What size AC for Lincoln, IL? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 28,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 50% 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 2.5 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 857 square feet in this climate. For a single room, size by the room: 14 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Lincoln (1.7 mi away). Jul is the hottest month, averaging a high of 85.5°F and a low of 63.8°F, with about 24 days a year at 90°F or more. That gives a design temperature of 90°F against 75°F inside.

What it costs to run

About 1,324 kWh a year at SEER2 14.3, or roughly $255 at Illinois's average residential rate of 19.23¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Lincoln

Of the 28,000 BTU/hr, 10,800 comes through walls, roof and windows on a 90°F afternoon (39%), 13,000 is sun on the house (46%), 2,120 is four people and their appliances, and 2,100 is moisture the coil has to wring out of Lincoln's summer air (8%).

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 25,920 BTU/hr before the moisture allowance.

Other house sizes in Lincoln

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,100 BTU/hr; a 350 sq ft living room needs about 4,900 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,400 BTU/hr.

Month by month in Lincoln

Jul alone uses 30% of the year's cooling energy. The unit runs the equivalent of 676 hours a year at full output.

Lincoln against nearby cities

Of 225 Illinois cities here, Lincoln has the 163rd highest cooling load. The range runs from Fox Lake at 24,900 BTU/hr to Granite City at 36,000.

Where Lincoln's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Lincoln, 1.7 miles from the center of Lincoln at 583 ft above sea level. That is close enough that the station's summers are Lincoln's summers.

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

The sun over Lincoln in late July

At 40.15°N, the noon sun on 21 July stands 70.2° above the horizon over Lincoln and the day runs 14 h 26 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.

13,047 people live in Lincoln, the 185th largest of the 225 Illinois cities sized on this site. Coordinates used: 40.1507, -89.3703.

Lincoln AC sizing questions