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

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

5 tons central AC or heat pump, about 59,000 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 407 square feet in this climate. For a single room, size by the room: 29.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Palm Springs Asos (2.5 mi away). Jul is the hottest month, averaging a high of 108.6°F and a low of 79.4°F, with about 177 days a year at 90°F or more. That gives a design temperature of 117°F against 75°F inside.

What it costs to run

About 7,227 kWh a year at SEER2 14.3, or roughly $2,355 at California's average residential rate of 32.58¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in Cathedral City

Of the 59,000 BTU/hr, 30,240 comes through walls, roof and windows on a 117°F afternoon (51%), 13,000 is sun on the house (22%), 2,120 is four people and their appliances, and 13,600 is moisture the coil has to wring out of Cathedral City'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 45,360 BTU/hr before the moisture allowance.

Other house sizes in Cathedral City

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 10,300 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 17,700 BTU/hr.

Month by month in Cathedral City

Jul alone uses 20% of the year's cooling energy. The unit runs the equivalent of 1,753 hours a year at full output.

Cathedral City against nearby cities

Of 376 California cities here, Cathedral City has the 2nd highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Cathedral City's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Palm Springs Asos, 2.5 miles from the center of Cathedral City at 409 ft above sea level. That is close enough that the station's summers are Cathedral City's summers.

4 other cities use the same station and get the same climate inputs. The closest to Cathedral City: Palm Springs (5 mi away, 2.3 mi from the station), Rancho Mirage (5 mi away, 5.9 mi from the station), Palm Desert (9 mi away, 10 mi from the station), Desert Hot Springs (10 mi away, 9.6 mi from the station). Cathedral City is farther from the station than 1 of them.

The sun over Cathedral City in late July

At 33.84°N, the noon sun on 21 July stands 76.6° above the horizon over Cathedral City and the day runs 13 h 55 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.

52,517 people live in Cathedral City, the 171st largest of the 376 California cities sized on this site. Coordinates used: 33.8355, -116.4631.

Cathedral City AC sizing questions