Your electric bill is full of terms and numbers that all add up to one thing. Electricity is expensive and is probably a major part of your monthly budget. Here are some tips and information that will help you understand how to be better stewards of the energy you use.

What is a Kilowatt-Hour (kWh)?

Easy, Right? Kilo is a prefix that means “thousand” so a Kilowatt is one-thousand watts.

But, here’s where it gets a bit more complicated. To completely unravel the meaning of a Kilowatt-hour, we have to look at three concepts – power, energy, and work. Although we tend to toss these terms around when talking about how much power we use and how to save it, it is important to understand that power and energy and work are not different terms for the same thing.

• Energy is the amount of work that can be done by a force — for our purposes, the force that we are considering is electric power. Energy is measured in units called “joules”. (Joules will never appear on your electric bill so don’t worry!)
• A joule is equal to the work required to continuously produce one watt of power for one second.
• Power is the rate that energy is used or generated. It is measured by dividing the amount of energy (measured in joules) by time. Power is expressed in watts

So, a watt is the rate that energy is used or generated and a kilowatt-hour (kWh). It is the base unit that electric companies use to measure the energy that your household or business uses. For every kilowatt-hour you see on your electric bill, you have moved the equivalent of 1000 watts through your electric meter for one hour (or 500 watts through your electric meter for two hours).

Since your electric bill reflects the amount of energy that you use over a period of time (most likely a month) reducing your total electric bill is a matter of reducing your consumption (consumption is a combination of how much and how fast you use energy).

This means that there are three ways that you you can conserve (use less) energy at home. You can:

• use less energy over the same amount of time (e.g. if you have a lightbulb that is on for one hour, reduce the amount of energy used by using a less powerful lightbulb)
• use the same amount of energy for less time (e.g. leave the lightbulb on for only half the time that it is usually on)
• combine these strategies and use less energy for a shorter period of time (e.g. use a less powerful lightbulb and leave it on for half the time you usually do).

Here are some practical examples to help you get a better grasp on the math used to calculate your monthly electric bill. For our calculations, we’ll assume that 1 kWh costs 11 cents. This is what the Department of Energy calculated the average cost of a kWh was in 2007. (If you look on your electric bill, you can determine the amount that you are paying for 1 kWh).

Let’s start with a 150 watt light bulb that you leave on for one hour

• Your total cost would be 150watts * 1 hour or 150 watt-hours.
• Converting this to kWh by dividing 150/1000 you get .15 kWh.
• Figuring out how much this lightbulb will cost you is done by:  .15kWh * .11 for each kWh = .0165 or about a penny and a half.

If you have ten 150 watt light bulbs to light your lobby, each of which are on for one hour, just multiply the result for one 150 watt bulb by 10. The result would be .165 or or 16 and one-half cents.

You might think that to reduce your expense you can reduce the amount of power you use which would allow you to leave your lights on longer. Here is why this doesn’t work:

Let’s say you switch to a 60-watt bulb but because it is getting darker sooner, you leave it on for 5 hours

• Your total costs would be 60watts * 5 hours or 300 watt-hours
• Convert this to kWh by dividing 300/1000 and you get .30 kWh
• Figure out how much this lightbulb costs is by multiplying .30 * .11 = .033 or a little more than three cents. This is twice the expense of our previous example.

On the surface, .01 or .03 doesn’t add up to much. But if you consider all the power consumed by your washer, dryer, stove and air conditioner as well as the power consumed by your lights, and combine them with how long they are used, you can see how fast your electric bill increases. You can also see that the only way to reduce your electric bill is to reduce the amount of power that each item uses as well as how long it is used.

Here’s another example:

Let’s say that you decide to air-condition a small office at your church using a window air conditioner. When you buy the air conditioner, look on the label (or you look at the air conditioner itself) and find that it uses 5.9 amps at 120 volts. With this information, you can calculate how much power (watts) it uses by multiplying 5.9 * 120 = 708 watts

If you run the air conditioner for 7 hours per day:

• Your total costs would be 708 watts * 7 hours or 4956 watt-hours per day
• Convert this to kWh by dividing 4956/1000 and you get 4.956 kWh per day
• Figure out how much the air conditioner will cost to run each day by multiplying 4.956 * .11 = .545 or about .55 cents per day.
• If you are planning to use the air conditioner 20 days per month, then your total cost per month would be .55 * 20 or $11.00

Note that your total cost may be less. That’s because the amount of power that the air conditioner draws (5.9 amps) is the maximum power it uses when it is actually cooling the air — not just running the fan to move air around.

Some Strategies for Reducing Your Electrical Costs

As we said before, there are only three ways that you can effectively reduce your energy costs — make them more efficient by reducing the amount of total energy that each of your appliances and lights uses, reducing the amount of time that the items are used or combining both these tactics.

Here is a quick checklist that you might consider when putting together a strategy for your church (or home) to be better stewards of the energy we have:

1. Many of today’s appliances draw power even when they are “off”. Look at all of these “phantom energy devices” and either unplug them when they are not in use or put them on power strips with strips. (Check your owner’s manual — especially for computers to see if the device can really be “turned off”).
2. As your light bulbs burn out (don’t trash perfectly good light bulbs), replace them with compact fluorescent (CF) bulbs. These CF bulbs provide the same amount of light using less power. If you are concerned with appearance and want to replace a group of bulbs all at once (say in a constantly lit lobby area) develop a program that removes the regular (incandescent) bulbs and uses them to replace bulbs as needed in areas where they are used for only short periods of time. Areas like closets, basements and storage rooms are good candidates for a “roll-over” program like this.
3. Start a program to replace standard light switches with light switches that sense if a room is occupied. These switches automatically turn off lights after a period of time if the room is not occupied and turn on the lights when someone walks into the room.
4. If you have refrigerators or freezers that are “underutilized”, consider combining their contents into a single place and turning off the unused refrigerators or freezers until they are needed (say right before the next potluck dinner).
5. A huge part of your energy bill is probably from heating and cooling. Work with your heating and cooling contractor to reduce that amount of energy you used to heat and cool the building. Raising the cooling temperature or reducing the heating temperature helps as does making sure that you heat and cool areas only when they are needed. Many areas of church buildings are only used for specific periods during the week. When they are not being used, automatically turning off or reducing heating or cooling can make a big difference in energy usage.
6. Check to see if your building is “leaking energy”. You can get a major energy audit of your building which will identify “energy-leaky” areas such as roofs and basements but you can also check your doors and windows to make sure that they close tightly, that the weather stripping is in good order and that the doors and windows themselves and are in good condition.
7. If you have different parts of your buildings that require different amounts of cooling and heating, make sure that these areas are closed off from one another. This makes your heating and cooling more efficient.
8. Heat water only when you need it. If you have restrooms that aren’t used during the week or kitchens that are not consistently used, consider putting a timer or a switch on your water-heater.
9. If you are doing any remodeling at all, add insulation and energy efficiency wherever and whenever you can. The cost of energy is only going to go up and whatever you do to reduce the amount of energy you use is going to free dollars to be used somewhere else in your church. Adding extra insulation, getting the most energy efficient appliances and devices you can purchase is always a good investment when it comes to saving energy.
10. If you have a large building with required “always-on” items such as safety lights and exit signs, consider replacing these with lower-energy equivalents. For example, exit signs that use incandescent bulbs use more electricity than new ones that use LEDs (light emitting diodes). With the formulas above, it is easy to calculate the pay back is for a replacement project such as this.

Much of the research and calculations for this article was done by Lea Chinn who is serving as a summer intern with Care of Creation. Lea is an Environmental Science major who is home for the summer.