The Carlisle Mosquito Online

Friday, November 16, 2007


Every kilowatt counts:
my energy-conservation audit

If there was one certainty in my life, it was the fact that our NStar electric bill would always be using close to $300 monthly. I just could not accept the fact that we could be that much electricity every month. I was in denial and wondered if this energy dissipation could be related to a meter issue or faulty wiring.

Six months after we moved into our new home, we had had a meter issue and NStar replaced our old meter with a digital one. Even then the bills stayed the same. It was time to take some action to understand our true energy consumption. As painstaking as it may sound, I decided to run an audit of all things electrical in the house.

A friend of mine told me that the Gleason Public Library had a cool gadget called "Kill A Watt," an energy-usage monitor available for borrowing for a three-week period. The Friends of the Gleason Library bought four of the devices on the recommendation of the Carlisle Household Recycling Committee. According to Library Director Angela Mollet, "They have not stayed on the shelf since they first arrived on October 15 and they have already been circulated ten times. The comments received so far are very good." I decided to check out a Kill A Watt to accomplish my energy conservation effort.

Measuring kilowatt hours

The Kill A Watt monitor
Kill A Watt is a small, handy device with a standard three-prong AC plug on the back, ready to be plugged into the wall. When the appliance or device to be tested is plugged into the front socket, the unit will start to display kilowatt hours and powered duration time after the power is supplied. Electric consumption is displayed in kilowatt hours (KWH) from 0.01 to 9999. Counters will recycle to zero when they reach their maximum. To reset, just unplug the appliance from the unit momentarily. The one limitation is that only an appliance that can be plugged into a wall socket can be measured — the well pump and dishwasher, for example, are not eligible.

The first step in an energy consumption audit is to identify the appliances to be measured. My lists fell into the following categories:

· Always on — refrigerator, freezer (extra one), small refrigerator, two dehumidifiers, cable modem, printer

· Sometimes on — two TVs, two laptops, computer, printer, DVD player, toaster oven , microwave, washer, dryer, dishwasher, treadmill, bread machine, electric skillet

· Seasonally on — swimming pool pump, several room air conditioners, fans, electric heat (in basement only)

I entered all these categories and appliances into an Excel spreadsheet (a notebook will do as well) with the following columns: Device name, duration plugged in, KWH, and monthly cost. I then looked at my electric bill and calculated the NStar charges for kilowatt hours by adding the delivery figures that include distribution, transition, transmission, supplier cost, etc. (These are itemized on the monthly bill.) I concluded that the total charges for kilowatt hours were $0.17459.

Putting the Kill A Watt to work

Now it was time to put the Kill A Watt to work. The best way to measure energy consumption for the first category, the "always on," is to connect the appliance or device to Kill A Watt for 24 hours. I then noted the LCD display when the KWH button was pressed. Then I multiplied this by two factors — the number days in that particular month, and the per-KWH charge. Taking the freezer as an example, the KWH for 24-hour usage was 3.38. My monthly cost of the freezer was 3.38 x 30 x 0.17459 = $17.70.

The energy guzzler in this category was one of the dehumidifiers, which consumed a whopping 288 KWH per day, leading to a monthly cost of $50.28.

For the second category, the "sometimes on," I just plugged in the device for any cycle, estimated the average number of times a month I would use it, and arrived at an almost accurate monthly cost. The microwave, for example, which we barely use, showed a monthly expense of $2.

I was surprised to learn that almost every device that is plugged in, even when not in use, is drawing power, although at a minuscule level. When you total this usage over the course of a year, it could be a significant amount. This type of energy consumption is normally referred to as the "phantom load" and could contribute as much as 11% of your monthly electric bill. The best way to avoid it is to disconnect devices when they are not in use or use power strips that serve as a single point for turning multiple devices on and off. If you are opposed to frequent shutdowns and start-ups of your computer, you can set it to hibernate mode by accessing the control panel.

Coming up with a total

After I totalled the results of my audit, I compared them with my NStar bill for that month; our KWH usage almost matched our average monthly bill. I did have to add some ball-park figures for lighting and devices like the well pump which could not be measured with the Kill A Watt.

CFL Bulb
As part of my energy conservation effort, I looked carefully at all our appliances and devices to see which ones we could do without. Here are some of the measures we have taken so far:

· Eliminated the use of one of the two dehumidifiers — a monthly saving of $50.

· Turned off the basement freezer — a barely used luxury which was costing about $20 a month.

·Turned off the second small refrigerator, a monthly saving of about $15.

· Switched to compact fluorescent light bulbs (CFL).

· Stopped using the dishwasher's dry cycle.

· Replaced the manual thermostat in the basement with an electronic programmable thermostat.

· Unplugged devices when not in use. Based on industry statistics, this should reduce my bill by $20.

The next logical step for us is to shop for energy-efficient appliances. High on the list of replacements is the dehumidifier. When our appliances reach the end of their projected life, we will look for the energy-star rating: the greater the number of stars, the less the energy consumption.

The energy consumption audit taught me a new meaning to the saying, "Every kilowatt hour counts."

2007 The Carlisle Mosquito