Ask The Energy Expert
How Accurate Are Energy Calculators?
By Mary Jane Clark, Manager, Communications
Q. How accurate are home energy calculators?
A. Most of the energy calculators I've found base formulas on a set of assumptions. Mathematically, calculations may be correct. In practicality, many factors may be left out of these math equations that predict and calculate how you use energy in your home, in your life.
Calculating light bulb energy use is straightforward: watts x hours. However, if you have a high-efficiency heating and cooling system, you probably won't find a calculator that works for you. You won't find a Ground Source Heat Pump (GSHP, 20 SEER), or the latest EnergyStar Heat Pump (14.5 SEER or higher) in even the most sophisticated formulas, like the Home Energy Saver developed by the Lawrence Berkeley National Laboratory.
Many formulas let you choose from low to high efficiency, but if you find a calculator that does justice to a Dual Fuel Heat Pump or a GSHP, the most efficient system available according to "Mr. Electricity*," please let us know.
There are many web-based calculators available for lights and appliances as well as whole-house energy use. Formulas, as well as the energy-saving advice that may follow, vary widely. Here are some questions to consider when you use a web-based calculator: Does the formula take all of your appliances into account? Is your type of heating and cooling system listed as an option? Is the test home comparable in size and construction materials to your home? What climate zone or region is used?
Make sure you know what assumptions are behind the formula, if this is disclosed. Often, it is not.
Q. How can I determine how much an appliance uses?
A. There are several ways to get a realistic idea of how much energy an appliance may use. A few suggestions: (1) Refer to a guide based on average appliance use, such as the Home Energy Use Guide developed by Missouri's electric cooperatives, (2) Check the appliance Energy Guide label, or (3) Use a portable power monitor to test specific appliances.
Power monitors such as the "Kill-A- Watt" are becoming more widely available at hardware stores and online retailers. Prices start around $20. To get real readings, plug your appliance into the monitor, and plug the monitor into the wall for a period of time. If you measure the energy use for a full 24 hours, you should be able to determine how many kilowatt hours (kWhs) were used in a day, and multiply the kWhs by your average energy cost to get a realistic average daily energy cost.
We urge caution with power monitors that attach to your outdoor electric meter. With safety as our primary concern, we never recommend attaching equipment to our meter without our knowledge. It's also important for you to know that units recently demonstrated on TV news reports are not compatible with the Landis & Gyr electronic Focus meters we currently use. You will not get accurate information if the unit is not compatible.
When shopping for a new appliance, use the bright yellow Energy Guide label to compare and project operating costs of similar models. Be sure to check the energy rate, and use the calculation that best represents your costs — between 8¢ and 9¢, depending on how your home energy use fits into our Class A Residential Rate schedule.
Q. Does Cuivre River have tools that can help me analyze my energy costs?
A. We try to provide useful information on your electric bill (graphs, rates) and online through our electronic bill viewing option. If you call a billing or member services representative about your energy use, you can also obtain daily readings, appliance brochures, clip board audits and other information.
In addition, we invite you to visit the energy tips offered at www.cuivre.com, or visit www.TogetherWeSave.com for a home energy tour developed for cooperatives. Calculations here are based on your zip code and Cuivre River rates.
If you're calculating the payback for new high efficiency appliances and home heating and cooling systems, we encourage you to consider rebates and tax incentives that may be available to you. Paybacks through 2010 are better than ever for select appliances.
Energy use materials are available at any Cuivre River office. Here are some web sites that offer calculators. We're happy to review the assumptions with you if you have questions. Our goal is to help you find useful tools and resources you can use to make wise energy decisions.
Cooperative tools: www.TogetherWeSave.com
Energy Tips/Save Energy & Money: www.cuivre.com
U. S. Dept. of Energy: www.energysavers.gov
Energy conversions: www.tonto.eia.gov/kids/energy
Home Energy Savers: www.hes.lbl.gov
Mr. Electricity: www.michaelbluejay.com/electricity
Mary Jane Clark is Cuivre River's Manager of Communications and Current Times Editor. You can reach her at 800.392.3709, 636.528.8261, 636.695.4700 ext. 234, or contact an energy auditor at ext. 233, 272, 334, 4732, or 4733.