Shed Light on the Value of Solar with these Solar Calculators

Reader Contribution by Ryan Willemsen
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Solar calculators help you determine whether solar panels installed at your home or business will save money over electricity pulled from the grid. Calculators look at the cost of energy in your area, the type of panels you have or plan to install, weather patterns, and government incentives to determine energy cost savings.

You should use calculators as a convenient first look at the economics of going solar. However, a solar calculator is not a substitute for a consultation with a professional installer, but a compliment. A trusted installer will inform you about the advantages of different solar systems, issues with your property, and who will have the most up-to-date information about energy rates and incentives. A calculator will arm you with basic information going into this conversation, and also reveal questions you didn’t even realize you should ask.

Recommended Solar Calculators

Featured here are some of the most accurate and unbiased solar calculators on the web. Each entry provides the sponsor of the calculator, as well as a rundown of their features.  

Solar to the People

We discovered this straightforward solar calculator after reading LA Times coverage of Solar to the People’s study on California solar pricing. Of all the calculators listed here, we found  Solar to the People’s the easiest to use—definitely the best option if you’re just getting started. Simply enter an address and your utility cost, and Solar to the People generates a report of your expected solar savings for three different financing options: lease, loan, and purchase.

Despite the calculator’s simplicity, the financing options are a feature not found on the other calculators listed here. The amount of additional savings from an outright purchase versus a lease surprised us and probably isn’t something most consumers think about. It’s reassuring to see that you can save money on your energy bill even if you require a loan to purchase your solar system, but good to know you that if you can purchase the system outright, you will save considerably more money in the long-run.


The National Renewable Energy Laboratory (NREL) created perhaps the most industry-trusted solar calculator, PVWatts. To get started, PVWatts only asks for an address. From there PVWatts suggests weather data for your area (accepting the default is fine), and then prompts you for a substantial amount of information about your location and expected solar install, from the basic (your energy bill) to some more advanced questions (type of solar panels). Thankfully, PVWatts will generate an estimate even if you can’t answer all its questions. Hold onto the report it generates—you can fill in the blanks with your solar installer later.

In addition to total savings, PVWatts estimates the amount of energy your system will generate. The report also accounts for seasonal variation, which is significant even in temperate regions, given the shortened days. As an added convenience, all of this information is nicely formatted for print.

California Solar Initiative Incentive Calculators

The CSI-EPBB calculator is designed for two purposes: to estimate rebates offered for a given solar system by the California Solar Initiative (CSI) and to inform consumers about the differences in energy output and savings provided by different solar system types. While CSI-EPBB provides information not found on the aforementioned calculators, it is powered by PVWatts.

In brief, CSI-EPBB requests information similar to what you might enter into PVWatts, but also requests the type of photovoltaic (PV) system and electrical inverter (the device that converts solar-produced DC power to grid-friendly AC power), as this information affects the rebate offered by California.  

When you first jump into the solar market, you’ll probably be confused by some of the inputs CSI-EPBB requests (e.g. the type of PV module, or what a PV module even is). We’ve included it on our list because it can help you make and assess the information provided by solar installers.

Though in general it’s best to avoid inputting too much personal info into a solar calculator, CSI-EPBB is trustworthy, being sponsored by the California government, and uses your information to accurately assess energy output from your solar system, which in turn informs the financial incentive offered by the California Solar Initiative incentive program.

Most of the more technical information requested will be provided by your solar installer or in the documentation for your planned or existing solar system. This information includes info about the system itself—the types of panels used, the number of photovoltaic (PV) modules—as well as about the installation—Array tilt and azimuth (degrees of rotation from true north).

Once you’ve input information about your system and installation, CSI-EPBB returns a host of useful calculations about the energy your solar system will generate and the total state incentives. As with the information you input, some of these results are easy enough to understand—annual kWh produced by your system—while others—CEC-AC Rating, which warns if your system’s output exceeds the capacity of your inverter—may require some help deciphering, but are useful in planning your system and calculating expected savings. Most important to you will likely be the estimated total financial incentive you’ll receive for going solar. Just remember that this is an estimate—the California Incentive Program (and many similar programs) will ultimately look at your actual energy production.  

DSIRE (Database of State Incentives for Renewables & Efficiency)

DSIRE offers the most extensive information on US solar incentives and tax rebates, all without requesting any personal information or account creation. Note that DSIRE doesn’t host an actual solar calculator, but we included it here to help you understand the different state and regional incentives that should be included in any solar calculator you’re relying on for calculations. Because DSIRE is funded by the U.S. Department of Energy, it contains some of the most current information on solar policy and regulations.

Whereas PVWatts provide estimates of total savings, entering a zip code into DSIRE generates a comprehensive list of incentive programs for solar installation, as well as detailed entries about each program. DSIRE is most useful as a supplement to standard cost/savings calculators, as it will identify additional subsidies beyond the usual energy savings gained with solar. Listed programs include loans, financing, tax exemptions, rebates, as well as regulations that may encourage or impact your ability to install solar.

Choosing a Quality Solar Calculator

Free solar calculators can be found with a quick internet search, but not all calculators are created equal. Many are outdated, and as many more offer misleading information to steer consumers toward certain products.

This article recommended several trustworthy calculators. However, if you find a calculator you’d like to use that isn’t listed in this article—perhaps one specific to your region—think twice if it asks for contact information beyond an address and utilities cost. In rare cases, this is justified (as with California’s CSI calculator), but generally is a sign the calculator exists to fish for personal information.

Calculate with Confidence

While all calculators exist to help you determine whether solar panels are a good fit for your energy needs, you can find a range of calculators to address the concerns and questions you might have. Solar to the People provides a good first stop for assessing the financial benefit of going solar and is the best option for considering your financing options. A reliable calculator such as PVWatts will assess environmental factors such as sun exposure, installation type, and local energy costs to estimate expected savings from solar panel installation.  

Once you’ve decided to go solar, repositories such as DSIRE  can direct you to additional savings in the form of government incentives and rebates. Armed with more in-depth research about your energy needs and the range of available solar systems, a more sophisticated calculator hosted by a region or state, such as CSI-EPBB, can better educate you about the solar system that’s right for your property, as well as the range of regional financial incentives for which a system qualifies.

Just remember to use a trusted calculator, such as those featured here, as many web calculators are merely sales tools that generate biased estimates, or worse, exist solely to collect your personal info.  When in doubt, avoid it! If you have to enter anything more than an address and a power bill when running an estimate, it’s very possibly just a ploy to grab your personal information–an unfortunately common scam employed by online salespeople.

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