How much does it cost to run an air conditioner in Illinois?

Data checked October 2026

Short answer

A 3-ton central air conditioner in Illinois costs about $91.13 in July and $279 a year at 19.23¢/kWh; an 8,000 BTU window unit about $17.82 in July.

Illinois pays 19.23¢/kWh on average for Jan–Aug 2026 — 6% above the U.S. average of 18.19¢, the 16th most expensive of the 50 states and DC.
Illinois averages 875 cooling degree days a year against 1,216 nationally (NOAA), so we estimate 540 full-load cooling hours — 5.7 a day in July.
A new 3-ton split system sold for Illinois must reach at least SEER2 13.4 (DOE northern region); it draws about 2.69 kW on average and $0.52 an hour.
Moving up to the ENERGY STAR average of about SEER2 17 would cut the yearly bill to $220 — $59.04 a year less.
The average Illinois home used 722 kWh a month in 2025; this system adds 474 kWh in July.

Adjust it to your exact job

Your air conditioner

Type

Size

1 ton = 12,000 BTU/h. It's in the outdoor unit's model number: 24 = 2 ton, 36 = 3 ton, 48 = 4 ton.

Efficiency (SEER2)

Exact SEER2

New split systems sold for Illinois must be at least SEER2 13.4. SEER2 is on the EnergyGuide label or AHRI certificate.

How much it runs

Run time

540 full-load hours a year: DOE's 750-hour national basis × 875 cooling degree days in Illinois ÷ 1,216 U.S.

Electricity rate

Where you live

Price per kWh

EIA's state average: total residential revenue ÷ kWh sold, so delivery and fixed monthly charges are spread over every kWh.

3-ton central AC in July

$91.13a month

$279 a year (1,450 kWh) · $0.52 per hour running

At 19.23¢/kWh — Illinois average, Jan–Aug 2026 (EIA). That is 6% above the U.S. average of 18.19¢.

Per hour running: $0.522.69 kW average draw
Busiest month (Jul): 5.7 hfull-load hours a day
Per year: $279540 full-load hours
Capacity: 36,000BTU/hSEER2 13.4

Estimated monthly cost in Illinois

Same use, other efficiency

Yearly cost by efficiency rating
Efficiency	Per year	vs yours
SEER2 13.4 (min · North)	$279	—
SEER2 14.3 (min · South)	$261	−$17.55
SEER2 15.2 (ENERGY STAR)	$246	−$33.02
SEER2 17 (ES average)	$220	−$59.04

On a 95°F afternoon

SEER2 is a season average. At the hottest hours a typical 3-ton system (EER2 11.49) draws about 3.1 kW — $0.60 an hour.

How to cut it

Raise the thermostat a few degrees and run a ceiling fan instead — an ENERGY STAR fan uses about 35 W on high.
Change the filter and keep the outdoor coil clear of leaves and grass so the system moves heat as rated.
Close blinds on sun-facing windows in the afternoon, when cooling hours peak.

Energy budget

1,450 kWh 3-ton central AC — cooling season electricity540 full-load hours at 19.23¢/kWh$279

Estimated total$279

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Compare

Estimated monthly cooling cost in Illinois

Month	Full-load hours	3-ton central	8,000 BTU window
April	2	$0.96	$0.19
May	43	$22.31	$4.36
June	113	$58.31	$11.40
July	176	$91.13	$17.82
August	146	$75.52	$14.77
September	51	$26.13	$5.11
October	8	$4.14	$0.81

How this was worked out

DOE's room-AC test assumes 750 full-load hours a year for a typical U.S. home. We scale it by Illinois's population-weighted cooling degree days (875 ÷ 1,216) and spread it over the months the same way: 540 hours a year. Your thermostat setting and insulation move this a lot — switch the calculator to your own hours if you know them.

3 tons = 36,000 BTU/h ÷ SEER2 13.4 = 2,687 W. × 540 h = 1,450 kWh × 19.23¢ = $279.

The full method, material data and tips are on the main air conditioner cost calculator page.

