How to read the Tracking the Sun data

What this national laboratory data set contains, where it comes from, how we filtered it, and the limits to keep in mind when you read a profile.

Every number on this site comes from Tracking the Sun, a data set maintained by Lawrence Berkeley National Laboratory (LBNL), a U.S. Department of Energy national laboratory. It is one of the most complete public records of what grid-connected rooftop solar systems have cost in the United States. This guide explains what it is, how we used it, and what it cannot tell you. It is general information, not advice.

What the data set is

LBNL compiles records of individual solar installations from state agencies, utilities and incentive programs that report them. A record can include the install date, system size, total installed price, customer segment, ownership type, installer name, location, equipment and, where reported, battery details. We use the 2024 edition, which covers systems installed through 2023. The files are published openly, and LBNL documents the data on its Tracking the Sun page. We downloaded the public copy from the Department of Energy's Open Energy Data Initiative.

Because the records come from programs rather than from a census, coverage differs by state. Some states report almost every system; others report only systems in an incentive program; and some do not report prices or installer names at all. That is why this site covers only eight states.

Reporting also changes over time: a program may add or drop a reporting requirement, a state may stop collecting installer names, and the most recent year is often the least complete because applications are still being processed. For that reason we treat the latest year in each profile cautiously and show the latest install year so you can see how recent the data is.

What we kept

• Residential systems of 1 to 25 kW.
• Customer-owned systems, because for leases and power purchase agreements the reported "price" is not what a homeowner paid.
• Installs from 2019 to 2023, so older, much higher prices do not dominate.
• Eight states where the data names installers and reports prices: California, Arizona, New York, Massachusetts, Texas, Connecticut, New Mexico and Wisconsin.
• Installers with at least 15 such systems in a state, so a median means something.
• We excluded self-installed systems and dropped prices below $0.80 or above $12 per watt as likely errors.

How the price is defined

The price is the total installed price before incentives, divided by the DC size in watts. It is as reported to the program, so it may mean different things in different places: some programs record the contract price, others an estimate, and some may include items such as batteries or roof work in ways that are not always visible. We take the figure as reported.

Price per watt is also sensitive to size. Because fixed costs weigh more on small systems, an installer whose customers mostly have small systems will tend to show a higher median than one that installs large systems, even if both charge fairly. Each profile therefore shows the median system size so you can compare like with like.

Reading a profile: a worked example

The numbers below are illustrative, not from any real installer. Suppose a profile shows a median of $3.10 per watt, a middle range of $2.80 to $3.50, and a state median of $3.30. Reading it:

• Half of that installer's systems in the data were below $3.10 per watt and half above.
• The middle half of its systems fell between $2.80 and $3.50, so a quote at $3.40 would be within its usual spread.
• Its median is about 6% below the state median ($0.20 divided by $3.30). That is a description of the data, not a judgment: the installer might serve larger systems, simpler roofs or a different mix of equipment.

The range matters as much as the median. A wide range suggests very different jobs under one name, so a single number would mislead.

What the data cannot tell you

• Today's prices. The data stops at 2023 installs, and recent installs may be missing.
• Quality. Nothing in the data measures workmanship, customer service or reliability.
• Completeness. An installer's real volume may be larger than what the data shows, and some installers appear under several name variants that we merged only where the names were clearly the same.
• Scope. Systems with a battery, a roof replacement or a main panel upgrade can cost more per watt, and the data does not always say which ones had them.
• Contact details. There are no phone numbers or addresses. We place each installer under the town where it reported the most installs, which may not be where its office is.
• Licensing. Appearing in the data does not mean an installer is licensed. Check with your state.

Medians and ranges

The median is the middle value: half of the systems cost less per watt and half more. It is less sensitive to a few odd values than an average. We also show the 25th to 75th percentile range and compare the median with the state's median for the same group of systems, in percent. We do not call anyone expensive or cheap, because the data cannot say why a price differs.

Using it well

1. Treat the numbers as a reference range for your conversations with installers.
2. Do not treat a percentage gap from the state median as a ranking. Two installers can sit on either side of the median for good reasons.
3. Convert your own quote to price per watt using this method, with the same scope.
4. If a quote sits well outside the range, ask what explains it.
5. Read what affects the price of home solar for common reasons, and how to check a solar installer before you sign.

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.