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

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

3 tons central AC or heat pump, about 31,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 33% 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 763 square feet in this climate. For a single room, size by the room: 15.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Cumberland 2 (0.7 mi away). Jul is the hottest month, averaging a high of 87.1°F and a low of 64.4°F, with about 37 days a year at 90°F or more. That gives a design temperature of 92°F against 75°F inside.

What it costs to run

About 1,448 kWh a year at SEER2 14.3, or roughly $308 at Maryland's average residential rate of 21.31¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Cumberland

Of the 31,500 BTU/hr, 12,240 comes through walls, roof and windows on a 92°F afternoon (39%), 13,000 is sun on the house (41%), 2,120 is four people and their appliances, and 4,100 is moisture the coil has to wring out of Cumberland'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 27,360 BTU/hr before the moisture allowance.

Other house sizes in Cumberland

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,400 BTU/hr; a 350 sq ft living room needs about 5,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,400 BTU/hr.

Month by month in Cumberland

Jul alone uses 32% of the year's cooling energy. The unit runs the equivalent of 658 hours a year at full output.

Cumberland against nearby cities

Of 23 Maryland cities here, Cumberland has the 19th highest cooling load. The range runs from Westminster at 28,000 BTU/hr to Baltimore at 39,300.

Where Cumberland's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Cumberland 2, 0.7 miles from the center of Cumberland at 730 ft above sea level. That is close enough that the station's summers are Cumberland's summers.

No other city in this set uses Cumberland 2, so this sizing is Cumberland's alone.

The sun over Cumberland in late July

At 39.65°N, the noon sun on 21 July stands 70.7° above the horizon over Cumberland and the day runs 14 h 24 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.

18,643 people live in Cumberland, the 14th largest of the 23 Maryland cities sized on this site. Coordinates used: 39.6517, -78.7579.

Cumberland AC sizing questions