What size AC for Havre de Grace, MD? 2.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Havre de Grace needs

2.5 tons central AC or heat pump, about 30,600 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 37% 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 783 square feet in this climate. For a single room, size by the room: 15.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Aberdeen Phillips Field (6 mi away). Jul is the hottest month, averaging a high of 86.4°F and a low of 67.7°F, with about 26 days a year at 90°F or more. That gives a design temperature of 91°F against 75°F inside.

What it costs to run

About 1,627 kWh a year at SEER2 14.3, or roughly $347 at Maryland's average residential rate of 21.31¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Havre de Grace

Of the 30,600 BTU/hr, 11,520 comes through walls, roof and windows on a 91°F afternoon (38%), 13,000 is sun on the house (42%), 2,120 is four people and their appliances, and 4,000 is moisture the coil has to wring out of Havre de Grace'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 26,640 BTU/hr before the moisture allowance.

Other house sizes in Havre de Grace

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,300 BTU/hr; a 350 sq ft living room needs about 5,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,200 BTU/hr.

Month by month in Havre de Grace

Jul alone uses 32% of the year's cooling energy. The unit runs the equivalent of 759 hours a year at full output.

Havre de Grace against nearby cities

Of 23 Maryland cities here, Havre de Grace has the 21st highest cooling load. The range runs from Westminster at 28,000 BTU/hr to Baltimore at 39,300.

Where Havre de Grace's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Aberdeen Phillips Field, 6 miles from the center of Havre de Grace at 57 ft above sea level. That is close enough that the station's summers are Havre de Grace's summers.

2 other cities use the same station and get the same climate inputs. The closest to Havre de Grace: Aberdeen (4 mi away, 3.1 mi from the station), Bel Air (12 mi away, 10.4 mi from the station). Havre de Grace is farther from the station than 1 of them.

The sun over Havre de Grace in late July

At 39.55°N, the noon sun on 21 July stands 70.9° above the horizon over Havre de Grace and the day runs 14 h 23 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.

15,222 people live in Havre de Grace, the 19th largest of the 23 Maryland cities sized on this site. Coordinates used: 39.5466, -76.1136.

Havre de Grace AC sizing questions