What size AC for Red Bluff, CA? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 42,200 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.5 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 568 square feet in this climate. For a single room, size by the room: 21.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Red Bluff Municipal Airport (1.6 mi away). Jul is the hottest month, averaging a high of 98°F and a low of 66°F, with about 104 days a year at 90°F or more. That gives a design temperature of 105°F against 75°F inside.

What it costs to run

About 2,676 kWh a year at SEER2 14.3, or roughly $872 at California's average residential rate of 32.58¢ per kWh. Cooling runs 6 months of the year here.

What drives the load in Red Bluff

Of the 42,200 BTU/hr, 21,600 comes through walls, roof and windows on a 105°F afternoon (51%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 5,500 is moisture the coil has to wring out of Red Bluff's summer air (13%).

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 36,720 BTU/hr before the moisture allowance.

Other house sizes in Red Bluff

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 7,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,700 BTU/hr.

Month by month in Red Bluff

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 906 hours a year at full output.

Red Bluff against nearby cities

Of 376 California cities here, Red Bluff has the 45th highest cooling load. The range runs from Corte Madera at 15,700 BTU/hr to Palm Desert at 59,000.

Where Red Bluff's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Red Bluff Municipal Airport, 1.6 miles from the center of Red Bluff at 354 ft above sea level. That is close enough that the station's summers are Red Bluff's summers.

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

The sun over Red Bluff in late July

At 40.17°N, the noon sun on 21 July stands 70.2° above the horizon over Red Bluff and the day runs 14 h 26 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.

14,286 people live in Red Bluff, the 330th largest of the 376 California cities sized on this site. Coordinates used: 40.1735, -122.2415.

Red Bluff AC sizing questions