What size AC for Rantoul, IL? 3 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Rantoul needs

3 tons central AC or heat pump, about 32,300 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 30% more than this climate needs. An oversized unit cools the air fast, shuts off before it pulls moisture out, and leaves the house cold and clammy.

If a contractor quotes you more than 3 tons for an average 2,000 sq ft house here, ask to see the Manual J load calculation behind it before you sign. That works out to one ton per 743 square feet in this climate. For a single room, size by the room: 16.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Rantoul (0.8 mi away). Jul is the hottest month, averaging a high of 87.5°F and a low of 64.1°F, with about 34 days a year at 90°F or more. That gives a design temperature of 93°F against 75°F inside.

What it costs to run

About 1,591 kWh a year at SEER2 14.3, or roughly $306 at Illinois's average residential rate of 19.23¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Rantoul

Of the 32,300 BTU/hr, 12,960 comes through walls, roof and windows on a 93°F afternoon (40%), 13,000 is sun on the house (40%), 2,120 is four people and their appliances, and 4,200 is moisture the coil has to wring out of Rantoul's summer air (13%).

Sun is the biggest share here, more than heat through the walls, so shading west windows and a light roof cut the size you need more than extra insulation would. Sensible heat totals 28,080 BTU/hr before the moisture allowance.

Other house sizes in Rantoul

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,400 BTU/hr; a 350 sq ft living room needs about 5,600 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,700 BTU/hr.

Month by month in Rantoul

Jul alone uses 29% of the year's cooling energy. The unit runs the equivalent of 704 hours a year at full output.

Rantoul against nearby cities

Of 225 Illinois cities here, Rantoul has the 24th highest cooling load. The range runs from Fox Lake at 24,900 BTU/hr to Granite City at 36,000.

Where Rantoul's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Rantoul, 0.8 miles from the center of Rantoul at 740 ft above sea level. That is close enough that the station's summers are Rantoul's summers.

No other city in this set uses Rantoul, so this sizing is Rantoul's alone.

The sun over Rantoul in late July

At 40.30°N, the noon sun on 21 July stands 70.1° above the horizon over Rantoul and the day runs 14 h 27 min from sunrise to sunset. A lower noon sun puts more of the day's heat on east and west walls than on the roof, which is why shading west glass pays off here. Shorter days give the house a longer night to shed the day's heat.

12,268 people live in Rantoul, the 195th largest of the 225 Illinois cities sized on this site. Coordinates used: 40.3026, -88.1549.

Rantoul AC sizing questions