What size AC for Lemon Grove, CA? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 27,300 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 54% 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 2.5 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 878 square feet in this climate. For a single room, size by the room: 13.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at San Diego Montgomery Field (8.2 mi away). Aug is the hottest month, averaging a high of 82°F and a low of 65.3°F, with about 16 days a year at 90°F or more. That gives a design temperature of 87°F against 75°F inside.

What it costs to run

About 1,416 kWh a year at SEER2 14.3, or roughly $461 at California's average residential rate of 32.58¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Lemon Grove

Of the 27,300 BTU/hr, 8,640 comes through walls, roof and windows on a 87°F afternoon (32%), 13,000 is sun on the house (48%), 2,120 is four people and their appliances, and 3,600 is moisture the coil has to wring out of Lemon Grove's summer air (13%).

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 23,760 BTU/hr before the moisture allowance.

Other house sizes in Lemon Grove

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,100 BTU/hr; a 350 sq ft living room needs about 4,800 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,200 BTU/hr.

Month by month in Lemon Grove

Aug alone uses 26% of the year's cooling energy. The unit runs the equivalent of 741 hours a year at full output.

Lemon Grove against nearby cities

Of 376 California cities here, Lemon Grove has the 231st highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Lemon Grove's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is San Diego Montgomery Field, 8.2 miles from the center of Lemon Grove at 418 ft above sea level. That is close enough that the station's summers are Lemon Grove's summers.

3 other cities use the same station and get the same climate inputs. The closest to Lemon Grove: La Mesa (3 mi away, 7.4 mi from the station), El Cajon (6 mi away, 10.3 mi from the station), San Diego (8 mi away, 1.5 mi from the station). Lemon Grove is farther from the station than 2 of them.

The sun over Lemon Grove in late July

At 32.73°N, the noon sun on 21 July stands 77.7° above the horizon over Lemon Grove and the day runs 13 h 51 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.

27,867 people live in Lemon Grove, the 253rd largest of the 376 California cities sized on this site. Coordinates used: 32.7331, -117.0344.

Lemon Grove AC sizing questions