Calculating energy and carbon savings for lighting projects

Lighting projects tend to be lifetime driven. All compact florescent lamps (CFL) have a “mean time between failure” (MTBF) lifetime, which, on average, is about 5,000 hours. Light emitting diode (LED) lights also have a pre-calculated MTBP, although this number is significantly higher -- between 30,000 and 50,000 hours.

To determine the lifetime energy savings, we find the difference of wattage between the new light bulb and the one that it’s replacing and multiply that by the MTBF.

Example: If a 60 watt incandescent light bulb is replaced by a 15 watt CFL with a 5,000 hour MBTF, then the energy savings equals:

60 watts – 15 watts = 45 watts * 5,000 hours = 225,000 watt-hours = 225 kilowatt-hours

Customers pay for energy per kWh. In 2010, the nationwide average price for electricity was 11.53 ¢/kWh, meaning that the lighting improvements will save your organization nearly $26 per bulb. To more accurately predict savings, look at electricity prices in your state.

The amount of CO₂ used to generate a kWh of electricity is also location specific. However, for consistency sake, for its project calculations, NGE uses the national average of 1.31 lbs of CO₂/kWh. 

Example: 225 kWh * 1.31lbs of CO₂/kWh = 294.75 lbs of CO₂

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*Disclaimer: There are several different methods for calculating energy and carbon savings. The above described is the method most often used by New Generation Energy to determine figures for its project pages. Disagree with our calculation methods? Let us know in the comments below!