Solar with a heat pump or electric heat in Illinois

It depends on the home and how cold it gets. Cold-climate heat pumps are rated to keep working efficiently in deep cold: NEEP's cold-climate specification requires a coefficient of performance above 1.75 at 5°F, meaning the heat pump still delivers well over a unit of heat for each unit of electricity. A Minnesota field study by the Center for Energy and Environment found space heating energy savings of 39% to 65% compared with the homes' previous heating.

Even so, a heat pump that replaces a gas furnace adds a lot of winter electricity, often several thousand kWh a year. As an example, 4,000 extra kWh a year takes about 3.3 kW of extra solar, or 9 panels, in the Chicago area. Use a full year of bills after the heat pump goes in, or your installer's load estimate, to size it.

Over a year, yes; in January, no. Short days and a low sun mean a December month produces roughly a third of a July month, and snow trims a little more. So the system makes its surplus in summer, when you may barely use the heat pump at all, and falls short in winter, when you use it most.

That makes the timing of your credits important. See solar in Illinois winters.

For systems on Illinois's older full net metering (connected before 2025), ComEd and Ameren track kWh credits over a 12-month annual period that ends after either the April or the October billing period, chosen by the customer, and unused credits expire at the end of it. For a heat pump home, an annual period ending in April lets summer surplus carry through the winter before the reset.

For systems connected since 2025, exports are credited at the supply rate, and the Illinois Solar Energy Association says those credits don't expire. Ask your installer and utility to confirm exactly how your credits roll over before you size the system. See Illinois net metering.

ComEd has separate delivery classes for homes with electric space heat, though the old discount has been gradually reduced. Ameren Illinois charges less for every kWh over 800 a month from October through May, on both supply and delivery: for October 2026–May 2027, supply is 10.4¢ for the first 800 kWh and 8.3¢ above.

For solar, that means each winter kWh your panels offset in an Ameren electric-heat home is worth a bit less than a summer kWh. It's one more reason to size on a full year of bills rather than a single month.

1. 1

   Start with 12 months of bills

   After the heat pump is installed if possible, or with your installer's estimate of its yearly use.

2. 2

   Pick the right annual period

   On older net metering, an April reset lets summer credits cover the winter.

3. 3

   Don't oversize for January

   Sizing to cover the coldest month leaves big summer surpluses earning only the supply-rate credit.

4. 4

   Consider a battery

   A battery stores daytime solar for evening use and qualifies for the utility storage rebate.

See adding solar for an EV or heat pump for more on sizing for new loads.