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

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

1.5 tons central AC or heat pump, about 18,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 125% 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 1,286 square feet in this climate. For a single room, size by the room: 9.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Oxnard Ventura County Airport (0.2 mi away). Aug is the hottest month, averaging a high of 73.5°F and a low of 60.6°F, with about 2 days a year at 90°F or more. That gives a design temperature of 78°F against 75°F inside.

What it costs to run

About 422 kWh a year at SEER2 14.3, or roughly $138 at California's average residential rate of 32.58¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Oxnard

Of the 18,700 BTU/hr, 2,160 comes through walls, roof and windows on a 78°F afternoon (12%), 13,000 is sun on the house (70%), 2,120 is four people and their appliances, and 1,400 is moisture the coil has to wring out of Oxnard'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 17,280 BTU/hr before the moisture allowance.

Other house sizes in Oxnard

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,400 BTU/hr; a 350 sq ft living room needs about 3,300 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 5,600 BTU/hr.

Month by month in Oxnard

Aug alone uses 23% of the year's cooling energy. The unit runs the equivalent of 324 hours a year at full output.

Oxnard against nearby cities

Of 376 California cities here, Oxnard has the 334th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Oxnard's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Oxnard Ventura County Airport, 0.2 miles from the center of Oxnard at 39 ft above sea level. That is close enough that the station's summers are Oxnard's summers.

2 other cities use the same station and get the same climate inputs. The closest to Oxnard: Port Hueneme (3 mi away, 2.6 mi from the station), San Buenaventura (Ventura) (5 mi away, 5.5 mi from the station). Oxnard sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Oxnard in late July

At 34.20°N, the noon sun on 21 July stands 76.2° above the horizon over Oxnard and the day runs 13 h 57 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.

200,616 people live in Oxnard, the 22nd largest of the 376 California cities sized on this site. Coordinates used: 34.1994, -119.2075.

Oxnard AC sizing questions