What size AC for Fort Walton Beach, FL? 3.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Fort Walton Beach needs

3.5 tons central AC or heat pump, about 40,200 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.4 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 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 596 square feet in this climate. For a single room, size by the room: 20.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Destin Fort Walton Beach Airport (9.4 mi away). Jul is the hottest month, averaging a high of 90.9°F and a low of 76.2°F, with about 50 days a year at 90°F or more. That gives a design temperature of 97°F against 75°F inside.

What it costs to run

About 4,612 kWh a year at SEER2 14.3, or roughly $707 at Florida's average residential rate of 15.32¢ per kWh. Cooling runs 8 months of the year here.

What drives the load in Fort Walton Beach

Of the 40,200 BTU/hr, 15,840 comes through walls, roof and windows on a 97°F afternoon (39%), 13,000 is sun on the house (32%), 2,120 is four people and their appliances, and 9,300 is moisture the coil has to wring out of Fort Walton Beach'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 30,960 BTU/hr before the moisture allowance.

Other house sizes in Fort Walton Beach

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,000 BTU/hr; a 350 sq ft living room needs about 7,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,100 BTU/hr.

Month by month in Fort Walton Beach

Jul alone uses 20% of the year's cooling energy. The unit runs the equivalent of 1,639 hours a year at full output.

Fort Walton Beach against nearby cities

Of 173 Florida cities here, Fort Walton Beach has the 115th highest cooling load. The range runs from Miami Shores at 36,500 BTU/hr to Plant City at 44,900.

Where Fort Walton Beach's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Destin Fort Walton Beach Airport, 9.4 miles from the center of Fort Walton Beach at 18 ft above sea level. That is close enough that the station's summers are Fort Walton Beach's summers.

2 other cities use the same station and get the same climate inputs. The closest to Fort Walton Beach: Destin (9 mi away, 0.8 mi from the station), Niceville (11 mi away, 9.4 mi from the station). Fort Walton Beach is farther from the station than 1 of them.

The sun over Fort Walton Beach in late July

At 30.42°N, the noon sun on 21 July stands 80.0° above the horizon over Fort Walton Beach 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.

21,188 people live in Fort Walton Beach, the 117th largest of the 173 Florida cities sized on this site. Coordinates used: 30.4249, -86.6218.

Fort Walton Beach AC sizing questions