How to Calculate Payback Period for Solar Panels & ROI

One of the strongest incentives to go solar is the prospect of saving money on your electricity bills and turning a profit over the life of your solar panels.

This article will outline a complete step-by-step overview of how to calculate your solar payback period and return on investment based on factors unique to your project, like local electricity costs and your personal energy usage habits.

What Is Solar Payback Period?

Your solar payback period is the time it takes to break even on your investment in solar.

When you go solar, you can reduce or completely eliminate your monthly electric bill. Those savings add up each month until they eventually pay back your investment in solar.

Your payback period is the amount of time for your energy savings to completely offset the costs of going solar. To figure this out, we want to account not only for up-front system costs but also for the cost of labor and any scheduled replacements of major components when their warranty is up.

How the Federal Solar Tax Credit Impacts Payback Period

The solar investment tax credit is a government program that offers a major financial incentive for going solar. Under the program, US residents who install solar can claim up to 30% of their total project costs as a credit toward their federal tax return.

That means that for every $10,000 you spend on solar, you’ll get a credit that erases $2,600 of your tax liability.

The solar tax credit is a major incentive that significantly speeds up your solar payback period. To be eligible to claim the credit, you must owe taxes on your return for the year that your system was installed. If your credit is larger than the amount of taxes you owe, the credit can be carried forward for up to 5 years.

When evaluating your investment in solar, be sure to factor the tax credit into your calculations if you are eligible.

Calculating the Payback Period for Solar Panels in a Grid-Tie System

Let’s walk through the payback period for solar panel calculations for a sample 7.2 kW grid-tie system built in Anaheim, CA (where GoGreenSolar is headquartered).

For the purpose of this example, let’s assume our system uses a SolarEdge HD-Wave inverter with a 12-year warranty. We’ll need to budget for one inverter replacement over the 25-year life of the panels.

Sample system specs: 7.2kW SolarEdge + PV Optimizer system

• System type: grid-tie
• System lifespan: 25 years
• Energy usage: 900 kWh / month
• Cost of electricity (in Anaheim, CA): 15.18 cents per kWh
• Cost of solar kit: $11,640
• Cost of wires & small parts (not included in kit; sourced from local hardware store): ~$500
• Cost of installation: $7,200 (or $0 for self-installed systems)
• Up-front system costs: $19,340
• 30% federal tax credit savings: $5,028.40
• Up-front costs after tax credit: $14,311.60
• Scheduled inverter replacement: ~$2,000
• Total lifetime costs: $16,311.60 (or $10,983.60 for self-installed systems)

Once we have added up our lifetime system costs, we can figure out how much money we expect to save on electric bills each month by multiplying monthly energy usage by the local cost of electricity:

900 kWh / month * 0.1518 = $136.62 monthly electric bill erased

Then, take the total lifetime cost of solar and divide it by your monthly savings to figure out when you will break even on your investment:

For DIY systems:

$10,983.60 / $136.62 = 80.4 months, or about 6.7 years

For professionally installed systems:

$16,311.60 / $136.62 = 119.4 months, or about 9.9 years

In this example, a DIY system would break even in about 6.7 years, leaving you with 18+ years of free power from solar. Hiring an installer would extend the payback period to 9.9 years, giving you 15+ years to reap the profits of free solar power.

Factors That Influence the Payback Period for Solar Panels

Here are some factors to take into consideration when calculating the payback period for solar panels:

Local Cost of Electricity

The cost of electricity varies by location, as each utility sets their own pricing and usage terms. The average cost of electricity can range anywhere from 9-32 cents per kWh (kilowatt-hour) depending on what state you live in.

If you live in an area with higher electricity costs, you’ll enjoy a faster payback period because you’re knocking out a larger electric bill each month.

States with low electricity costs can still see a positive return from going solar, but the payback period will be extended because the utility bill you’re offsetting isn’t as steep.

