What size AC for South Lake Tahoe, CA? 2 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in South Lake Tahoe needs

2 tons central AC or heat pump, about 22,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 87% 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 1,068 square feet in this climate. For a single room, size by the room: 11.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at S Lake Tahoe Airport (2.2 mi away). Jul is the hottest month, averaging a high of 80.4°F and a low of 42.5°F, with about 1 day a year at 90°F or more. That gives a design temperature of 84°F against 75°F inside.

What it costs to run

About 37 kWh a year at SEER2 14.3, or roughly $12 at California's average residential rate of 32.58¢ per kWh. Cooling runs 0 months of the year here.

What drives the load in South Lake Tahoe

Of the 22,500 BTU/hr, 6,480 comes through walls, roof and windows on a 84°F afternoon (29%), 13,000 is sun on the house (58%), 2,120 is four people and their appliances, and 900 is moisture the coil has to wring out of South Lake Tahoe'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 21,600 BTU/hr before the moisture allowance.

Other house sizes in South Lake Tahoe

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,700 BTU/hr; a 350 sq ft living room needs about 3,900 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 6,700 BTU/hr.

Month by month in South Lake Tahoe

Jul alone uses 59% of the year's cooling energy. The unit runs the equivalent of 23 hours a year at full output.

South Lake Tahoe against nearby cities

Of 376 California cities here, South Lake Tahoe has the 286th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where South Lake Tahoe's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is S Lake Tahoe Airport, 2.2 miles from the center of South Lake Tahoe at 6,257 ft above sea level. That is close enough that the station's summers are South Lake Tahoe's summers.

No other city in this set uses S Lake Tahoe Airport, so this sizing is South Lake Tahoe's alone.

The sun over South Lake Tahoe in late July

At 38.93°N, the noon sun on 21 July stands 71.5° above the horizon over South Lake Tahoe 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.

21,225 people live in South Lake Tahoe, the 294th largest of the 376 California cities sized on this site. Coordinates used: 38.9282, -119.9810.

South Lake Tahoe AC sizing questions