More Illinois electricity costs

States with similar prices

Similar jobs

Other sizes people check

Sources

Data behind this answer

EIA Electric Power Monthly, Tables 5.6.A & 5.6.B — residential price by state (August 2026) — latest month and Jan–Aug 2026 year-to-date average for every state; preliminary, refreshed monthly · checked October 2026
ENERGY STAR certified room air conditioners (dataset) — average CEER by size for window units; 750 hours/yr label basis · checked October 2026
ENERGY STAR certified central AC & heat pumps (dataset) — 3-ton split average SEER2 17.06 / EER2 11.49 / HSPF2 8.44; 12k mini-split SEER2 22.81 · checked October 2026
10 CFR 430.32 — federal energy conservation standards (eCFR) — room AC CEER minimums from 2026-05-26; SEER2 regions; dehumidifier IEF; water heater UEF · checked October 2026
NOAA Climate Prediction Center — population-weighted state degree days — monthly normal heating and cooling degree days by state (base 65°F) · checked October 2026
EIA-861M sales and revenue by state — 2025 average household use and bill per state (U.S. 878 kWh, $151.88 a month) · checked October 2026
EIA Electric Power Monthly technical notes — average price = revenue ÷ sales, including fixed customer charges, fuel adjustments and surcharges · checked October 2026

Short answer

A 3-ton central air conditioner in Illinois costs about $91.13 in July and $279 a year at 19.23¢/kWh; an 8,000 BTU window unit about $17.82 in July.

Illinois pays 19.23¢/kWh on average for Jan–Aug 2026 — 6% above the U.S. average of 18.19¢, the 16th most expensive of the 50 states and DC.

Illinois averages 875 cooling degree days a year against 1,216 nationally (NOAA), so we estimate 540 full-load cooling hours — 5.7 a day in July.

A new 3-ton split system sold for Illinois must reach at least SEER2 13.4 (DOE northern region); it draws about 2.69 kW on average and $0.52 an hour.

Moving up to the ENERGY STAR average of about SEER2 17 would cut the yearly bill to $220 — $59.04 a year less.

The average Illinois home used 722 kWh a month in 2025; this system adds 474 kWh in July.

Adjust it to your exact job

Your air conditioner

Type

Size

1 ton = 12,000 BTU/h. It's in the outdoor unit's model number: 24 = 2 ton, 36 = 3 ton, 48 = 4 ton.

Efficiency (SEER2)

Exact SEER2

New split systems sold for Illinois must be at least SEER2 13.4. SEER2 is on the EnergyGuide label or AHRI certificate.

How much it runs

Run time

540 full-load hours a year: DOE's 750-hour national basis × 875 cooling degree days in Illinois ÷ 1,216 U.S.

Electricity rate

Where you live

Price per kWh

EIA's state average: total residential revenue ÷ kWh sold, so delivery and fixed monthly charges are spread over every kWh.

3-ton central AC in July

$91.13a month

$279 a year (1,450 kWh) · $0.52 per hour running

At 19.23¢/kWh — Illinois average, Jan–Aug 2026 (EIA). That is 6% above the U.S. average of 18.19¢.

Per hour running: $0.522.69 kW average draw
Busiest month (Jul): 5.7 hfull-load hours a day
Per year: $279540 full-load hours
Capacity: 36,000BTU/hSEER2 13.4

Estimated monthly cost in Illinois

Same use, other efficiency

Yearly cost by efficiency rating
Efficiency	Per year	vs yours
SEER2 13.4 (min · North)	$279	—
SEER2 14.3 (min · South)	$261	−$17.55
SEER2 15.2 (ENERGY STAR)	$246	−$33.02
SEER2 17 (ES average)	$220	−$59.04

On a 95°F afternoon

SEER2 is a season average. At the hottest hours a typical 3-ton system (EER2 11.49) draws about 3.1 kW — $0.60 an hour.

How to cut it

Raise the thermostat a few degrees and run a ceiling fan instead — an ENERGY STAR fan uses about 35 W on high.
Change the filter and keep the outdoor coil clear of leaves and grass so the system moves heat as rated.
Close blinds on sun-facing windows in the afternoon, when cooling hours peak.

Energy budget

1,450 kWh 3-ton central AC — cooling season electricity540 full-load hours at 19.23¢/kWh$279

Estimated total$279

Month

Full-load hours

3-ton central

8,000 BTU window

April

$0.96

$0.19

May

$22.31

$4.36

June

113

$58.31

$11.40

July

176

$91.13

$17.82

August

146

$75.52

$14.77

September

$26.13

$5.11

October

$4.14

$0.81

How this was worked out

3 tons = 36,000 BTU/h ÷ SEER2 13.4 = 2,687 W. × 540 h = 1,450 kWh × 19.23¢ = $279.

The full method, material data and tips are on the main air conditioner cost calculator page.