Some use the terms *power* and *energy* interchangeably...

However, these terms represent very different, but related concepts.

*Power* is the **rate** at which energy is consumed, expressed in watts or kilowatts.

*Energy* is the **amount **of power consumed, expressed in watt-hours or kilowatt-hours (kWh).

To understand energy use, and consequently our utility bills, we must factor in the amount of *power* devices and appliances use and how long we use them.

Let’s look at the example of a typical light fixture outside your front door with a 60 watt light bulb. Sixty watts is the amount of *power* the lamp consumes, or the rate at which the lamp uses *energy*. If you run a 60 watt light bulb from dusk to dawn for 12 hours, you will consume 720 watt-hours of *energy* (or 0.72 kilowatt-hours).

In Southwest Florida we currently pay around 10 cents per kilowatt-hour, so that light bulb would cost 7.2 cents per night, or $26.28 annually.

If you look at your utility bill, you will see that you are charged for the number of kilowatt-hours (KWH) that you consume.

This is the amount of *energy* consumed between meter readings. To reduce the *energy* you use, you must either reduce the amount of *power* you use, or the amount of time you use that *power* (or both!)

**Energy = Power x Time**

Going back to our light bulb example, you could install a light bulb that uses less *power*, or you could reduce the number of hours it runs. Both courses of action would reduce the *energy* used and save you money. Here are three different ideas to save *energy* and money.

**1) Replace the bulb with a 13W compact fluorescent with equivalent light output (reduce power).**

Energy Saved: 0.56 kilowatt hours daily, or $20.58 saved annually

**2) Put the light on a timer and run for just 6 hours nightly (reduce time).**

Energy saved: 0.36 kilowatt hours daily, or $13.14 saved annuall

**3) Do both of the above (reduce power and time).**

Energy Saved: 0.64 kilowatt hours daily, or $23.43 saved annually

While *power* and *energy* are intimately connected, they are not the same.

Understanding the difference can help you save money!

In my next article, I will take this concept one step further and explain why you should think twice when trying to be “energy efficient.”