Thermostat settings by state

Thermostat settings in Illinois

By Ismail Farooq · Updated 2026-10-30

How most homes heat: Natural gas furnaces in most homes; boilers and radiators in older Chicago buildings.

Illinois winters are cold and windy, and summers hot and humid. Gas furnaces are the norm, so deep overnight setbacks are fine and save money. Many Chicago-area homes are older and have two-wire heating thermostats or boilers with radiators, so check for a C wire first.

Chicago two-flats and older houses often have a boiler for heat and a separate AC system, which means two thermostats or an Rh/Rc setup. Southern Illinois is zone 4A, warmer and more humid, where heat pumps work well.

Climate zones in Illinois

Zones follow county lines on the 2021 IECC map, and some counties changed zone between code editions. DOE’s Building America climate zone map lists every county.

Starting settings

• Everyday setpoints: about 68 °F in winter and 78 °F in summer while you’re home, set back while you sleep or are out (DOE’s guidance).
• Gas, oil or propane furnace or boiler: setbacks of 7 to 10 °F are fine; use the thermostat’s early-start feature so the house is warm on time.
• Heat pump: keep winter setbacks small (2 to 4 °F) so a cold morning doesn’t bring on aux heat.
• Humid summers: use fan Auto, not On, and turn on the thermostat’s dehumidify or overcool setting if the house feels damp. Keep indoor humidity under about 60%.
• Cold, damp winters: if you have a humidifier, let the thermostat lower its target as it gets colder outside so windows don’t drip.

Heat pump lockouts for Illinois

If you have a heat pump, these are starting points for the outdoor temperatures that control backup heat. Your installer’s balance point is better if you have it.

Rebates

Many utilities give rebates or bill credits for smart thermostats, sometimes in return for joining a peak-day program. Programs change often, so check your electric and gas utility’s website, or search by ZIP code in the ENERGY STAR rebate finder.