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

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

2 tons central AC or heat pump, about 25,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 64% 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 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 935 square feet in this climate. For a single room, size by the room: 12.8 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at London Fish Hatchery (3.8 mi away). Jul is the hottest month, averaging a high of 82.2°F and a low of 62.6°F, with about 13 days a year at 90°F or more. That gives a design temperature of 87°F against 75°F inside.

What it costs to run

About 968 kWh a year at SEER2 14.3, or roughly $182 at Ohio's average residential rate of 18.81¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in London

Of the 25,700 BTU/hr, 8,640 comes through walls, roof and windows on a 87°F afternoon (34%), 13,000 is sun on the house (51%), 2,120 is four people and their appliances, and 1,900 is moisture the coil has to wring out of London's summer air (7%).

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 23,760 BTU/hr before the moisture allowance.

Other house sizes in London

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,900 BTU/hr; a 350 sq ft living room needs about 4,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,700 BTU/hr.

Month by month in London

Jul alone uses 32% of the year's cooling energy. The unit runs the equivalent of 539 hours a year at full output.

London against nearby cities

Of 176 Ohio cities here, London has the 168th highest cooling load. The range runs from Conneaut at 24,100 BTU/hr to Hamilton at 31,500.

Where London's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is London Fish Hatchery, 3.8 miles from the center of London at 1,120 ft above sea level. That is close enough that the station's summers are London's summers.

No other city in this set uses London Fish Hatchery, so this sizing is London's alone.

The sun over London in late July

At 39.89°N, the noon sun on 21 July stands 70.5° above the horizon over London and the day runs 14 h 25 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.

10,743 people live in London, the 168th largest of the 176 Ohio cities sized on this site. Coordinates used: 39.8928, -83.4389.

London AC sizing questions