Answer: It´s called "payback" for people who want to make energy efficient upgrades. It´s a way of determining how a product´s higher checkout cost is offset by the energy dollars saved. For products that use energy, such as light bulbs or even a refrigerator, the higher cost at the store can prove to be lower over the time of usage. These items use electricity every day and electricity costs money.

Take the light bulb for example. Based on research, a 60-watt incandescent light bulb costs approximately $0.35 at a typical home center. An energy efficient 15-watt compact fluorescent bulb, which corresponds to the same light output as the 60-watt, costs approximately $12.99.

In addition to the price, another difference is the lifetime energy costs. Again, according to research, in one month, you will spend approximately $2.94 to light the 60-watt bulb (at $0.07 per kilowatt hour) and approximately $0.84 to light the 15-watt bulb (at $0.07 per kilowatt hour). The energy efficient option costs $2.10 less to operate in just one month. In six months, the energy efficient option has paid you back and makes up the initial price difference. This is calculated by dividing the extra cost at the store ($12.64) by the $2.10 monthly savings.

Compact fluorescent light bulbs use 70% less energy, last up to ten times longer and produce 75% less heat than incandescent light bulbs. This type of bulb comes in different sizes and shapes and is suitable for indoors and outdoors.

So, you have to evaluate what is better for your particular situation. People on a strict budget may choose to pay less upfront and more over time.