A solar system answers two separate financial questions: how much electricity it produces, which is mostly physics and geography, and what that electricity is worth, which is almost entirely a function of your utility's compensation policy. Conflating the two leads to overestimating what a system will actually save you.
Production first
The rooftop solar payback engine starts from your system's expected annual production, based on size, orientation, and local sun exposure, and compares the value of that production against the system's installed cost.
Export value is a policy decision, not a physics one
What happens to electricity you produce but do not use immediately depends entirely on your utility's rules. The solar export credit value engine lets you enter your actual export compensation rate directly, rather than assuming it matches your import rate.
Net metering versus buy-all, sell-all
Under net metering, exported electricity typically offsets future consumption at or near your retail rate. Under a buy-all, sell-all arrangement, you sell everything you produce at one rate and buy everything you use at another, usually higher, rate. The net metering versus buy-all, sell-all engine shows how differently the same system performs under each structure.
Degradation is real but modest
Panels lose a small percentage of output each year. The solar degradation impact engine applies that decline to your production estimate over a full ownership horizon, which matters more for a 25-year lifetime-savings projection than for a simple payback calculation focused on the first several years.
Finding the rate at which solar breaks even
Instead of assuming your current rate is the only relevant one, the solar breakeven electricity rate engine solves for the specific rate at which the system's cost is fully offset, letting you judge how much margin exists between that breakeven point and your actual rate.
Why two identical systems can have different economics
A system on a generous net-metering utility and an identical system on a buy-all, sell-all utility with a low export rate can have meaningfully different paybacks despite producing the exact same electricity. Confirm your specific utility's export policy before trusting a generic solar payback claim from a salesperson or a national average.
Frequently asked questions
If my system produces more than I use, do I get paid the same rate I pay for electricity?
Not necessarily. Net metering, where export credits equal your retail rate, is generous but not universal. Many utilities now pay a lower "avoided cost" rate for exported electricity, which is a meaningfully worse deal even for an identical system.
Does solar panel output degrade a lot over 25 years?
Most panels degrade gradually, commonly around 0.3-0.5% per year, so a system still produces the large majority of its original output after 25 years. It is a real effect worth modeling for a long-horizon payback, but it is not the dominant factor in most solar decisions.
What electricity rate should I use to check my solar breakeven?
Your actual current rate, and ideally a conservative view of how it might rise over your ownership horizon, since a higher future rate improves solar economics and a lower one worsens it. The breakeven engine solves for the specific rate at which the system clears.