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Solar Calculator

U.S. only tools

Two numbers decide whether a rooftop system is worth buying: what it costs to make a kilowatt-hour with it, and what the utility charges for one. This page puts those two side by side. The system’s own figure is the price you pay, divided by every kilowatt-hour it will ever produce, and it does not move when the utility raises its prices — which is most of the argument for solar in one line.

Solar Calculator - Danfio

https://danfio.com/tools/solar-calculator/ - printed from this page

Currency: USD ($) - display only, nothing was converted

The rated output on the quote.

$

Per watt, before incentives. If you only have the total, divide it by the system size in watts.

The 25D credit is 30 percent for property placed in service in 2022 through 2032, 26 percent in 2033 and 22 percent in 2034. For a 2026 installation that is 30 percent.

$

Money taken off the price at the point of sale.

From your installer’s production model for your roof, which is the figure that decides everything below.

EIA’s average residential price for June 2026 is 18.34 cents; the number off your own bill is better.

A scenario, not a forecast. Nothing on this page predicts the price of power - 0 percent is the cautious case.

Panels make slightly less each year. Your warranty states what the maker guarantees.

$

An inverter is usually the one large replacement, around the middle of a system’s life.

The usual planning figure is 25, which is also what warranties tend to cover.

Results update as you type. Nothing leaves your device.

Currency symbol

Symbol only - nothing is converted and no exchange rate is used. Figures quoted in the explanation text stay as the sources publish them.

The system’s own cost per kWh

6.4 cents

Against 18.34 cents a kilowatt-hour from the grid. The system costs $16,800 after incentives and would make about 263,828 kWh over 25 years.

Net cost after incentives
$16,800 $24,000 less incentives
First-year value
$2,054 less $150 of running costs
Pays for itself in
9 years
Left over 25 years
$49,477 value less running costs and the net price

The purchase

Gross installed cost
$24,000
Federal credit entered
$7,200 30% of the price
Rebates
$0
First-year production
11,200 kWh 1,400 kWh per kW installed

The system over the years

YearProductionUtility priceValueRunning costsRunning total
111,200 kWh18.34¢$2,054$150-$14,896
211,144 kWh18.89¢$2,105$150-$12,941
311,088 kWh19.46¢$2,157$150-$10,933
411,033 kWh20.04¢$2,211$150-$8,872
510,978 kWh20.64¢$2,266$150-$6,756
610,923 kWh21.26¢$2,322$150-$4,584
710,868 kWh21.9¢$2,380$150-$2,354
810,814 kWh22.56¢$2,439$150-$65
910,760 kWh23.23¢$2,500$150$2,285
1010,706 kWh23.93¢$2,562$150$4,697
1110,652 kWh24.65¢$2,625$150$7,172
1210,599 kWh25.39¢$2,691$150$9,713
1310,546 kWh26.15¢$2,758$150$12,321
1410,493 kWh26.93¢$2,826$150$14,997
1510,441 kWh27.74¢$2,896$150$17,743
1610,389 kWh28.57¢$2,968$150$20,562
1710,337 kWh29.43¢$3,042$150$23,454
1810,285 kWh30.31¢$3,118$150$26,422
1910,234 kWh31.22¢$3,195$150$29,467
2010,183 kWh32.16¢$3,275$150$32,592
2110,132 kWh33.12¢$3,356$150$35,798
2210,081 kWh34.12¢$3,439$150$39,087
2310,031 kWh35.14¢$3,525$150$42,462
249,980 kWh36.2¢$3,612$150$45,925
259,931 kWh37.28¢$3,702$150$49,477

Production falls by 0.5% a year and the utility price is assumed to rise by 3% a year. The running total starts below zero, at minus the net price, and turns positive in the year the system has paid for itself.

Pays for itself at three utility-price paths

Utility price risesPays for itself in
0% a year10 years
3% a year9 years
6% a year8 years

The same system, the same production, three assumptions about the price of power. Nothing here predicts that price: the table exists so the range can be seen rather than one number being believed.

