What size AC for Santa Paula, CA? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 23,300 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 80% 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 1,029 square feet in this climate. For a single room, size by the room: 11.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Camarillo Airport (10 mi away). Sep is the hottest month, averaging a high of 79.6°F and a low of 59.4°F, with about 9 days a year at 90°F or more. That gives a design temperature of 84°F against 75°F inside.

What it costs to run

About 839 kWh a year at SEER2 14.3, or roughly $273 at California's average residential rate of 32.58¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Santa Paula

Of the 23,300 BTU/hr, 6,480 comes through walls, roof and windows on a 84°F afternoon (28%), 13,000 is sun on the house (56%), 2,120 is four people and their appliances, and 1,700 is moisture the coil has to wring out of Santa Paula'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 21,600 BTU/hr before the moisture allowance.

Other house sizes in Santa Paula

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 4,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,000 BTU/hr.

Month by month in Santa Paula

Aug alone uses 25% of the year's cooling energy. The unit runs the equivalent of 514 hours a year at full output.

Santa Paula against nearby cities

Of 376 California cities here, Santa Paula has the 276th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Santa Paula's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Camarillo Airport, 10 miles from the center of Santa Paula at 71 ft above sea level. That is close enough that the station's summers are Santa Paula's summers.

4 other cities use the same station and get the same climate inputs. The closest to Santa Paula: Fillmore (9 mi away, 16.2 mi from the station), Camarillo (9 mi away, 3.2 mi from the station), Moorpark (12 mi away, 13.1 mi from the station), Thousand Oaks (16 mi away, 12.3 mi from the station). Santa Paula is farther from the station than 1 of them.

The sun over Santa Paula in late July

At 34.35°N, the noon sun on 21 July stands 76.0° above the horizon over Santa Paula 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.

31,786 people live in Santa Paula, the 235th largest of the 376 California cities sized on this site. Coordinates used: 34.3549, -119.0663.

Santa Paula AC sizing questions