What size AC for Downey, CA? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 28,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 49% 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 853 square feet in this climate. For a single room, size by the room: 14.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Long Beach Daugherty Airport (8.8 mi away). Aug is the hottest month, averaging a high of 83.2°F and a low of 65.5°F, with about 23 days a year at 90°F or more. That gives a design temperature of 88°F against 75°F inside.

What it costs to run

About 1,620 kWh a year at SEER2 14.3, or roughly $528 at California's average residential rate of 32.58¢ per kWh. Cooling runs 6 months of the year here.

What drives the load in Downey

Of the 28,200 BTU/hr, 9,360 comes through walls, roof and windows on a 88°F afternoon (33%), 13,000 is sun on the house (46%), 2,120 is four people and their appliances, and 3,700 is moisture the coil has to wring out of Downey'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 24,480 BTU/hr before the moisture allowance.

Other house sizes in Downey

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,100 BTU/hr; a 350 sq ft living room needs about 4,900 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,500 BTU/hr.

Month by month in Downey

Aug alone uses 25% of the year's cooling energy. The unit runs the equivalent of 823 hours a year at full output.

Downey against nearby cities

Of 376 California cities here, Downey has the 217th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Downey's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Long Beach Daugherty Airport, 8.8 miles from the center of Downey at 34 ft above sea level. That is close enough that the station's summers are Downey's summers.

9 other cities use the same station and get the same climate inputs. The closest to Downey: Paramount (3 mi away, 6.1 mi from the station), Bellflower (3 mi away, 5.4 mi from the station), Artesia (6 mi away, 5.4 mi from the station), Lakewood (6 mi away, 2.8 mi from the station), Hawaiian Gardens (8 mi away, 4.4 mi from the station). Downey is farther from the station than 9 of them.

The sun over Downey in late July

At 33.94°N, the noon sun on 21 July stands 76.5° above the horizon over Downey and the day runs 13 h 56 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.

109,368 people live in Downey, the 62nd largest of the 376 California cities sized on this site. Coordinates used: 33.9382, -118.1309.

Downey AC sizing questions