Plug-In Solar Calculator (US): Savings by State and Payback

This plug in solar calculator estimates what a plug-in kit could save in your home and how long it takes to pay for itself. Pick your state, enter your panel watts, how your panels are placed and the rate on your bill, and it returns yearly kWh, the share you use yourself, dollars saved per year and payback in years. It also shows your state’s legal cap and status.

Plug-in solar savings calculator

StatePanel power (W, DC)Add up the watts on the panel labels.How the panels are fixedAssumes the panels face south.ShadeWho is home in the day?Electricity price (cents per kWh)Kit price ($)Leave empty to skip payback.I rent my home

Your estimate per year

Panels produce: -
You use at home: -
Inverter limit: -
Payback: -

Email me this result

Data and assumptions

Sun: yearly output per kW of south-facing panels, PVGIS 5.3 (NSRDB), European Commission JRC, 14% system losses, read Nov 9, 2026.
Price: EIA Electric Power Monthly, Table 5.6.A, residential, August 2026 (a single summer month). Overwrite it with the rate on your bill.
Inverter limit: the cap in your state's law; where there is no law we use 1,200 W, the cap most state laws set. Panel power above 1.3 times the limit (1.6 times for upright panels, which rarely reach full power) is counted as lost.
Shade cuts output by 20% (partial) or 45% (heavy). Your share used at home is our assumption: 45%, 60% or 75% by daytime use. Power you do not use goes to the grid unpaid.
An estimate, not a quote. It cannot see your roofline, trees or appliances.

How It Works

The calculator does three things in order. It estimates how much your panels make, it works out how much of that your home uses, and it prices that energy at your rate.

Production comes from a solar yield dataset for a representative city in your state, adjusted for your panel direction, tilt and shade. Your rate starts as the average residential rate for your state and you can overwrite it with the number on your bill. The share you use yourself is our assumption, shown on screen and editable, because only you know what runs at midday.

Every dataset behind the result is named with the date we read it next to the result. If a number is an assumption of ours rather than a published figure, the calculator says so. We do not hide a default behind a total.

Your State’s Limit Matters

Your inverter’s AC output is what counts, not the label on the panels. States that have passed plug-in solar laws set a cap on that output, and the calculator clips your inverter to it.

Most cap it at 1,200 W. Utah’s HB 340 sets 1,200 W. Virginia sets 1,200 W per customer. Colorado is the exception at 1,920 W, with one system per home and one per outlet.

Some states add conditions that change what the calculator can tell you. Maine allows up to 1,200 W per home, but anything above 420 W needs a licensed electrician, a dedicated circuit and a notice to the utility. Vermont requires a smart meter. Virginia and Maryland require you to notify the utility before you install.

Start dates differ. Colorado’s took effect on August 12, 2026 and Virginia’s starts on January 1, 2027. We could not confirm Maine’s start date in the source, so check it before you buy.

States With No Law

If your state has not passed a plug-in solar law, the calculator shows No state law and still lets you run the numbers. There is no federal ban and no federal rule of its own. We did not find a state rule either way, so your utility’s interconnection process applies, and we could not check that utility by utility. Call yours before you plug in. Our state guides show what we found for each state, and Is plug-in solar legal in the US? has the full picture.

Why Export Usually Isn’t Paid

The calculator counts only the electricity you use yourself. That is deliberate. The new state laws mostly keep plug-in solar outside net metering, which is the system that pays for power sent back to the grid.

Utah’s law places plug-in kits outside net metering. Maine’s does too. Vermont goes further and says export is not paid. Connecticut requires a notice that export may be billed as consumption where there is no net metering meter.

So a watt your home does not use at that moment is worth little or nothing. That is why a kit tends to pay back faster in a home with steady daytime use, and why you should enter your real daytime consumption instead of a guess.

What the Calculator Can’t Know

It gives an estimate, not a quote. Here is what it cannot see:

Your shade. A tree, a wall or a neighbor’s roof can cut output a lot. You enter a level of shade; we cannot measure it.
Your daytime use. The self-use share is an assumption you can edit. A home with someone in all day uses more of its own power than an empty one.
Your actual rate. The default is a state average. Your bill may include tiers, time-of-use pricing or fixed charges that change the answer.
Your kit’s real output. Panels lose output in heat and over the years. Treat the result as a range.
Local rules. HOA, building and landlord rules are separate from state law.

If the calculator gives you an answer that looks too good, change the shade and self-use assumptions to something less friendly and see what is left. A kit that still pays back under cautious assumptions is a safer bet.

If You Rent

Rules and savings are different when you do not own the roof or the wall. A landlord can say no unless your state’s law says otherwise, and moving out takes the kit with you, which changes the payback sum. Tick “I rent” in the calculator and it will flag the points to check.

For the basics first, read what plug-in solar is and how it works in the US.

Sources

Each one opened and checked on November 9, 2026.

Questions people ask

Do plug-in solar panels actually save money?

Yes, when the power is used in your home. A plug-in kit offsets electricity you would otherwise buy while the sun shines. Export is usually not paid, so savings depend on how much of the output you use yourself, your state's rate and your sun and shade. Run your own numbers in the calculator above.

Is solar really cheaper than electricity?

Sometimes. A kit costs money up front, then produces power for free, so it can beat your utility rate over its life. Whether it does for you depends on the kit price, your rate per kWh, your sun and how much you use in daylight. The calculator shows payback in years.

How much will balcony solar cost?

Kit prices change quickly, so we do not print one here. Our comparison table shows prices read from each brand's own store with the date we read them. Enter the price you are quoted in the calculator and it will turn that into a payback figure for your state.