Actual cost for your facility will vary according to local energy and capital costs. While the simple payback for compact fluorescent bulbs is shorter, please note that the lifetime savings for L.E.D.'s is greater, making these the ideal retrofit. The most cost-effective lights to retrofit for energy efficiency are those that are used most frequently. After exit signs, the next place to look is the church office. Any incandescent bulbs used more than ten hours per week should be replaced with compact fluorescents.
Many common sizes are available in hardware stores and on the web.
Life Cycle Analysis Simple payback is not the entire story, however. Another method of looking at the cost of an energy efficiency upgrade is the lifetime savings. For example, the LED exit sign used in the example above will pay for itself in one year. But the fixture is guaranteed to last for ten years and laboratory tests show that it should last for at least 25 years. In addition, remember that the financial calculations made here are not complete.