What size AC for Draper, UT? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 38,100 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.2 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 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 630 square feet in this climate. For a single room, size by the room: 19 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Draper-Point Of Mountain (2 mi away). Jul is the hottest month, averaging a high of 93.5°F and a low of 65.5°F, with about 78 days a year at 90°F or more. That gives a design temperature of 100°F against 75°F inside.

What it costs to run

About 1,813 kWh a year at SEER2 14.3, or roughly $239 at Utah's average residential rate of 13.19¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Draper

Of the 38,100 BTU/hr, 18,000 comes through walls, roof and windows on a 100°F afternoon (47%), 13,000 is sun on the house (34%), 2,120 is four people and their appliances, and 5,000 is moisture the coil has to wring out of Draper's summer air (13%).

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 33,120 BTU/hr before the moisture allowance.

Other house sizes in Draper

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,900 BTU/hr; a 350 sq ft living room needs about 6,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,400 BTU/hr.

Month by month in Draper

Jul alone uses 35% of the year's cooling energy. The unit runs the equivalent of 681 hours a year at full output.

Draper against nearby cities

Of 67 Utah cities here, Draper has the 26th highest cooling load. The range runs from Heber at 30,700 BTU/hr to St. George at 49,200.

Where Draper's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Draper-Point Of Mountain, 2 miles from the center of Draper at 4,506 ft above sea level. That is close enough that the station's summers are Draper's summers.

1 other city uses the same station and get the same climate inputs. The closest to Draper: Bluffdale (4 mi away, 2.3 mi from the station). Draper sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Draper in late July

At 40.50°N, the noon sun on 21 July stands 69.9° above the horizon over Draper 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.

50,166 people live in Draper, the 19th largest of the 67 Utah cities sized on this site. Coordinates used: 40.4971, -111.8646.

Draper AC sizing questions