Sun Hours

Not all build sites are created equal; some get more sunlight than others. To use an extreme example, a solar system in the Arizona desert will be exposed to twice as much sunlight, and produce twice as much usable power, as one installed in the frigid reaches of Minnesota.

While grid-tie solar provides a positive return on investment no matter where you are in the US, the payback period will be extended in areas with low solar exposure. To see how many sun hours you get in your location, check NREL’s solar resource maps.

Product Warranties

When calculating payback period and ROI, be sure to account for any scheduled replacements over the life of the system. Specifically, batteries and certain inverters will need to be replaced at least once over the 25-year life of your panels.

In our example, we highlighted a SolarEdge HD-Wave system, which comes with a 12-year warranty. In comparison to microinverters like the Enphase IQ7+, a SolarEdge system will cost slightly less upfront.

However, the IQ7+ features a 25-year warranty, so it won’t need to be replaced. That makes microinverters more cost-effective over the life of the system.

DIY vs. Professional Installation

If you hire a professional to install your solar power system, you’ll likely be quoted a rate between $1 to $1.25 per watt for the job. For our sample 7.2 kW (7,200-watt) system, an installer would likely charge us $7,000-$9,000 for their labor.

That’s about one-third of the total project costs, and it extends the payback period for our system by more than three years!

If you feel inclined, you can skip out on those installation costs by purchasing a home solar kit and installing your own system. If you feel comfortable wiring an electrical outlet and climbing on your roof, installing solar should be well within your capabilities.

DIY installations typically require 2+ people and take 1-3 weekends to complete. It’s a great approach if you want to save money on your project and accelerate the amount of time it takes to break even on your investment in solar.

What Is Solar Panel ROI

Your solar ROI (Return on Investment) is your total savings on electricity costs once you’ve passed your payback date. Let's look at how to calculate solar panel ROI.

Calculating Solar ROI

Take your payback timeline and subtract it from 25 years, the expected lifespan of your system based on the standard length of solar panel warranties. Then, multiply by the amount of electric bills you knocked out by going solar.

Solar Panel ROI For DIY system

25 years - 6.7 years = 18.3 years

18.3 years * ($136.62/mo. * 12 mos.) = $30,001.75

In this example, if we opt for a DIY installation, we can expect our solar panels to save us $30k in electric bills over the life of the system.

Divide the net profit by the total cost of going solar to figure out your ROI:

$30,001.75 / $10,983.60 = 273.15% ROI

Solar Panel ROI for Professionally Installed System

25 years - 9.9 years = 15.1 years

15.1 years * ($136.62/mo. * 12 mos.) = $24,755.54

If we hire a professional installer, we can expect our solar panels to save us nearly $25k in electric bills over the life of the system.

Divide the net profit by the total cost of going solar to figure out your ROI:

$24,755.54 / $16,311.60 = 151.76% ROI

Solar Payback Period & ROI for Battery-Based Systems

The above examples highlight typical ROI calculations for a grid-tie solar system ‒- one that connects and stores power in the public utility grid. A grid-tie system is the most cost-effective option for homeowners looking to eliminate their electric bill.

Adding batteries to your system gives you a local energy storage option, giving you more independence and control over the power you generate. In grid-tie systems, a local battery bank provides backup power to keep appliances running during an outage. In off-grid systems, your battery bank is what allows you to deliver power to a remote location that can’t be reached by utility power.

Batteries are the most costly part of any solar system, which is why grid-tie homeowners often opt to skip them if their primary goal is to save on their monthly electric bills. If you choose to add batteries, know that it will extend your solar payback period, and you likely won’t turn a monetary profit from your solar panels.

However, the value of batteries shouldn’t be compared to the cost of grid power, but to the alternative of going without them. In grid-tie backup systems, batteries can be invaluable if you suffer frequent outages due to fierce storms or an unreliable power grid. In off-grid systems, solar + batteries is often cheaper than the cost of bringing a power line to your property or powering your home entirely off a gas generator.