What size AC for La Plata, MD? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 34,300 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 23% 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 701 square feet in this climate. For a single room, size by the room: 17.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Quantico Mcas (18.3 mi away). Jul is the hottest month, averaging a high of 88°F and a low of 70.7°F, with about 30 days a year at 90°F or more. That gives a design temperature of 93°F against 75°F inside.

What it costs to run

About 2,229 kWh a year at SEER2 14.3, or roughly $475 at Maryland's average residential rate of 21.31¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in La Plata

Of the 34,300 BTU/hr, 12,960 comes through walls, roof and windows on a 93°F afternoon (38%), 13,000 is sun on the house (38%), 2,120 is four people and their appliances, and 6,200 is moisture the coil has to wring out of La Plata's summer air (18%).

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 28,080 BTU/hr before the moisture allowance.

Other house sizes in La Plata

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,600 BTU/hr; a 350 sq ft living room needs about 6,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,300 BTU/hr.

Month by month in La Plata

Jul alone uses 29% of the year's cooling energy. The unit runs the equivalent of 930 hours a year at full output.

La Plata against nearby cities

Of 23 Maryland cities here, La Plata has the 10th highest cooling load. The range runs from Westminster at 28,000 BTU/hr to Baltimore at 39,300.

Where La Plata's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Quantico Mcas, across the line in Virginia, 18.3 miles from the center of La Plata at 10 ft above sea level. That is close enough that the station's summers are La Plata's summers.

No other city in this set uses Quantico Mcas, so this sizing is La Plata's alone.

The sun over La Plata in late July

At 38.54°N, the noon sun on 21 July stands 71.9° above the horizon over La Plata and the day runs 14 h 18 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.

11,374 people live in La Plata, the 22nd largest of the 23 Maryland cities sized on this site. Coordinates used: 38.5435, -76.9698.

La Plata AC sizing questions