What size AC for Menlo Park, CA? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 21,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 100% 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 1,145 square feet in this climate. For a single room, size by the room: 10.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Moffett Fed Airfield (7.5 mi away). Sep is the hottest month, averaging a high of 77.7°F and a low of 57.3°F, with about 9 days a year at 90°F or more. That gives a design temperature of 82°F against 75°F inside.

What it costs to run

About 537 kWh a year at SEER2 14.3, or roughly $175 at California's average residential rate of 32.58¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Menlo Park

Of the 21,000 BTU/hr, 5,040 comes through walls, roof and windows on a 82°F afternoon (24%), 13,000 is sun on the house (62%), 2,120 is four people and their appliances, and 800 is moisture the coil has to wring out of Menlo Park'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 20,160 BTU/hr before the moisture allowance.

Other house sizes in Menlo Park

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,600 BTU/hr; a 350 sq ft living room needs about 3,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 6,300 BTU/hr.

Month by month in Menlo Park

Aug alone uses 23% of the year's cooling energy. The unit runs the equivalent of 366 hours a year at full output.

Menlo Park against nearby cities

Of 376 California cities here, Menlo Park has the 317th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Menlo Park's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Moffett Fed Airfield, 7.5 miles from the center of Menlo Park at 39 ft above sea level. That is close enough that the station's summers are Menlo Park's summers.

8 other cities use the same station and get the same climate inputs. The closest to Menlo Park: East Palo Alto (1 mi away, 6.3 mi from the station), Palo Alto (6 mi away, 5.3 mi from the station), Newark (7 mi away, 6.9 mi from the station), Mountain View (7 mi away, 1.8 mi from the station), Los Altos (8 mi away, 3.7 mi from the station). Menlo Park is farther from the station than 7 of them.

The sun over Menlo Park in late July

At 37.48°N, the noon sun on 21 July stands 72.9° above the horizon over Menlo Park and the day runs 14 h 13 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.

33,040 people live in Menlo Park, the 227th largest of the 376 California cities sized on this site. Coordinates used: 37.4797, -122.1481.

Menlo Park AC sizing questions