First, because you'll be looking at Energy Guide stickers on the new refrigerators, to determine which ones will be the cheapest to run, and you might as well have an idea of how they compare to the one you're using now.



Second, if you are expecting to replace your fridge primarily to save electricity, you may find that you don't need to. Although current refrigerators are far more energy efficient than those of a decade back, your fridge may prove to be efficient enough that there isn't a compelling motivation to upgrade. You might save more energy, for the same price, on adding insulation or a new window or two.

Third, you may find that your old fridge burns so much electricity, that a refrigerator tune-up will save you electricity even in the few short weeks before you buy the new refrigerator. Actions that can really help are: checking the door gaskets for leaks or cracks, checking the temperature (38-40F for refrigerator, 5F for freezer), making sure the compressor and coils are dust free; and ensuring good airflow around the unit. Even if you discover that your current fridge is an energy pig and you do a tune-up, you might discover that the tune-up on its own will mean big electricity savings.

Your old fridge could conceivably be costing you $25 to $125 a year more than it ought to, and your new fridge may prove to be less efficient than its Energy Guide label claims, depending on how you use it. But if you merely assume that a fridge consumes what its label claims, you'll be leaving a lot of savings on the table. Knowledge is key.

What if I told you that $20 could save you at least $35 a year, year after year? It turns out that there is an affordable tool that can do just what we need: measure the energy use of your refrigerator.

I purchased a Kill A Watt meter about five years back and have used it to measure the electricity consumption of many appliances in my house. I have also lent it to many others so they could uncover energy savings of their own. These meters and other power monitors like them are available for about $20 and they tell you how many kilowatt hours per day (kwh/day) an appliance like a refrigerator uses. A measurement takes about three days, because a refrigerator cycles on and off, and only a longer measurement levels the peaks and troughs of the fridge's electrical use. But once you have that measurement, you will know what your fridge uses and you can start choosing actions to save energy, or you will be able to make a more sound choice about replacing your existing fridge.

The Kill A Watt meter measures electricity use in several ways. The key readings for our purposes are time elapsed and kilowatt hours consumed. The Kill A Watt meter measures both of these values from the moment it is plugged in, so if you plug in the meter, then plug your refrigerator into that immediately, you'll start to see how much electricity your fridge is using once at least 24 hours have passed. Here's the process:

1. Pull your fridge out from the wall. Unplug it and plug an extension cord into the outlet instead.

2. Plug the Kill A Watt meter into the other end of the extension cord, and the refrigerator into that. Leave the meter where you can see it.

3. Push the refrigerator back. (You can just plug the Kill A Watt meter between the wall outlet and the refrigerator, if that enables you to see the unit while you're taking the measurement.)

4. Wait at least a full day to measure. Ideally you should wait 48 to 96 hours. If you keep pressing the red button on the meter you will see readings for, among others, the hours and minutes elapsed, and the kilowatt hours consumed. You can calculate kilowatt hours per day using this formula:

kwh/day = kwh / ((hours/24)+(minutes/1440))

So if the final reading is 2.37 kwh and the elapsed hours is 34h22m, the kwh/day would be 2.37 / ((34/24)+(22/1440)), or 1.655 kwh/day. Don't wait more than four days to do your final reading, because the time elapsed measurement wraps back to zero at 99h59m.

Most fridges are rated in terms of kwh consumed per year, so to compare your current fridge with what's available now, you can multiply the kwh/day result by 365. Our hypothetical fridge getting 1.655 kwh/day consumes 604 kwh/year. A 16 cubic foot Sun Frost fridge, in contrast - one of the most efficient refrigerators available - consumes only 254 kwh/year.

You can see how your old refrigerator compares to new models by searching the www.energystar.gov database, for models that share features of your fridge. Fridge efficiency standards have increased in recent years, and a refrigerator usually uses more energy as it ages, because of worn gaskets, dust buildup on compressor and coils, wear and tear on the motor, and sometimes loss of refrigerant. And ENERGY STAR rated refrigerators must be at least 20% better than the standard, so if you have an old fridge that was not ENERGY STAR rated when you bought it, you can see there is a big potential for savings, especially if you know your current consumption.

The efficiency standard for refrigerators varies based on type (top or bottom freezer, side-by-side, or no freezer), volume, defrost capabilities, and coolant type. And the formula is so complicated that few people other than US EPA and DOE officials, and appliance company experts, can really understand it. So rather than look at the standard let's look at a couple of examples.

An ENERGY STAR rated, 10 cubic foot, auto defrost unit that uses 309 kwh/year, is 21% better than the minimum required for its category.

A 14 cubic foot partially automatic defrost unit that consumes 254 kilowatt hours per year, is a whopping 36% better than the standard specifies.

As you can see, even for fridges that sport an ENERGY STAR logo, there is a wide range of efficiencies, and remember that a big unit that exceeds the standard by 36% may still use more energy than a smaller fridge that exceeds the standard by only 20%, if the minimum standard for the two refrigerators differs. If you can downsize your fridge when you buy a new one, you will certainly save more electricity.

Once you have established how much energy your refrigerator uses (it should be somewhere between 400 and 600 kwh/year, depending on the size of unit, or even more if you have wasteful features such as side-by-side doors or an exterior ice and cold water dispenser) you can compare the energy use of your unit to those at the ENERGY STAR website, and see if it's time to do a refrigerator tune up, or replace your refrigerator altogether.

If you're lucky, you may discover that the model you have now is already an energy saving refrigerator. If not, at least you'll have a great tool for checking whether your new fridge measures up to its efficiency rating.