How much energy does my refrigerator consume? Ways to find out

Before you run out and purchase a new energy efficient fridge, it's important to know how much electricity your current fridge consumes. Why? Here are three reasons.

First, because you'll be looking at Energy Guide labels on the new fridges, to determine which ones will be the cheapest to own, and you might as well have an idea of how they compare to your current fridge.

Second, if you plan to replace your fridge mainly to save electricity, you might find that you don't need to. Although today's fridges are much more efficient than those of a decade back, your refrigerator may turn out to be efficient enough that there isn't a compelling motivation to replace it. 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 refrigerator is using so much energy, that a refrigerator tune-up will save you electricity even in the short time before you get the new model. Tips that can really help include: checking the door gaskets for leaks or cracks, checking the temperature in both compartments (38-40F for refrigerator, 5F for freezer), ensuring the compressor and coils are dust free; and ensuring good airflow around the unit. Even if you discover that your old fridge is an energy guzzler and you do a tune-up, you may discover that the tune-up on its own will mean big electricity savings.

Your existing refrigerator could conceivably be costing you $25 to $125 a year more than it needs to, and your new fridge may turn out to be less efficient than its ENERGY STAR label claims, depending on how you use it. But if you merely assume that a refrigerator consumes what its label says, you'll be leaving a lot of savings on the table.

What if I told you that a $25 investment could save you at least $40 a year, every year? It turns out that there is a cheap device that can do just what we want: measure the electricity consumption of your fridge.

I got a Kill A Watt meter around five years ago and have used it to measure the energy consumption of many appliances in my house. I have also lent it to many others so they could uncover electricity savings in their homes. These meters are available for around $20 and they tell you how many kilowatt hours per day (kwh/day) an appliance like a fridge consumes. A measurement takes about three days, because a fridge cycles on and off, and only a longer measurement irons out the peaks and valleys of the fridge's electrical use. But once you have that measurement, you will know what your refrigerator uses and you can start planning actions to save electricity, or you will be able to make a better decision about replacing your existing fridge.

The Kill A Watt meter measures electricity consumption in a number of ways. The key readings for our discussion are time elapsed and kilowatt hours consumed. The meter starts measuring both of these values from the moment it is plugged in, so if you plug in the Kill A Watt meter, then plug your fridge into that immediately, you'll start to see how much energy your refrigerator churns through once at least 24 hours have passed. Follow these steps:

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

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

3. Push the refrigerator back. (You can just stick the meter between the wall outlet and the refrigerator, if that enables you to see the meter 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 other metrics, the time 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 consumption would be 2.37 / ((34/24)+(22/1440)), or 1.655 kwh/day. Don't wait longer than 96 hours to do your final reading, because the time elapsed measurement wraps to zero at 99h59m.

Most fridges are rated based on kwh consumed per year, so to compare your old refrigerator with what's for sale now, you can multiply the kwh/day value by 365. Our example refrigerator getting 1.655 kwh/day uses 604 kwh/year. A 16 cubic foot Sun Frost refrigerator, in contrast - one of the most efficient fridges on the market - consumes only 254 kwh/year.

You can see how your existing fridge stacks up against new models by looking in the www.energystar.gov refrigerators database, for models that are similar to your fridge. Refrigerator efficiency standards have risen in the last few years, and a fridge typically consumes more electricity as it gets older, because of hardening 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 minimum standard, so if you own an old refrigerator that was not ENERGY STAR rated to start with, you can see there is a big opportunity to cut energy use, especially if you know what the old fridge uses.

The efficiency requirement for fridges varies based on type (top or bottom freezer, side-by-side, or no freezer), volume, auto-defrost capabilities, and coolant type. And the formula is so convoluted that few people other than US EPA and DOE officials, and appliance company insiders, can really grasp it. So rather than quote the standard let's look at some examples.

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

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

As you can see, even for units that have an ENERGY STAR label, there is a big range of efficiencies, and remember that a large unit that exceeds the standard by 36% may still consume more energy than a smaller refrigerator that exceeds the standard by only 20%, if the minimum required standard for the two refrigerators is different. If you can downsize your refrigerator when you buy a new one, you will certainly save more money.

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

If you're in luck, you might discover that the model you have now is already an energy efficient refrigerator. If not, at least you'll have a great tool for seeing if your new refrigerator measures up to its efficiency rating.