Geothermal heat pumps and solar in Illinois

It trades heat with the ground, which stays at a steady temperature year-round, through a loop of buried pipe. The Department of Energy says geothermal systems reach efficiencies of 300% to 600% on the coldest winter nights and can use about 25% to 50% less energy than air-source heat pumps.

• Horizontal loops run in trenches at least four feet deep. DOE calls them generally the most cost-effective for homes with enough land.
• Vertical loops go down in boreholes. They cost more but need far less land and disturb less of the yard.
• Pond loops can be the least expensive option if the property has a suitable pond or lake.

DOE says the indoor components last up to about 24 years and ground loops 50 years or more.

EnergySage puts typical installed costs at $15,000 to $40,000 or more. Vertical systems need wells about 100 to 400 feet deep, and Fixr puts those at $20,000 to $70,000. A horizontal loop needs room: one manufacturer's spec sheet calls for about 750 to 1,500 square feet of land per ton of capacity, which is why estate lots suit it best.

The 30% federal credit is gone. IRS instructions say residential clean energy credits can't be claimed for expenditures made after December 31, 2025, and the Congressional Research Service notes an expenditure counts when installation is completed, so a 2025 deposit on a system finished in 2026 doesn't qualify. See the federal solar tax credit in 2026.

• Ameren Illinois lists discounts for ENERGY STAR closed-loop ground-source heat pumps of roughly $1,350 to $6,000 depending on system size, plus $500 for a desuperheater that helps heat water, limited to two per residential account. The contractor must buy through a participating distributor.
• ComEd has offered geothermal rebates through its energy efficiency program that require pre-approval through a participating contractor. Confirm the current amount with ComEd before you sign.
• A new state program is coming. The 2026 energy law directs the Illinois Power Agency to design a Geothermal Homes and Businesses Incentive Program, paid through geothermal renewable energy credits, with up to $10 million a year. It's still being designed.

Geothermal replaces gas with electricity, so your electric bill goes up even as total energy use falls. An NREL model of Upper Midwest retrofits found electricity use rose by roughly 5,900 kWh a year on average, with wide variation by house. Solar can offset much of that. See how many solar panels you need.

ComEd also charges homes with electric space heat less for delivery. For 2026, the Citizens Utility Board reports a distribution charge of 3.165¢ per kWh for single-family homes with electric heat, against 6.228¢ without, though the monthly customer charge is higher ($18.18 vs. $15.26). See solar with a heat pump or electric heat.

One caution: a geothermal system doesn't run in a power outage without backup power. See what a home battery can run.

Yes, for vertical loops. Under the Illinois Water Well Construction Code, a permit to build a closed-loop well system must come from the Illinois Department of Public Health, an approved local health department or an approved local government before work starts. The state fee is $100 for the first 10 boreholes and $10 for each one after that, and the driller must hold a state registration as a closed-loop well contractor. Contractors who only dig open trenches for horizontal loops are exempt from that registration. Your town will also want building and mechanical permits.