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.
