What size AC for Chula Vista, CA? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 24,100 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 74% 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 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 996 square feet in this climate. For a single room, size by the room: 12.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at San Diego Brown Field (3.8 mi away). Aug is the hottest month, averaging a high of 80.6°F and a low of 63°F, with about 13 days a year at 90°F or more. That gives a design temperature of 85°F against 75°F inside.

What it costs to run

About 958 kWh a year at SEER2 14.3, or roughly $312 at California's average residential rate of 32.58¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Chula Vista

Of the 24,100 BTU/hr, 7,200 comes through walls, roof and windows on a 85°F afternoon (30%), 13,000 is sun on the house (54%), 2,120 is four people and their appliances, and 1,800 is moisture the coil has to wring out of Chula Vista's summer air (7%).

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 22,320 BTU/hr before the moisture allowance.

Other house sizes in Chula Vista

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,800 BTU/hr; a 350 sq ft living room needs about 4,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,300 BTU/hr.

Month by month in Chula Vista

Aug alone uses 29% of the year's cooling energy. The unit runs the equivalent of 568 hours a year at full output.

Chula Vista against nearby cities

Of 376 California cities here, Chula Vista has the 264th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Chula Vista's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is San Diego Brown Field, 3.8 miles from the center of Chula Vista at 521 ft above sea level. That is close enough that the station's summers are Chula Vista's summers.

No other city in this set uses San Diego Brown Field, so this sizing is Chula Vista's alone.

The sun over Chula Vista in late July

At 32.63°N, the noon sun on 21 July stands 77.8° above the horizon over Chula Vista 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.

278,546 people live in Chula Vista, the 15th largest of the 376 California cities sized on this site. Coordinates used: 32.6277, -117.0152.

Chula Vista AC sizing questions