You entered a federal credit of 30%. The residential clean energy credit is 30 percent for property placed in service in 2022 through 2032, 26 percent in 2033 and 22 percent in 2034, and is not available after 2034, so the default matches the current rate and lower numbers are the cautious case. System owners who lease or buy power through a third party are under different rules again, and a home used partly for business is a third set.
What decides this answer and is not in the numbers you typed: how your utility credits what the panels send to the grid. This page assumes every kilowatt-hour offsets one you would otherwise have bought at the retail rate, which is what net metering means, and which a growing number of utilities no longer offer in full - if exports are credited at a wholesale rate instead, the value of the oversized part of a system falls a long way. Also outside the arithmetic: roof condition and any needed replacement, permits and inspection fees, HOA approval, insurance changes, tax on a rebate, and a battery, which is a separate purchase with its own math. There is no discounting either: the running total is the arithmetic of the money, not a rate of return, because a rate of return would need a discount rate the page did not ask for.

The page is also honest about the federal residential clean energy credit. For a system placed in service in 2026 it is 30 percent of qualifying costs - the same rate that applies to property placed in service in 2022 through 2032, before it steps down to 26 percent in 2033 and 22 percent in 2034 and expires after that. The credit field starts at that current 30 percent, because that is the number on most 2026 quotes, and you can change it if your situation differs.

About this solar calculator

Seldom does a rooftop array pay back as quickly as the sales call implies, and the honest way to judge one is to price the electricity it makes against what the utility charges. This page does that in cents per kilowatt-hour and in a payback period, so the two can be compared with the figure on your bill.

Money spent against kilowatt-hours produced is a comparison a visitor can check, so the page carries a running total rather than dressing the result up as a rate of return. It runs client-side in your browser, and the quote, the production figure and your utility rate all stay on your own machine.

Treat the cost per kilowatt-hour and the payback as estimates from the numbers you enter, not a rate of return or a forecast of utility prices. Export compensation, time-of-use rates, roof repairs, permits, batteries and inverter replacement as a dated cost are all outside the model. Enter the production figure from your own roof rather than a national average before you judge the system.

How this solar calculator works

Cents a kilowatt-hour, not just a payback period

Take everything the system costs — the installed price, less the federal credit and any rebate — and divide it by the kilowatt-hours it will produce over the years you are counting. The result is what your own electricity costs you. Compare it with the price on your utility bill. On the sample system on this page, 8 kW at $3 a watt making 1,400 kWh per kilowatt a year, that is about 6 cents a kilowatt-hour against the 18.34 cents EIA recorded as the U.S. residential average for June 2026.

A payback period says the same thing in different units, so the page shows both. What it does not do is pretend to be a rate of return: no discount rate is applied, because that would need an assumption about the next twenty-five years that nobody has. The running total is money — what the system has cost and what it has saved — and it is the honest version of the arithmetic the visitor can check.

What the federal credit is worth

The residential clean energy credit is 30 percent of the cost of qualifying property placed in service from 2022 through 2032, falling to 26 percent in 2033 and 22 percent in 2034 before it expires. That one line moves the arithmetic: on the sample system the credit is worth $7,200 of the $24,000 price, which is why a field that ignores it makes the same system look about a third more expensive than the law makes it today.

Two neighboring rules are outside this page and worth naming so nobody assumes they do not exist: systems that are leased or bought through a power purchase agreement are owned by a third party and fall under different rules from a homeowner purchase, and a home used partly for business is a third case again. If either applies, the inputs on this page are not the whole calculation.

The things that decide whether it pays off

Production is the first: where you live, which way the roof faces, how steep it is and how much shade falls on it. That is why the page asks for the figure from your installer’s model rather than printing a national one, and why PVWatts is worth running yourself — it is free, and it is the same kind of model the quotes are built on.

The second is how your utility credits what you send to the grid. This page assumes every kilowatt-hour produced offsets one you would have bought at the retail rate, which is what full net metering means. Utilities that credit exports at a wholesale rate, or that charge a fixed connection fee per month to solar customers, change the answer for the part of production you do not use yourself. The third is how long you stay: a system pays back over about a decade and then keeps producing, so moving in year four turns a twenty-five-year calculation into a four-year one.

Degradation, maintenance and the inverter fund

Production is not constant: panels lose a small share of output every year as they age, which is what the degradation field enters, and the running-costs field covers the flat annual spend on cleaning, insurance and the inverter replacement that lands once in the life of the system.

Neither number moves the comparison much in the early years, which is why a quote can leave both out; across twenty-five years they help decide whether the payback year holds. A flat annual figure is an approximation on purpose, not a forecast of what a repair will cost in year thirteen. An estimate, not a return, and not tax advice.

