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

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

2.5 tons central AC or heat pump, about 29,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 44% 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 822 square feet in this climate. For a single room, size by the room: 14.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Livermore Municipal Airport (11.8 mi away). Jul is the hottest month, averaging a high of 87.7°F and a low of 56.6°F, with about 52 days a year at 90°F or more. That gives a design temperature of 93°F against 75°F inside.

What it costs to run

About 1,065 kWh a year at SEER2 14.3, or roughly $347 at California's average residential rate of 32.58¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Danville

Of the 29,200 BTU/hr, 12,960 comes through walls, roof and windows on a 93°F afternoon (44%), 13,000 is sun on the house (45%), 2,120 is four people and their appliances, and 1,100 is moisture the coil has to wring out of Danville'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 28,080 BTU/hr before the moisture allowance.

Other house sizes in Danville

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,200 BTU/hr; a 350 sq ft living room needs about 5,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,800 BTU/hr.

Month by month in Danville

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 522 hours a year at full output.

Danville against nearby cities

Of 376 California cities here, Danville has the 195th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Danville's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Livermore Municipal Airport, 11.8 miles from the center of Danville at 393 ft above sea level. That is close enough that the station's summers are Danville's summers.

5 other cities use the same station and get the same climate inputs. The closest to Danville: San Ramon (4 mi away, 8.1 mi from the station), Dublin (8 mi away, 4.7 mi from the station), Pleasanton (11 mi away, 4 mi from the station), Livermore (14 mi away, 3 mi from the station), Brentwood (16 mi away, 17.6 mi from the station). Danville is farther from the station than 4 of them.

The sun over Danville in late July

At 37.81°N, the noon sun on 21 July stands 72.6° above the horizon over Danville and the day runs 14 h 14 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.

43,410 people live in Danville, the 200th largest of the 376 California cities sized on this site. Coordinates used: 37.8121, -121.9698.

Danville AC sizing questions