What size AC for Calexico, CA? 5 tons for 2,000 sq ft

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

5 tons central AC or heat pump, about 58,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, which falls short here. On a design day the unit runs flat out and the house still drifts above 75°F by late afternoon.

If a contractor quotes you more than 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 414 square feet in this climate. For a single room, size by the room: 29 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Imperial County Airport (11.4 mi away). Jul is the hottest month, averaging a high of 107.8°F and a low of 78.4°F, with about 181 days a year at 90°F or more. That gives a design temperature of 116°F against 75°F inside.

What it costs to run

About 6,538 kWh a year at SEER2 14.3, or roughly $2,130 at California's average residential rate of 32.58¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in Calexico

Of the 58,000 BTU/hr, 29,520 comes through walls, roof and windows on a 116°F afternoon (51%), 13,000 is sun on the house (22%), 2,120 is four people and their appliances, and 13,400 is moisture the coil has to wring out of Calexico's summer air (23%).

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 44,640 BTU/hr before the moisture allowance.

Other house sizes in Calexico

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 4,400 BTU/hr; a 350 sq ft living room needs about 10,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 17,400 BTU/hr.

Month by month in Calexico

Aug alone uses 21% of the year's cooling energy. The unit runs the equivalent of 1,611 hours a year at full output.

Calexico against nearby cities

Of 376 California cities here, Calexico has the 8th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Calexico's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Imperial County Airport, 11.4 miles from the center of Calexico at -55 ft above sea level. That is close enough that the station's summers are Calexico's summers.

3 other cities use the same station and get the same climate inputs. The closest to Calexico: El Centro (8 mi away, 3.5 mi from the station), Imperial (12 mi away, 0.4 mi from the station), Brawley (20 mi away, 10.3 mi from the station). Calexico is farther from the station than 3 of them.

The sun over Calexico in late July

At 32.68°N, the noon sun on 21 July stands 77.7° above the horizon over Calexico and the day runs 13 h 50 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.

38,744 people live in Calexico, the 208th largest of the 376 California cities sized on this site. Coordinates used: 32.6849, -115.4947.

Calexico AC sizing questions