What size AC for Carpinteria, CA? 1.5 tons for 2,000 sq ft

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

1.5 tons central AC or heat pump, about 19,400 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 116% 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 1.5 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 1,235 square feet in this climate. For a single room, size by the room: 9.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Santa Barbara Municipal Airport (19.7 mi away). Aug is the hottest month, averaging a high of 74.5°F and a low of 58°F, with about 3 days a year at 90°F or more. That gives a design temperature of 79°F against 75°F inside.

What it costs to run

About 279 kWh a year at SEER2 14.3, or roughly $91 at California's average residential rate of 32.58¢ per kWh. Cooling runs 2 months of the year here.

What drives the load in Carpinteria

Of the 19,400 BTU/hr, 2,880 comes through walls, roof and windows on a 79°F afternoon (15%), 13,000 is sun on the house (67%), 2,120 is four people and their appliances, and 1,400 is moisture the coil has to wring out of Carpinteria'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 18,000 BTU/hr before the moisture allowance.

Other house sizes in Carpinteria

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,500 BTU/hr; a 350 sq ft living room needs about 3,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 5,800 BTU/hr.

Month by month in Carpinteria

Aug alone uses 29% of the year's cooling energy. The unit runs the equivalent of 205 hours a year at full output.

Carpinteria against nearby cities

Of 376 California cities here, Carpinteria has the 333rd highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Carpinteria's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Santa Barbara Municipal Airport, 19.7 miles from the center of Carpinteria at 8 ft above sea level. That is close enough that the station's summers are Carpinteria's summers.

2 other cities use the same station and get the same climate inputs. The closest to Carpinteria: Santa Barbara (12 mi away, 7.5 mi from the station), Goleta (21 mi away, 1.2 mi from the station). Carpinteria is farther from the station than 2 of them.

The sun over Carpinteria in late July

At 34.39°N, the noon sun on 21 July stands 76.0° above the horizon over Carpinteria and the day runs 13 h 58 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.

12,876 people live in Carpinteria, the 341st largest of the 376 California cities sized on this site. Coordinates used: 34.3852, -119.5008.

Carpinteria AC sizing questions