What size AC for Lancaster, PA? 2.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Lancaster 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 Lancaster Airport (5.4 mi away). Jul is the hottest month, averaging a high of 86.2°F and a low of 64.6°F, with about 18 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 1,368 kWh a year at SEER2 14.3, or roughly $289 at Pennsylvania's average residential rate of 21.13¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Lancaster

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 Lancaster'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 Lancaster

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 Lancaster

Jul alone uses 33% of the year's cooling energy. The unit runs the equivalent of 639 hours a year at full output.

Lancaster against nearby cities

Of 68 Pennsylvania cities here, Lancaster has the 13th highest cooling load. The range runs from St. Marys at 21,700 BTU/hr to Philadelphia at 34,300.

Where Lancaster's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Lancaster Airport, 5.4 miles from the center of Lancaster at 397 ft above sea level. That is close enough that the station's summers are Lancaster's summers.

3 other cities use the same station and get the same climate inputs. The closest to Lancaster: Columbia (10 mi away, 12.2 mi from the station), Ephrata (12 mi away, 7.3 mi from the station), Lebanon (22 mi away, 16.7 mi from the station). Lancaster sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Lancaster in late July

At 40.04°N, the noon sun on 21 July stands 70.4° above the horizon over Lancaster and the day runs 14 h 26 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.

58,441 people live in Lancaster, the 8th largest of the 68 Pennsylvania cities sized on this site. Coordinates used: 40.0421, -76.3010.

Lancaster AC sizing questions