What affects the price of home solar

System size, equipment, roof, labor, batteries, financing and location: why two quotes for the same house can differ, and how to ask for numbers you can compare.

Two installers can quote very different prices for the same roof, and both can be reasonable. The gap usually comes from what is included, how big the system is, and how the company runs its business. This guide walks through the main drivers so you can read both the numbers on this site and the quotes in your inbox. It is general information, not advice about your home.

System size and fixed costs

Many costs are paid once per job, whatever the size: the site visit, the design, permit paperwork, the utility interconnection application, inspection, and the crew's travel. Spread over a larger system, those costs weigh less on each watt. That is why a small system tends to show a higher price per watt than a large one from the same company.

An illustrative example, with made-up round numbers: if fixed costs were $6,000 and the rest of the job cost $2.00 per watt, a 4,000 W system would cost $14,000 ($3.50 per watt) and a 10,000 W system would cost $26,000 ($2.60 per watt). Real figures differ, but the pattern is why you should compare systems of similar size. Also ask how much of your yearly electricity use the system is designed to cover, since a bigger system is not automatically a better one for you.

Equipment

• Panels. Higher-efficiency panels usually cost more per watt but produce more from the same roof area, which helps when space is tight.
• Inverters. A single string inverter is the simplest and usually the cheapest. Microinverters or power optimizers cost more but handle shade and multiple roof faces better and allow panel-level monitoring.
• Mounting and wiring. Roof type, rail systems and conduit runs all add materials and labor.
• Batteries. A home battery can add a large amount to the quote. Always ask for the price with the battery and without it.

Your roof and your electrical panel

Roof material, pitch, number of faces, shading and age all change the work. Tile and very steep roofs take longer and carry more risk. A roof near the end of its life may need replacing before panels go on, because removing panels later costs money. An older main electrical panel may need an upgrade to carry the new system. Some installers list these as separate line items; others fold them into the price. Ask which it is, because it changes the per-watt figure you calculate.

Shade deserves a special mention. A tree or chimney that shades the roof for part of the day lowers production, and the fix (trimming, optimizers or a different layout) changes cost. Ask the installer how it measured shading, whether the design shows panel positions on a roof photo, and what annual production it expects. A cheaper design that loses a lot of output to shade can end up costing more per kilowatt-hour than a pricier one.

Roof work is another place to ask questions. If the installer will remove and reset panels later for a re-roof, find out what that costs. If a roofer is a separate company, ask who is responsible for leaks around the mounting points, and make sure the roofing warranty is not voided by the installation.

Labor, permits and local rules

Wages, permit fees, inspection rules and utility interconnection charges differ from city to city and state to state. Some local governments have streamlined solar permits, while others add steps and wait times. This is one reason the median price per watt differs between the states in this data set, and why a statewide figure is only a starting point for your own address.

The company's business model

Large national firms, regional contractors and small local crews have different overhead, marketing costs and buying power. A company that finds customers through door-to-door sales or paid online leads carries that cost somewhere. Some firms install with their own employees; others use subcontractors. None of these choices tells you anything about workmanship by itself, so use them as questions rather than conclusions: who will be on my roof, and who answers the phone after the install?

Sales structure is worth a direct question too. Ask whether the salesperson is paid on commission, whether the price in the quote is negotiable, and whether the same price would be offered through another channel. A quote that drops sharply when you say you are comparing is information about how the first number was set.

Financing and incentives

How you pay changes the total. A cash purchase has a single price. A loan may carry interest or a dealer fee that raises the contract price above the cash price. A lease or power purchase agreement has no purchase price at all, which is why this site leaves those systems out. Ask each installer for the cash price and for the full cost of any financing over its whole term.

Incentives also move the final cost, and the rules change. According to the IRS's residential clean energy credit page, that credit is not available for property placed in service after December 31, 2025. Other federal, state and utility programs, and the rules for net metering (how your utility credits power you send to the grid), vary and change. Check the current rules on official sites such as the Department of Energy's homeowner's guide, your state energy office and your utility, and ask a tax professional about your own situation.

Timing

Equipment prices, interest rates, tariffs and incentive programs shift over time. Historical prices, like those on this site, show where the market has been; they are not a forecast. The Tracking the Sun data we use ends with 2023 installs.

What to do with this

1. Ask each installer to itemize: panels, inverters, battery, mounting, roof and electrical work, permits, and financing charges.
2. Compute price per watt on the same scope and a similar size, using the method in how to compare solar quotes per watt.
3. Look up the installer's profile here to see how its past prices compared with the state's median, and ask about any large gap. A gap is a reason to ask a question, not a verdict.
4. Ask what is not included: a main panel upgrade, tree trimming, a re-roof, monitoring hardware, and the cost of removing and resetting panels later.
5. Before signing, work through how to check a solar installer.

Data documentation: LBNL Tracking the Sun. See also how to read the Tracking the Sun data.

Updated 2026-10-02.

General information only, current as of the date above. The information on Solar Price Atlas is not a recommendation or a guarantee of anyone's work. A license record shows registration status on the date shown, not workmanship, insurance coverage at the time of your job, or suitability for your project. Confirm license, insurance and permits directly before you hire. Rules and programs change; check the official sources linked in this guide.