What size AC for Cambridge, OH? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 28,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 50% 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 857 square feet in this climate. For a single room, size by the room: 14 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Cambridge (0.8 mi away). Jul is the hottest month, averaging a high of 85.1°F and a low of 62.7°F, with about 18 days a year at 90°F or more. That gives a design temperature of 90°F against 75°F inside.

What it costs to run

About 1,152 kWh a year at SEER2 14.3, or roughly $217 at Ohio's average residential rate of 18.81¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Cambridge

Of the 28,000 BTU/hr, 10,800 comes through walls, roof and windows on a 90°F afternoon (39%), 13,000 is sun on the house (46%), 2,120 is four people and their appliances, and 2,100 is moisture the coil has to wring out of Cambridge's summer air (8%).

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 25,920 BTU/hr before the moisture allowance.

Other house sizes in Cambridge

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 4,900 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,400 BTU/hr.

Month by month in Cambridge

Jul alone uses 31% of the year's cooling energy. The unit runs the equivalent of 589 hours a year at full output.

Cambridge against nearby cities

Of 176 Ohio cities here, Cambridge has the 104th highest cooling load. The range runs from Conneaut at 24,100 BTU/hr to Hamilton at 31,500.

Where Cambridge's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Cambridge, 0.8 miles from the center of Cambridge at 800 ft above sea level. That is close enough that the station's summers are Cambridge's summers.

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

The sun over Cambridge in late July

At 40.02°N, the noon sun on 21 July stands 70.4° above the horizon over Cambridge 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.

10,036 people live in Cambridge, the 176th largest of the 176 Ohio cities sized on this site. Coordinates used: 40.0209, -81.5855.

Cambridge AC sizing questions