Updated October 22, 2026
This solar quote calculator sizes and prices a home system the way an installer quotes it: yearly usage and the share you want to cover, production per kW for the site, panels rounded to whole modules, price per watt, any incentives you enter yourself, and the homeowner's electricity rate with escalation and panel degradation. You get the system size and price, the net cost, the payback in years and 25-year savings for the homeowner, and your gross margin as the installer.
Quick answer: System kW = yearly kWh × share to cover ÷ kWh per kW per year, rounded up to whole panels. Price = system watts × price per watt. Net cost = price − incentives you enter. Payback = the year cumulative savings pass the net cost, with savings = production × electricity rate, rising with the rate and falling with degradation.
An estimate from the numbers you entered, not a market price. Put in your own costs for a number you can stand behind.
Home service businesses answer only about half their calls (Invoca, July 2026), and owners spend about 11 to 16 hours/week on admin. Pricing is the easy part; the money leaks out in the calls you can't take, the quotes nobody chases and the invoices that sit unpaid. Unmanually is a 24/7 AI Office Manager for solar installers that you run by voice from your phone:
Sources: Invoca, July 2026 (52% of home-service calls answered by a person, 60M+ calls); admin hours: Time etc / Censuswide 2023 and Amex SME Barometer 2026.
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system kW needed = yearly kWh × share to cover ÷ kWh per kW per yearpanels = kW needed × 1,000 ÷ panel watts, rounded up; system kW = panels × panel watts ÷ 1,000price = system watts × price per watt; net cost = price − federal credit % entered − other incentives enteredfirst-year savings = system kW × kWh per kW × electricity rateeach later year = previous year × (1 + price increase) × (1 − degradation)payback = years until cumulative savings reach the net cost; gross margin = (price − cost per watt × watts) ÷ price
These are assumptions for illustration, not market prices, and no incentives are included. Enter only incentives you have confirmed.
A home using 10,800 kWh a year, covering 90%, at a site producing 1,300 kWh per kW per year. 420 W panels, $3.20 a watt to the customer, $2.30 a watt installed cost, electricity at $0.16 a kWh rising 3% a year, 0.5% panel degradation a year, federal credit and other incentives left at 0.
The home needs 10,800 × 90% = 9,720 kWh, or 9,720 ÷ 1,300 = 7.48 kW. That rounds up to 18 panels, 7.56 kW. The price is 7,560 W × $3.20 = $24,192. The system makes 9,828 kWh in year one, saving $1,572. With rates rising and output slowly falling, savings pass the cost after about 13.2 years and add up to $53,608 over 25 years, $29,416 net. Your gross profit is $24,192 − 7,560 × $2.30 = $6,804, a 28.1% margin.
A confirmed $2,000 state rebate would shorten payback to about 12.2 years. At a $0.25 rate with no increases, payback is about 10.1 years.
Start with a year of usage, decide how much to cover, and divide by the production a kW will make on that roof. Then round to whole panels, because that is what goes on the roof. Production depends on the site: direction, tilt, shading and climate all move it, so use a production model for the address rather than a regional average.
Two quotes for different system sizes can't be compared on the total. Price per watt can. Show it on every quote, and the net cost per watt after any incentives, so the homeowner can compare like with like.
The federal residential clean energy credit is a good example. The IRS says the credit is not available for any property placed in service after December 31, 2025 (IRS). That is why this calculator defaults every incentive to 0. State, local and utility programs open and close too. Confirm each one for the customer and the system before you put it in a quote; this is not tax advice.
The electricity rate, how the utility credits exported power and any fixed charges all change what solar saves. Use the customer's real rate from the bill, check the utility's current export rules, and be conservative on the rate increase you assume.
A quote that looks great for the customer but leaves no margin for the installer helps nobody when a warranty call comes. Keep your installed cost per watt current, including sales and permitting time, and look at gross margin on every quote.
Batteries, main panel upgrades and roof replacements change both the price and the payback. Quote them as separate lines so the customer sees what each adds, and run the calculator with and without them.
Homeowners asking about solar call several installers and meet with the one who calls back first. Unmanually is an AI Office Manager that works 24/7 and that you run by voice: the AI Office Manager answers, asks the monthly bill, roof age, shade and ownership, books the site visit or consultation and texts the confirmation, follows up on the proposal, then sends invoices and chases milestone payments. See what Unmanually does for solar installers, or get a free website that calls every new lead back in about a minute.
What the AI Office Manager does for solar installers, from inquiries to milestone invoices.
Why the first installer to call back gets the meeting.
Lead sources for solar installers.
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Divide the yearly kWh you want to cover by the kWh one kW of panels will produce at that site per year, then round up to whole panels. In the example, 9,720 kWh ÷ 1,300 = 7.48 kW, which is 18 panels of 420 W, or 7.56 kW.
Add up the yearly electricity savings, rising with the rate and falling with panel degradation, until they pass the net cost. The calculator gives the payback in years and 25-year savings.
The IRS says the residential clean energy credit is not available for any property placed in service after December 31, 2025. The calculator's federal credit field defaults to 0; check current IRS rules for any customer and system.
It depends on the market, equipment and installer. Use your own cost per watt and target margin; the calculator shows both the customer's price per watt and your gross margin.
Only ones you have confirmed are open and apply to that customer. The calculator leaves them at 0 until you enter them and warns you to confirm them.
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