Is your home a fit for solar in Illinois?

Your home may be a fit for solar if you own it, your power comes from Ameren Illinois, and your roof is in good shape. Sun matters too. A roof that faces south with little shade makes the most power. If your roof will need to be replaced soon, think about that first.

You can check each of those on your own, before anyone comes to look at the house.

Do you need to own your home?

Yes. The system goes on your roof, so you need to own the home. GSM Solar works only with homeowners.

That is true on a PPA too. PPA stands for power purchase agreement. On a PPA, the panels are owned by the solar company, not the homeowner. You buy the power they make at a set price per kWh. But they sit on your roof, and they stay there for as long as the contract runs. That is a choice only the owner of the house can make. See PPA, lease or buy.

Before you sign, the seller has to explain the type of agreement and how long it lasts. The contract also has to say what happens to the PPA if you sell the home. If you think you might move, read that part closely. See selling a home with solar.

If you rent, the roof is your landlord's call. The Department of Energy points renters to community solar, one shared solar array that many people can sign up for.

Does your power have to come from Ameren Illinois?

For GSM Solar to help, yes. GSM Solar works with homes in the Ameren Illinois service territory, in the Metro East and southern Illinois. To check yours, look at the top of your power bill. The company named there is your utility.

If a city utility or an electric co-op sends your bill, GSM Solar can't help with solar right now. The rules on this site may not match yours either. Illinois Shines says co-ops and city utilities may limit net metering or credit power a different way. Your utility can tell you how it handles solar.

Net metering is a credit on your bill for the power your panels send to the grid. In Ameren Illinois territory, a system that starts net metering on or after January 1, 2025 gets credit for supply charges only. Supply is the charge for the power itself. Our guide to net metering in Ameren Illinois explains what that credit covers. With solar, you stay a utility customer, responsible for a utility bill. Our utility bill guide explains why.

Is your roof in good enough shape for panels?

The Department of Energy says some roofs may not suit solar because of their age or tree cover. It says to think about the age of your roof and how long until it needs replacing.

Panels sit on top of the roofing. To put a new roof on, the panels have to come off first and go back up after. So if your roof is close to needing work, it is worth sorting out before panels go on.

If you don't know how old your roof is, look for paperwork from the last roof job. A home inspection report from when you bought the house may say too. Leaks, soft spots and missing shingles are worth noting as well.

The sellers have rules on this too. Illinois Shines is a state program that provides an incentive for solar projects. See how Illinois Shines works. The Illinois Power Agency's consumer protection handbook sets the rules for the companies that sell those projects, called Approved Vendors. For any project on a roof, it says the company must make sure the roof is in good enough condition for a solar project.

So a careful company looks at your roof up close. If it says the roof needs work first, ask what it saw. Also ask what your contract says about taking the panels off if the roof needs work later.

Which way does your roof face, and is it shaded?

The Department of Energy says panels work best on south-facing roofs with a slope between 15 and 40 degrees. Slope is how steep the roof is. Other roofs may work too. An east or west roof can still take panels, but the same panels make less power there than they would facing south.

The size, shape and slope of your roof also matter. A roof broken up by vents, chimneys or dormers has less open space for panels than a plain one.

Shade matters too. The Department of Energy says heavy shade from nearby trees can make rooftop panels a poor choice. Trees grow, so a tree that shades one corner today can shade more of the roof later.

You can check shade yourself. Look at the roof in the morning, at midday and late in the afternoon. Note where shadows from trees or the house next door land.

The company has to do this work too. The same handbook says the company must design the system around the roof's direction and shade before the contract steps begin. The handbook's words for direction are azimuth and orientation. Azimuth is the compass direction your roof faces. So the company should have a design for your own roof before you sign the Disclosure Form or a contract. Ask to see it. See the Disclosure Form and your right to cancel.

How much power does a kW of panels make in southern Illinois?

Two units come up here. A kW is the size of a system: how much power the panels can make at one moment. A kWh is an amount of energy. Your power bill counts kWh.

The Department of Energy points homeowners to PVWatts, a tool built at one of its national labs. PVWatts estimates how much power a solar system makes at any address. You tell it where the home is, which way the panels face and how steep the roof is. It gives back the kWh the panels would make in a typical year.

We ran PVWatts for one kW of panels on a south-facing roof. In Edwardsville it models about 1,395 kWh a year. In Marion it models about 1,407 kWh a year. A bigger system makes about that much for each kW it has. Tap either number for the exact inputs.

The answer grows with the size of the system, so more kW makes more kWh. Panels make less in winter, when days are short, and more in summer.

A model is not a measurement. It can't see the tree in your yard or the vent pipe on your roof. East or west roofs and shade make less than a south roof in full sun. The Department of Energy says these tools are a place to start, and to get a custom estimate for your own system, from a solar installer.

Every number on this site is listed with its source on our data page.

What can you check yourself before anyone comes out?

You can answer most of this from home in an afternoon:

• Your name is on the deed, so you own the home.
• The name at the top of your power bill is Ameren Illinois.
• You know about how old the roof is, or where the paperwork from the last roof job is.
• You know which side of the roof faces south, and whether that side is open.
• You know where shade from trees and nearby buildings falls during the day.
• You have thought about whether you might sell the home while a contract runs.

None of that replaces a company's own look at your roof. It does tell you what to ask about, and it helps you spot a quote that skipped a step. Who GSM Solar is, and what it does and doesn't do, is on our about page.

Quick answers

Do I need to own my home to get solar?

Yes. The system goes on your roof, so you need to own the home. If you rent, the Department of Energy points to community solar instead.

Does my power have to come from Ameren Illinois?

For GSM Solar to help, yes. Co-ops and city utilities may limit net metering or credit power a different way. If one of them sends your bill, ask it how it handles solar.

Does my roof have to face south?

No. South-facing roofs make the most power, but other roofs may work too. East and west roofs make less.

Should I think about my roof first?

Yes. Think about how old it is and how long until it needs replacing. The panels have to come off before a new roof goes on.

Does shade matter?

Yes. Heavy shade from nearby trees can make rooftop panels a poor choice. Look at where shadows fall in the morning, at midday and late in the day.

Is a PVWatts number what my system will make?

No. It is a model, not a measurement. Ask for a custom estimate for your own roof before you sign anything.