Answer
Energy Savings $=12936\frac{kW}{year}$
Cost Savings $=1358.28\frac{dollars}{year}$
Simple payback period $=0.25 years$
Work Step by Step
First we calculate the electric power reduction:
Electric power reduction $= (40W-34W)*700=4.2kW$
Taking in count the ballasts and the operating hoyrs the energy saving and the cost saving will be:
Energy Savings $=4.2kW*1.1*2800\frac{h}{year}=12936\frac{kW}{year}$
Cost Savings $=12936\frac{kW}{year}*0.105\frac{dollars}{kWh}=1358.28\frac{dollars}{year}$
The extra cost of buying high efficiency fluorescent lamps is:
Extra Cost $=700*(2.26dollars-1.77dollars)=343dollars$
Finally the simple payback period is:
Simple payback period $=\frac{343dollars}{1358.28\frac{dollars}{year}}=0.25 years$
