
Simple payback
8.77 years
25-year savingsassuming 3% rate rises and 0.5% degradation
$57274
Net 25-year gain
$41034

This walks the cash flows year by year rather than dividing cost by first-year saving, because two things change over time in opposite directions: panels produce slightly less each year while electricity gets more expensive. Rate escalation usually outruns degradation, which shortens payback against the naive figure.

The rate escalation assumption does most of the work in the 25-year number and nobody knows it. At 2% the lifetime figure is far lower than at 5%, so treat the long-run total as a scenario rather than a forecast — the payback year is the more defensible output.

Financing, maintenance, inverter replacement around year twelve to fifteen, and any net-metering rules that credit exports below retail are all excluded. Net metering in particular varies enormously by utility and can change the economics substantially.

This walks the cash flows year by year rather than dividing cost by first-year savings, because two things change in opposite directions: panels produce slightly less each year while electricity gets more expensive.

Why use this tool?What it does differently03

Why use this tool?

Year-by-year cash flow

Rate escalation and panel degradation modelled separately over 25 years, not averaged.

Interpolated payback

The break-even point within a year, not rounded to a whole one.

Incentives separated

Gross cost, incentive value and net cost all shown.

Honest about assumptions

Rate escalation does most of the work in the 25-year figure and nobody knows it.

How this worksThe method04

How this solar payback calculator works

Each year's saving is that year's production times that year's electricity rate. Production falls by the degradation percentage annually while the rate rises by the escalation percentage, so the two are tracked separately rather than netted into one assumption.

Payback is the point at which cumulative savings cross the net cost, interpolated within the year rather than rounded. Rate escalation usually outruns degradation, which shortens payback against the naive cost-divided-by-first-year-saving figure.

The 25-year total is far more sensitive to the escalation assumption than to anything else. Treat the payback year as the defensible output and the lifetime figure as a scenario.

How to use itStep by step05

How to use it

  1. Step 1: Enter system size and cost

    Installed cost per watt before incentives. Residential commonly runs $2.50–$3.50.

  2. Step 2: Add incentives

    Federal, state and utility combined, as a share of gross cost.

  3. Step 3: Enter production

    From the panel calculator or your installer's estimate.

  4. Step 4: Set escalation conservatively

    It drives the lifetime figure more than anything. 2–3% is defensible; higher is optimistic.

Example usageWorked figures06

Example usage

A typical 8 kW system
$23,200 gross at $2.90/W, less 30% incentives, is $16,240 net. Producing 10,500 kWh at 16¢ saves $1,680 in year one and pays back in 8.77 years.
Over 25 years
The same system saves about $57,274 with 3% rate rises and 0.5% degradation — a net gain of roughly $41,034 after the install cost.
A cheaper rate
At 10¢ rather than 16¢ the payback stretches past fourteen years. Your electricity rate is the single biggest determinant of whether solar makes sense.
Frequently asked questionsCommon questions07

Frequently asked questions

How long does solar take to pay back?

Commonly seven to twelve years in the US, depending heavily on your electricity rate, local sun and available incentives. An 8 kW system at 16¢ per kWh typically lands near nine years.

Do solar panels lose output over time?

Slowly. Around 0.5% a year is a typical warranty figure, so a panel still produces roughly 88% of its original output after 25 years.

What rate escalation should I assume?

Two to three per cent is defensible. It has an outsized effect on the lifetime figure, so a conservative assumption makes the result far more trustworthy.

Does this include financing?

No. It compares a cash purchase against doing nothing. Loans, leases and power purchase agreements all change the economics substantially and differ enormously between offers.

What about net metering?

Not modelled, and it matters. Utilities that credit exports below retail rate materially lengthen payback, and those rules have been changing in several states.

Related toolsElsewhere on the site08

Browse every tool in Electrical Calculators.