Worked examples

Each example below was run through the calculator on this page when the site was built, so the numbers match what you see when you enter the same inputs.

8 kW at $3 a watt, no federal credit

System size: 8 kW · Installed cost: $3.00 · Federal residential credit: 0% · State, utility or installer rebate: $0.00 · Production a year: 1,400 kWh per kW · What the utility charges: 18.34 cents a kWh · Utility price rises: 3% · Output lost a year: 0.5% · Cleaning, insurance and the inverter fund: $150.00 · Years to count: 25 years

The system’s own cost per kWh

9.1 cents

Against 18.34 cents a kilowatt-hour from the grid. The system costs $24,000 after incentives and would make about 263,828 kWh over 25 years.

Net cost after incentives: $24,000 · First-year value: $2,054 · Pays for itself in: 12 years · Left over 25 years: $42,277

The same $24,000 system without any credit: about 9 cents a kilowatt-hour over twenty-five years and a payback in the teens, which is the cautious case. Entering the current 30 percent credit shortens both.

The same system with the current 30 percent credit

System size: 8 kW · Installed cost: $3.00 · Federal residential credit: 30% · State, utility or installer rebate: $0.00 · Production a year: 1,400 kWh per kW · What the utility charges: 18.34 cents a kWh · Utility price rises: 3% · Output lost a year: 0.5% · Cleaning, insurance and the inverter fund: $150.00 · Years to count: 25 years

The system’s own cost per kWh

6.4 cents

Against 18.34 cents a kilowatt-hour from the grid. The system costs $16,800 after incentives and would make about 263,828 kWh over 25 years.

Net cost after incentives: $16,800 · First-year value: $2,054 · Pays for itself in: 9 years · Left over 25 years: $49,477

The current 30 percent credit takes $7,200 off the $24,000 price and roughly three years off the payback. It applies to property placed in service from 2022 through 2032; the rate steps down to 26 percent in 2033 and 22 percent in 2034.

A high-price market: 30 cents a kilowatt-hour

System size: 8 kW · Installed cost: $3.50 · Federal residential credit: 0% · State, utility or installer rebate: $0.00 · Production a year: 1,250 kWh per kW · What the utility charges: 30 cents a kWh · Utility price rises: 3% · Output lost a year: 0.5% · Cleaning, insurance and the inverter fund: $150.00 · Years to count: 25 years

The system’s own cost per kWh

11.9 cents

Against 30 cents a kilowatt-hour from the grid. The system costs $28,000 after incentives and would make about 235,559 kWh over 25 years.

Net cost after incentives: $28,000 · First-year value: $3,000 · Pays for itself in: 9 years · Left over 25 years: $70,524

Less production and a higher price per watt, but the utility price is the number that decides: at 30 cents a kilowatt-hour the same purchase pays back far sooner.

The 30 percent credit plus a $1,500 state rebate

System size: 8 kW · Installed cost: $3.00 · Federal residential credit: 30% · State, utility or installer rebate: $1,500.00 · Production a year: 1,400 kWh per kW · What the utility charges: 18.34 cents a kWh · Utility price rises: 3% · Output lost a year: 0.5% · Cleaning, insurance and the inverter fund: $150.00 · Years to count: 25 years

The system’s own cost per kWh

5.8 cents

Against 18.34 cents a kilowatt-hour from the grid. The system costs $15,300 after incentives and would make about 263,828 kWh over 25 years.

Net cost after incentives: $15,300 · First-year value: $2,054 · Pays for itself in: 8 years · Left over 25 years: $50,977

The current 30 percent credit takes $7,200 off the price and the $1,500 rebate takes more, so the net cost is $15,300: 5.8 cents a kilowatt-hour against the grid rate of 18.34 cents, paying for itself in eight years and leaving $50,977 over the term.

Frequently asked questions

Is the 30 percent federal solar credit still available?

Yes for a new homeowner installation. The IRS page describing the Residential Clean Energy Credit says it is 30 percent of the cost of qualified property placed in service from 2022 through 2032, 26 percent in 2033 and 22 percent in 2034, and is not available for any property placed in service after 2034. So a 2026 quote can honestly include the 30 percent credit, and this page defaults to it. The rate steps down as the law runs out, so check which year your system will be placed in service. Leases and power purchase agreements are third-party owned and follow different rules, and a home used partly for business is another case — check the current rules for whichever applies, because this page models a homeowner purchase only.

