What size AC for Exeter, CA? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 41,400 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.5 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 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 580 square feet in this climate. For a single room, size by the room: 20.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Lindsay (8.1 mi away). Jul is the hottest month, averaging a high of 96.3°F and a low of 64.4°F, with about 116 days a year at 90°F or more. That gives a design temperature of 104°F against 75°F inside.

What it costs to run

About 2,361 kWh a year at SEER2 14.3, or roughly $769 at California's average residential rate of 32.58¢ per kWh. Cooling runs 6 months of the year here.

What drives the load in Exeter

Of the 41,400 BTU/hr, 20,880 comes through walls, roof and windows on a 104°F afternoon (50%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 5,400 is moisture the coil has to wring out of Exeter's summer air (13%).

Heat through the shell is the biggest share here, so insulation and air sealing cut the size you need more than shading would. Sensible heat totals 36,000 BTU/hr before the moisture allowance.

Other house sizes in Exeter

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,100 BTU/hr; a 350 sq ft living room needs about 7,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,400 BTU/hr.

Month by month in Exeter

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 815 hours a year at full output.

Exeter against nearby cities

Of 376 California cities here, Exeter has the 48th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Exeter's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Lindsay, 8.1 miles from the center of Exeter at 435 ft above sea level. That is close enough that the station's summers are Exeter's summers.

1 other city uses the same station and get the same climate inputs. The closest to Exeter: Lindsay (7 mi away, 2.2 mi from the station). Exeter is farther from the station than 1 of them.

The sun over Exeter in late July

At 36.29°N, the noon sun on 21 July stands 74.1° above the horizon over Exeter and the day runs 14 h 07 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.

10,186 people live in Exeter, the 375th largest of the 376 California cities sized on this site. Coordinates used: 36.2941, -119.1460.

Exeter AC sizing questions