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Green Energy Solutions AC and Savings

Upgrading the efficiency of your residential air conditioner can save you money and reduce your carbon footprint. Assume that your old existing 3-ton air conditioner has an energy efficiency ratio (EER) of 8. Recall that EER is defined as the ratio of heat energy extracted (in Btu/hr) to the mechanical energy input (in watts). Assume that you operate the unit 3,500 hours per year and that the electricity cost is $0.14/kWh. There are 1,000 watts in a kilo watt (kW) and there are 12,000 Btu in a ton of refrigeration. Therefore, the current operating cost is:

kWh = 3,500 hours * 3 tons * 12,000 Btu/ton * (1/8 Btu/hr/watt) * (1/1,000)
kWh = 15,750 kWh
$ = 15,750 kWh * $0.14/kWh 
$  = $2,205

The operating cost of a new air conditioner with an EER of 14 would be:

kWh = 3,500 hours * 3 tons * 12,000 Btu/ton * (1/14 Btu/hr/watt) * (1/1,000)
kWh = 9,000 kWh
$ = 9,000 kWh * $0.14/kWh
$ = $1,260

This results in a first year savings of $945 and, combined with a tax credit along with future savings, could pay for installation of a new unit. Let’s look at another example using the above run hours and efficiency:

A #2 oil-fired electric generating station burning oil with a heating value of 19,600 Btu/#, a unit heat rate of 11,000 Btu/kWh and a carbon emission of 3.20 #CO2/# fuel, your existing (old air conditioner) carbon footprint could be calculated as follows:

#CO2 = 15,750 kWh * (1/19,600) * 11,000 * 3.2
#CO2  = 28,285 pounds of CO2 per year.

With the new air conditioner the carbon foot print would be:

#CO2 = 9,000 kWh * (1/19,600) * 11,000 * 3.2
#CO2 = 16,163 pounds of CO2 per year.

This results in a carbon footprint savings of 12,123 pounds of CO2 per year.

Save fuel, save money, and save the Earth.