How long does a solar system take to pay for itself?

It depends on four things, all of which are in the fields above: what it cost per watt, how much it produces, what the utility charges now, and how fast that price rises. On the sample system — 8 kW at $3 a watt in a market paying 18.34 cents a kilowatt-hour — at the current 30 percent credit it is about 9 years, and in the teens of years with no credit at all. The page prints the payback at 0, 3 and 6 percent utility-price growth so the sensitivity is visible rather than buried in a single figure.

What is net metering, and why does it change the answer?

Net metering means the utility credits exported kilowatt-hours at the same retail price you would pay to buy them, so every hour of production is worth the full retail rate. That is the assumption this page makes, and it is the assumption a growing number of utilities no longer grant: some credit exports at a wholesale rate, and some charge solar customers a fixed monthly fee. Where exports are worth less, only the part of production you use yourself is worth the retail price, and the arithmetic of an oversized system gets worse. Ask your utility what it credits, and how, before signing anything.

How much does solar cost?

This page takes the price from your quote rather than printing a national average, for the same reason it takes production from your installer’s model: installed prices vary with the market, the equipment, the roof, the permitting and the installer, and the number that matters is the one on the paper in front of you. What the page then does is convert that price into cents per kilowatt-hour, the only form in which it can be compared with a utility bill.

Does the price include a battery?

No, and the page does not model one. A battery is a separate purchase with its own justification — backup power, or avoiding a utility that pays little for exports — and it rarely pays for itself on economics alone. If a quote bundles panels and a battery, split the two prices and run the panels here on their own, or the working costs will be spread over a system that is doing two different jobs.

What happens when the inverter fails?

An inverter usually needs replacing once in a system’s life, somewhere around the middle of it, and that is the lumpiest cost in the whole calculation. The page carries a flat annual figure for cleaning, insurance and putting money aside for that replacement; a flat figure is honest about being an approximation rather than a forecast. If your quote includes an extended inverter warranty, that annual figure can be lower.

Does solar add value to a house?

Often, but not in a way this page will put a number on. What the arithmetic can say is what the system produces and what that production is worth at today’s utility price — a defensible thing to show a buyer, because it is a calculation rather than a claim about the market. How much a particular buyer pays for it, and whether an appraiser credits it at all, is not something arithmetic can settle.

What does the site do with the numbers I put on this page?

The quote, the production figure and your utility rate never leave the page itself: the arithmetic runs locally in your browser, nothing is uploaded and there is no endpoint that could receive it. A test in this site’s own suite fails our checks if a calculator page ever reaches the network, so the local-only behavior is verified when the page was prepared rather than merely asserted.

Assumptions and sources

  • EIA, Electric Power Monthly, Table 5.6.A — average price of electricity to ultimate customers, by end-use sector and state. The U.S. total for residential customers was 18.34 cents a kilowatt-hour in June 2026, against 17.47 cents in June 2025 (released 26 August 2026). The page uses it as the default utility price and prints the month beside it, because the figure is republished monthly.
  • IRS, Residential Clean Energy Credit — the credit is 30 percent of the cost of new qualified clean energy property placed in service from 2022 through 2032, 26 percent in 2033 and 22 percent in 2034, and is not available for property placed in service after 2034. The same page notes that the credit is nonrefundable, that unused credit can be carried forward, and that the property must be installed — not merely bought — in the year it is claimed.
  • Production is the visitor’s own figure, from the installer’s model for that roof. It depends on location, tilt, orientation and shading, which is why no national average is printed; NREL’s PVWatts is the free tool that produces the same kind of estimate, and it is worth running independently of any quote.
  • Not modelled here: export compensation and net-metering rules, time-of-use rates, fixed monthly charges for solar customers, roof repairs or replacement, permits and inspection fees, HOA approval, insurance changes, tax on a rebate, batteries, inverter replacement as a dated cost, and any discount rate. The comparison is a simple one — money spent against kilowatt-hours produced — and the page says so rather than dressing it up as a rate of return.

Last reviewed 2026-09-23. Not investment or insurance advice; quotes come from a licensed provider. Read the full disclaimer.

Where a figure on this page comes from an official agency — HUD, IRS, FICO or a state body — the site keeps a dated snapshot of the source page in its sources library, and a scheduled job re-checks that snapshot, so the number can be traced back to the document it came from.

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