Calculation Assumptions for CFLs Category Value Data Source Power ENERGY STAR Qualified Unit Initial Cost per Unit $ average of available products found in EPA research, 2008 Wattage watts calculated   watts calculated   watts calculated   watts calculated   watts calculated Bulb Life hours LBNL 2007   hours LBNL 2007   hours LBNL 2007   hours LBNL 2007 Lifetime For hour CFL years calculated For hour CFL years calculated For hour CFL years calculated For hour CFL years calculated   Conventional Unit Initial Cost per Unit $ average of available products found in EPA research, 2009 Wattage watts LBNL 2007   watts LBNL 2007   watts LBNL 2007   watts LBNL 2007   watts LBNL 2007 Bulb Life hours LBNL 2007   hours LBNL 2007 Lifetime For hour incandescent bulb years calculated For hour incandescent bulb years calculated   Maintenance Labor cost (per hour) $ EPA 2004 Installation labor hours hours Assumption   Usage Hours used per day hours/day LBNL 2007 Number of days per year days/year Assumption CFL annual bulb replacements hours bulbs/year Calculated hours bulbs/year Calculated hours bulbs/year Calculated hours bulbs/year Calculated Incandescent annual bulb replacements hours bulbs/year Calculated hours bulbs/year Calculated   Discount Rate Commercial and Residential Discount Rate (real) % A real discount rate of percent is assumed, which is roughly equivalent to the nominal discount rate of percent ( percent real discount rate + 3 percent inflation rate)   Energy Prices Commercial Electricity Price $ $/kWh Energy Information Administration, Annual Energy Outlook 2009 (Early Release) edition (converted from 2007 to 2008). Residential Electricity Price $ $/kWh APS   Carbon Dioxide Emissions Factors Electricity Carbon Emission Factors lbs CO2/kWh APS   CO2 Equivalents Annual CO2 sequestration per forested acre 9,700 lbs CO2/acre-yr EPA's Greenhouse Gas Equivalencies Calculator. Annual CO2 emissions for "average" passenger car 12,037 lbs CO2/acre-yr EPA's Greenhouse Gas Equivalencies Calculator.   Disclaimer The estimated savings from switching to CFLs is based on user inputs for bulb usage and an average cost of $ per kWh. Actual savings will vary depending on your actual usage and electricity rate plan.   Home | About APS | Residential Services | Business Services My Community | Supplier Diversity & Development Contact Us | Web Survey | Site Map