Mokena, IL: the heat pump payback math

Here in Mokena, the honest answer is that a heat pump raises your annual running cost. $3,500 is what Mokena would pay extra to go electric rather than replace the furnace and AC with the same again, once the $2,000 federal credit is applied. Running costs here land $250 a year HIGHER than the furnace it replaces, so that premium is never recovered. That's Mokena's own climate and rates talking, not a hedge or a caveat.

Mokena's weather, in the numbers that matter

Mokena has a real but manageable winter — 4951 heating degree days a year against a 65°F base — and summers are hot enough that cooling matters as much as heating, at 1049 cooling degree days. Sizing runs off the design temperature, not the average day: -4°F here (record low -13°F), which works out to a seasonal COP of 2.6 for the cold-climate class of unit this climate calls for. Mokena needs the cold-climate class of unit: past a 25°F design temperature a standard heat pump falls back on resistance backup often enough to eat the savings. These numbers come from LEWIS UNIVERSITY AIRPORT, the closest NOAA station, 11.9 miles out.

The month-to-month numbers for Mokena

Electricity use for heating alone comes out to about 4,822 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $1,090 a year. That compares with roughly 52 Mcf a year of gas at Mokena's 11.25 per-Mcf rate — about $839 a year — against a local electricity rate of 19.06¢/kWh. Looked at as a full purchase rather than an incremental one, payback here is longer than the 15-year equipment life, leaving the 15-year total $7,254 behind.

Electric resistance heat in Mokena, compared

Not every home in Mokena has gas service. Compared with baseboard or electric-furnace resistance heat, the numbers shift in the heat pump’s favor. Switching saves about $1,559 a year here — a heat pump moving heat rather than generating it needs far less electricity than resistance coils — so the extra $8,000 spent up front comes back in about 5.1 years.

Mokena against the rest of the country

Mokena lands at position 814 out of 3206 cities on heating severity (coldest is 1), and 1932 out of 3206 by population size (biggest is 1). That's the coldest third of the dataset, where climate does most of the work behind this figure.

What to do with this number in Mokena

Mokena, Illinois is home to about 19,915 people, and the figures above are the same ones a local HVAC contractor uses to size and quote a system — this site doesn't guess where a real quote would land, it just tells you whether it's worth asking for one. In Mokena, nothing is lost by holding off until the current equipment genuinely fails.

Get quotes from local HVAC contractors before deciding.

Reading further on this page's numbers

Nothing above is a black box: the methodology guide shows the full arithmetic behind Mokena's 2.6 seasonal COP and payback figure. Mokena's -4°F design temperature is below the 25°F line, which is why a cold-climate unit is the right call here — see what that changes in the cold-climate unit guide.