What size AC for Carmel, IN? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 29,800 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 41% 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 805 square feet in this climate. For a single room, size by the room: 14.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Indianapolis Eagle Creek Airport (12.5 mi away). Jul is the hottest month, averaging a high of 85.2°F and a low of 66.7°F, with about 17 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 1,566 kWh a year at SEER2 14.3, or roughly $267 at Indiana's average residential rate of 17.04¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Carmel

Of the 29,800 BTU/hr, 10,800 comes through walls, roof and windows on a 90°F afternoon (36%), 13,000 is sun on the house (44%), 2,120 is four people and their appliances, and 3,900 is moisture the coil has to wring out of Carmel'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 25,920 BTU/hr before the moisture allowance.

Other house sizes in Carmel

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,200 BTU/hr; a 350 sq ft living room needs about 5,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,900 BTU/hr.

Month by month in Carmel

Jul alone uses 30% of the year's cooling energy. The unit runs the equivalent of 751 hours a year at full output.

Carmel against nearby cities

Of 88 Indiana cities here, Carmel has the 17th highest cooling load. The range runs from Auburn at 24,100 BTU/hr to Jasper at 36,400.

Where Carmel's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Indianapolis Eagle Creek Airport, 12.5 miles from the center of Carmel at 812 ft above sea level. That is close enough that the station's summers are Carmel's summers.

11 other cities use the same station and get the same climate inputs. The closest to Carmel: Westfield (5 mi away, 16.5 mi from the station), Zionsville (9 mi away, 11.6 mi from the station), Fishers (10 mi away, 19.8 mi from the station), Lawrence (11 mi away, 16.5 mi from the station), Whitestown (12 mi away, 10.9 mi from the station). Carmel is farther from the station than 6 of them.

The sun over Carmel in late July

At 39.97°N, the noon sun on 21 July stands 70.4° above the horizon over Carmel and the day runs 14 h 25 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.

103,606 people live in Carmel, the 6th largest of the 88 Indiana cities sized on this site. Coordinates used: 39.9655, -86.1484.

Carmel AC sizing questions