What size AC for Lehi, UT? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 34,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 23% 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 701 square feet in this climate. For a single room, size by the room: 17.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Utah Lake Lehi (4.2 mi away). Jul is the hottest month, averaging a high of 92.2°F and a low of 59°F, with about 50 days a year at 90°F or more. That gives a design temperature of 98°F against 75°F inside.

What it costs to run

About 1,028 kWh a year at SEER2 14.3, or roughly $136 at Utah's average residential rate of 13.19¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Lehi

Of the 34,200 BTU/hr, 16,560 comes through walls, roof and windows on a 98°F afternoon (48%), 13,000 is sun on the house (38%), 2,120 is four people and their appliances, and 2,500 is moisture the coil has to wring out of Lehi's summer air (7%).

Heat through the shell is the biggest share here, so insulation and air sealing cut the size you need more than shading would. Sensible heat totals 31,680 BTU/hr before the moisture allowance.

Other house sizes in Lehi

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,600 BTU/hr; a 350 sq ft living room needs about 6,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,300 BTU/hr.

Month by month in Lehi

Jul alone uses 42% of the year's cooling energy. The unit runs the equivalent of 430 hours a year at full output.

Lehi against nearby cities

Of 67 Utah cities here, Lehi has the 50th highest cooling load. The range runs from Heber at 30,700 BTU/hr to St. George at 49,200.

Where Lehi's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Utah Lake Lehi, 4.2 miles from the center of Lehi at 4,505 ft above sea level. That is close enough that the station's summers are Lehi's summers.

1 other city uses the same station and get the same climate inputs. The closest to Lehi: Saratoga Springs (6 mi away, 1.5 mi from the station). Lehi is farther from the station than 1 of them.

The sun over Lehi in late July

At 40.42°N, the noon sun on 21 July stands 70.0° above the horizon over Lehi and the day runs 14 h 28 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.

93,446 people live in Lehi, the 7th largest of the 67 Utah cities sized on this site. Coordinates used: 40.4171, -111.8711.

Lehi AC sizing questions