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

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

2.5 tons central AC or heat pump, about 27,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 52% 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 866 square feet in this climate. For a single room, size by the room: 13.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Tehachapi 4 Se (3.2 mi away). Aug is the hottest month, averaging a high of 86.2°F and a low of 56.5°F, with about 28 days a year at 90°F or more. That gives a design temperature of 91°F against 75°F inside.

What it costs to run

About 792 kWh a year at SEER2 14.3, or roughly $258 at California's average residential rate of 32.58¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Tehachapi

Of the 27,700 BTU/hr, 11,520 comes through walls, roof and windows on a 91°F afternoon (42%), 13,000 is sun on the house (47%), 2,120 is four people and their appliances, and 1,100 is moisture the coil has to wring out of Tehachapi's summer air (4%).

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 26,640 BTU/hr before the moisture allowance.

Other house sizes in Tehachapi

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 8,300 BTU/hr.

Month by month in Tehachapi

Jul alone uses 35% of the year's cooling energy. The unit runs the equivalent of 409 hours a year at full output.

Tehachapi against nearby cities

Of 376 California cities here, Tehachapi has the 226th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Tehachapi's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Tehachapi 4 Se, 3.2 miles from the center of Tehachapi at 4,220 ft above sea level. That is close enough that the station's summers are Tehachapi's summers.

No other city in this set uses Tehachapi 4 Se, so this sizing is Tehachapi's alone.

The sun over Tehachapi in late July

At 35.14°N, the noon sun on 21 July stands 75.3° above the horizon over Tehachapi and the day runs 14 h 01 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.

11,114 people live in Tehachapi, the 364th largest of the 376 California cities sized on this site. Coordinates used: 35.1430, -118.4460.

Tehachapi AC sizing questions