How Big of an Air Conditioner for a Mobile Home?

Window air-conditioner units are cheap to install but only effectively cool single rooms.

Determining the size of an HVAC (Heating-Ventilation-Air Conditioning) unit for a mobile home is a simple matter of measuring room size and calculating BTUs. The hardest part of selecting an AC unit is in choosing what type of unit to get: split-systems or central heat and air; window units; or mini-split ductless units. All are capable of cooling large areas if they are the proper size. Each has it's own list of benefits and downsides.

Square Footage

The first thing to do when considering an air conditioner is to measure the square footage of the house. Each room needs to be measured separately. Do not measure rooms that will not be cooled by the AC unit, such as closets. Including hallways, bathrooms, and laundry rooms, however, for whole-home cooling systems. Measure kitchens, dining rooms, and living rooms separately even if they are connected in an open-floor plan.

Converting Area to BTUs or Tonnage

Calculate the number of BTUs (British Thermal Units) needed for the square footage. AC units are ranked by BTUs or tonnage, depending on the type of system. Divide the total BTUs by 12,000 to determine the tonnage.

For 100 to 150 square feet, your AC unit should be rated at 5,000 BTUs. For 150 to 250 square feet, the unit should be rated at 6,000 BTUs. Rooms running 250 to 350 square feet need 7,000 BTU units. Add 4,000 BTUs for kitchens and 1,000 BTUs for bathrooms due to the additional heat generated in those rooms. Multiply rooms larger than 350 square feet by 25 to get the BTU requirements. Add each room's BTU needs together to determine the total BTUs for the house.

Window Units and Ductless Systems

Window units and mini-split, ductless systems are less expensive and easier to install than centralized systems. Most of these types are ranked by BTUs. Ductless systems involve putting wall units in the rooms that need to be cooled. The units connect through refrigerant pipes running through or along the walls to a condensor mounted outside the house. The unit is cheaper to install than typical central-air systems, as ducts do not need to be added to the house.

Window units are the least expensive and the easiest to install, but they only cool the rooms in which they are installed.

Both types of systems do not offer whole-house climate control and can only cool specific zones.

Split System

A split system is the typical AC unit. An external condensor mixes with internal elements and ducts to provide whole-house climate control. Installation of an external unit can be expensive, especially if ductwork needs to be installed. Most mobile homes come with duct work pre-installed, making the initial expense little more than the cost of the unit. Split systems are measured in tons. Be sure to get the right size for your home. Too small and the unit can burn up quickly. A unit that is too large will not remove humidity properly and will use more electricity than necessary.

References

• Consumer Energy Center: Window Air Conditioners
• Alpine Home Air: Selecting Air Conditioner Size