11 May 2016

Air Conditioning Facts

Air-Conditioning Operating Costs

If you are interested in purchasing an air conditioner, chances are that comfort is the main reason. However, cost is also a major factor. You may want to calculate the annual cost of operating an air conditioner to determine whether it is worth the investment.

Factors affecting cost

Many factors affect the operating cost of an air conditioner:

• geographical location of the house
• variance of weather conditions from year to year
• efficiency rating of the air conditioner (SEER or EER)
• size of the air conditioner relative to house cooling load
• thermostat setting
• number of occupants in the house
• habits of people in the house – if windows are open or closed; if window shading is used; and frequency of appliance, cooking and lighting use
• local cost of electricity

Method of calculating annual energy cost

The output of an air conditioning unit is conventionally measured in tons. 1 ton = 12000 British Thermal units (BTU’s). So a 2 ton unit produces 24000 btus, a 2.5 ton unit produces 30000 btus, a 3 ton unit produces 36000 btus, etc.

The SEER rating is defined as the total cooling output of an air conditioning unit in British Thermal units divided by it’s total energy consumption in watt-hours

You can estimate the yearly cost to operate your central air conditioning system. In the Smiths Falls area the estimated cost of operation is calculated by:

(24 x DDc·18 / TOD – 18) x (CAP/ SEER) x (Cost/kW/1000)

Where,

DDc·18 = number of cooling degree-days (base 18°C) is 200

TOD = summer outdoor design temperature (°C) for location (SMITHS FALLS IS 30°C)

CAP = the capacity of the air conditioner (in Btu/h)

SEER = the rated seasonal energy efficiency ratio (Btu/h/W)

Cost per kWh = local electricity cost (in \$/kWh)

ESTIMATED COST PER YEAR FOR A 13 SEER 2 TON CENTRAL AIR:

(24 x 200/(30 – 18) x (24000/13) x (.18/1000) = \$132.92

ESTIMATED COST PER YEAR FOR A 14.5 SEER 2 TON CENTRAL AIR:

(24 x 200/(30 – 18) x (24000/14.5) x (.18/1000) = \$119.17

ESTIMATED COST PER YEAR FOR A 16 SEER 2 TON CENTRAL AIR:

(24 x 200/(30 – 18) x (24000/16) x (.18/1000) = \$108.00

The actual energy consumption can vary depending on several factors, including those listed in the previous section entitled “Factors affecting cost.” these are estimated yearly costs, based on .18 kWh. Your cost could be significantly higher if you choose to set your thermostat lower for example lower than 75°F (24°C).