What size AC for Miami, FL? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 36,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 15% 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 3 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 657 square feet in this climate. For a single room, size by the room: 18.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Miami Beach (5.2 mi away). Aug is the hottest month, averaging a high of 88.1°F and a low of 78.1°F, with about 30 days a year at 90°F or more. That gives a design temperature of 93°F against 75°F inside.

What it costs to run

About 6,577 kWh a year at SEER2 14.3, or roughly $1,008 at Florida's average residential rate of 15.32¢ per kWh. Cooling runs 12 months of the year here.

What drives the load in Miami

Of the 36,500 BTU/hr, 12,960 comes through walls, roof and windows on a 93°F afternoon (36%), 13,000 is sun on the house (36%), 2,120 is four people and their appliances, and 8,400 is moisture the coil has to wring out of Miami's summer air (23%).

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 28,080 BTU/hr before the moisture allowance.

Other house sizes in Miami

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,700 BTU/hr; a 350 sq ft living room needs about 6,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,000 BTU/hr.

Month by month in Miami

Aug alone uses 13% of the year's cooling energy. The unit runs the equivalent of 2,576 hours a year at full output.

Miami against nearby cities

Of 173 Florida cities here, Miami has the 169th highest cooling load. The range runs from Miami Shores at 36,500 BTU/hr to Plant City at 44,900.

Where Miami's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Miami Beach, 5.2 miles from the center of Miami at 8 ft above sea level. That is close enough that the station's summers are Miami's summers.

3 other cities use the same station and get the same climate inputs. The closest to Miami: Miami Beach (4 mi away, 1 mi from the station), Miami Shores (7 mi away, 5 mi from the station), North Miami (9 mi away, 6.9 mi from the station). Miami is farther from the station than 2 of them.

The sun over Miami in late July

At 25.78°N, the noon sun on 21 July stands 84.6° above the horizon over Miami and the day runs 13 h 23 min from sunrise to sunset. With the sun that close to overhead, the roof takes most of the heat at midday and the west wall takes the rest after 3 pm. Shorter days give the house a longer night to shed the day's heat.

487,014 people live in Miami, the 2nd largest of the 173 Florida cities sized on this site. Coordinates used: 25.7752, -80.2086.

Miami AC sizing questions