What size AC for Spencer, IA? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 27,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 54% 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 882 square feet in this climate. For a single room, size by the room: 13.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Spencer Municipal Airport (3.2 mi away). Jul is the hottest month, averaging a high of 84.5°F and a low of 62.3°F, with about 19 days a year at 90°F or more. That gives a design temperature of 89°F against 75°F inside.

What it costs to run

About 1,010 kWh a year at SEER2 14.3, or roughly $147 at Iowa's average residential rate of 14.55¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Spencer

Of the 27,200 BTU/hr, 10,080 comes through walls, roof and windows on a 89°F afternoon (37%), 13,000 is sun on the house (48%), 2,120 is four people and their appliances, and 2,000 is moisture the coil has to wring out of Spencer'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 25,200 BTU/hr before the moisture allowance.

Other house sizes in Spencer

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,000 BTU/hr; a 350 sq ft living room needs about 4,800 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,200 BTU/hr.

Month by month in Spencer

Jul alone uses 35% of the year's cooling energy. The unit runs the equivalent of 530 hours a year at full output.

Spencer against nearby cities

Of 41 Iowa cities here, Spencer has the 25th highest cooling load. The range runs from Dubuque at 24,900 BTU/hr to Council Bluffs at 34,300.

Where Spencer's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Spencer Municipal Airport, 3.2 miles from the center of Spencer at 1,337 ft above sea level. That is close enough that the station's summers are Spencer's summers.

No other city in this set uses Spencer Municipal Airport, so this sizing is Spencer's alone.

The sun over Spencer in late July

At 43.15°N, the noon sun on 21 July stands 67.3° above the horizon over Spencer and the day runs 14 h 43 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. Long days mean the house keeps gaining heat into the evening, well after the outdoor peak.

11,418 people live in Spencer, the 37th largest of the 41 Iowa cities sized on this site. Coordinates used: 43.1470, -95.1527.

Spencer AC sizing questions