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

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

2 tons central AC or heat pump, about 24,900 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 69% 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 965 square feet in this climate. For a single room, size by the room: 12.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at San Jose (9.1 mi away). Aug is the hottest month, averaging a high of 81.4°F and a low of 58.6°F, with about 16 days a year at 90°F or more. That gives a design temperature of 86°F against 75°F inside.

What it costs to run

About 814 kWh a year at SEER2 14.3, or roughly $265 at California's average residential rate of 32.58¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Los Gatos

Of the 24,900 BTU/hr, 7,920 comes through walls, roof and windows on a 86°F afternoon (32%), 13,000 is sun on the house (52%), 2,120 is four people and their appliances, and 1,800 is moisture the coil has to wring out of Los Gatos's summer air (7%).

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 23,040 BTU/hr before the moisture allowance.

Other house sizes in Los Gatos

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,900 BTU/hr; a 350 sq ft living room needs about 4,300 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,400 BTU/hr.

Month by month in Los Gatos

Aug alone uses 25% of the year's cooling energy. The unit runs the equivalent of 468 hours a year at full output.

Los Gatos against nearby cities

Of 376 California cities here, Los Gatos has the 262nd highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Los Gatos's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is San Jose, 9.1 miles from the center of Los Gatos at 49 ft above sea level. That is close enough that the station's summers are Los Gatos's summers.

5 other cities use the same station and get the same climate inputs. The closest to Los Gatos: Campbell (3 mi away, 5.7 mi from the station), Saratoga (5 mi away, 8.4 mi from the station), San Jose (9 mi away, 7.5 mi from the station), Santa Clara (9 mi away, 2.4 mi from the station), Milpitas (15 mi away, 5.4 mi from the station). Los Gatos is farther from the station than 5 of them.

The sun over Los Gatos in late July

At 37.23°N, the noon sun on 21 July stands 73.2° above the horizon over Los Gatos and the day runs 14 h 11 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.

32,952 people live in Los Gatos, the 228th largest of the 376 California cities sized on this site. Coordinates used: 37.2299, -121.9569.

Los Gatos AC sizing questions