What size AC for Tallahassee, FL? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 43,100 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.6 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 4 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 557 square feet in this climate. For a single room, size by the room: 21.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Tallahassee (6 mi away). Jul is the hottest month, averaging a high of 92.1°F and a low of 73°F, with about 103 days a year at 90°F or more. That gives a design temperature of 100°F against 75°F inside.

What it costs to run

About 4,333 kWh a year at SEER2 14.3, or roughly $664 at Florida's average residential rate of 15.32¢ per kWh. Cooling runs 8 months of the year here.

What drives the load in Tallahassee

Of the 43,100 BTU/hr, 18,000 comes through walls, roof and windows on a 100°F afternoon (42%), 13,000 is sun on the house (30%), 2,120 is four people and their appliances, and 9,900 is moisture the coil has to wring out of Tallahassee's summer air (23%).

Heat through the shell is the biggest share here, so insulation and air sealing cut the size you need more than shading would. Sensible heat totals 33,120 BTU/hr before the moisture allowance.

Other house sizes in Tallahassee

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,200 BTU/hr; a 350 sq ft living room needs about 7,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,900 BTU/hr.

Month by month in Tallahassee

Jul alone uses 20% of the year's cooling energy. The unit runs the equivalent of 1,439 hours a year at full output.

Tallahassee against nearby cities

Of 173 Florida cities here, Tallahassee has the 22nd highest cooling load. The range runs from Miami Shores at 36,500 BTU/hr to Plant City at 44,900.

Where Tallahassee's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Tallahassee, 6 miles from the center of Tallahassee at 177 ft above sea level. That is close enough that the station's summers are Tallahassee's summers.

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

The sun over Tallahassee in late July

At 30.45°N, the noon sun on 21 July stands 79.9° above the horizon over Tallahassee and the day runs 13 h 41 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.

205,089 people live in Tallahassee, the 9th largest of the 173 Florida cities sized on this site. Coordinates used: 30.4535, -84.2523.

Tallahassee AC sizing questions