What size AC for Clearlake, CA? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 32,900 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 27% 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 3 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 728 square feet in this climate. For a single room, size by the room: 16.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Clearlake 4 Se (4.3 mi away). Jul is the hottest month, averaging a high of 91.4°F and a low of 55.9°F, with about 66 days a year at 90°F or more. That gives a design temperature of 98°F against 75°F inside.

What it costs to run

About 991 kWh a year at SEER2 14.3, or roughly $323 at California's average residential rate of 32.58¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Clearlake

Of the 32,900 BTU/hr, 16,560 comes through walls, roof and windows on a 98°F afternoon (50%), 13,000 is sun on the house (40%), 2,120 is four people and their appliances, and 1,300 is moisture the coil has to wring out of Clearlake's summer air (4%).

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 31,680 BTU/hr before the moisture allowance.

Other house sizes in Clearlake

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,500 BTU/hr; a 350 sq ft living room needs about 5,800 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,900 BTU/hr.

Month by month in Clearlake

Jul alone uses 34% of the year's cooling energy. The unit runs the equivalent of 430 hours a year at full output.

Clearlake against nearby cities

Of 376 California cities here, Clearlake has the 150th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Clearlake's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Clearlake 4 Se, 4.3 miles from the center of Clearlake at 1,349 ft above sea level. That is close enough that the station's summers are Clearlake's summers.

No other city in this set uses Clearlake 4 Se, so this sizing is Clearlake's alone.

The sun over Clearlake in late July

At 38.96°N, the noon sun on 21 July stands 71.4° above the horizon over Clearlake and the day runs 14 h 20 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.

16,636 people live in Clearlake, the 320th largest of the 376 California cities sized on this site. Coordinates used: 38.9600, -122.6332.

Clearlake AC sizing questions