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

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

2 tons central AC or heat pump, about 21,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 100% 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 1,143 square feet in this climate. For a single room, size by the room: 10.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Santa Monica Municipal Airport (17.9 mi away). Aug is the hottest month, averaging a high of 76.5°F and a low of 63.2°F, with about 5 days a year at 90°F or more. That gives a design temperature of 81°F against 75°F inside.

What it costs to run

About 800 kWh a year at SEER2 14.3, or roughly $261 at California's average residential rate of 32.58¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Malibu

Of the 21,000 BTU/hr, 4,320 comes through walls, roof and windows on a 81°F afternoon (21%), 13,000 is sun on the house (62%), 2,120 is four people and their appliances, and 1,600 is moisture the coil has to wring out of Malibu's summer air (8%).

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 19,440 BTU/hr before the moisture allowance.

Other house sizes in Malibu

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,600 BTU/hr; a 350 sq ft living room needs about 3,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 6,300 BTU/hr.

Month by month in Malibu

Aug alone uses 25% of the year's cooling energy. The unit runs the equivalent of 545 hours a year at full output.

Malibu against nearby cities

Of 376 California cities here, Malibu has the 321st highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Malibu's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Santa Monica Municipal Airport, 17.9 miles from the center of Malibu at 175 ft above sea level. That is close enough that the station's summers are Malibu's summers.

5 other cities use the same station and get the same climate inputs. The closest to Malibu: Santa Monica (15 mi away, 3 mi from the station), Los Angeles (20 mi away, 2.1 mi from the station), Beverly Hills (21 mi away, 4.8 mi from the station), Culver City (21 mi away, 3.1 mi from the station), West Hollywood (23 mi away, 6.3 mi from the station). Malibu is farther from the station than 5 of them.

The sun over Malibu in late July

At 34.03°N, the noon sun on 21 July stands 76.4° above the horizon over Malibu and the day runs 13 h 56 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.

10,298 people live in Malibu, the 372nd largest of the 376 California cities sized on this site. Coordinates used: 34.0259, -118.7596.

Malibu AC sizing questions