How to Stop the Energy Vampires

When we moved into our new house (new for us, at least), we were excited. But that excitement waned a bit when we saw our first power bill. We weren’t too happy about the thought of paying over $100 a month for electricity in our small space—1,500 square feet, two floors, and two permanent occupants, excluding somewhat frequent guests. In addition, we had always thought of ourselves as conservationists. But having our usage rated several tiers higher than the minimum by our provider, PG&E, made us feel like we should be doing more. The way our (and we think most other peoples’) power bill works is that when your usage exceeds a utility-defined lowest tier, any additional energy you use is charged at a higher rate. Typically, there are several tiers, and the rates increase substantially as you pass from one to the next. Because of this, you can sometimes cut your power bill significantly by cutting only the power you use that falls in the top tier. For example, it is often possible to cut your bill in half by cutting your usage by a lot less than half.

We, therefore, embarked on a mission to get our power usage within the lowest tier, as defined by our power company. To this end, we made some immediate changes that have been discussed many times by many other people, such as replacing all our incandescent lightbulbs with CFLs or LEDs. This approach made a major difference in our total monthly consumption, but we wanted to know more about where our electricity was going.

We ended up using mostly two tools: the Belkin Conserve Insight energy use monitor and the smart meter the power-company installed outside our house.

Measuring Plug Load

The Belkin Conserve Insight is a very simple device that you plug into your wall and into which you plug an appliance whose power usage you want to monitor.

Lightbulbs have gotten a lot of attention in terms of potential power savings for homes. This is for good reason; you can save a lot of money replacing an incandescent bulb with an LED or CFL bulb. It is easy to figure out how much power any lightbulb in your home draws. It is usually written on the box or on the bulb itself. You can verify these values by plugging the lightbulb into a lamp and the lamp into the Conserve. For the most part, this exercise is a waste of time, because bulbs are labeled very accurately. We found at most a couple tenths of a watt of difference between the rated power use for a CFL bulb and the measured value. However, many homes have dimmer switches that allow you to dim bulbs in fixtures. We have a few LED bulbs in such fixtures that we leave on 24/7 or nearly 24/7. To estimate the power use of this situation, you can use the Conserve in conjunction with a lamp and an external dimmer switch. You plug the dimmer switch into the Conserve, and plug your lamp into the switch, and dim the switch to measure the power used at various brightness levels.

While not every device in your home that uses power can be plugged into the Conserve, a surprising number of your devices can be. And a surprising number of these devices use power 24/7, when plugged in, even when you might consider them to be in an off state. Examples include your microwave and your garage door opener. This is what is commonly known as a standby, or “vampire” power draw. Other devices, such as the modem and wireless router, we leave on and operating 24/7, and so they draw power continuously.

While it is important to minimize standby power usage, that isn’t the whole story. After making some changes (which you can read about down below), standby usage accounted for about one-quarter of the total power usage at our house. For devices like our TV and fridge, active power usage (power draw when the device is on, or active) accounts for most of the total power draw. We discovered this by leaving these devices plugged into the Conserve for several weeks to get our average power usage. For example, we determined that our fridge consumes on average 60 watts based on our usage patterns, whereas the idle power draw was only 4.9 watts. In general, our fridge and our electric clothes dryer are the two biggest consumers of power at our house (each using 40–50 kWh per month, depending on exact use and climate).

Using Your Smart Meter and Circuit Breaker to Measure Everything Else

The Conserve works great to measure everything that can be plugged into a standard outlet, and as we mentioned above, that’s more things than you might think. However, at our house, we discovered that even if we were to unplug every possible device and turn off all the lights, we were still using about 29 watts of power 24/7. How on earth were we still using 29 watts?

We went around our house attempting to discover things that were using power but were not plugged into an outlet. A few candidates came to mind immediately. For example, our home has a street number that is lighted 24/7, and we also suspected that our furnace might be drawing significant standby power. However, it turned out that there was a lot more going on than just these two devices.

In order to discover where the 29 mystery watts were being used, we took the following approach. We discovered that our utility-installed power meter reports the current usage in our home, in real time, to the nearest watt. Thus, we didn’t need to use or install any third-party device to get this information. This allowed us to turn on and off power to certain rooms, or to different circuits on our circuit breaker and see what difference that made to our power usage as reported in real time by the smart power meter. (To avoid a lot of running back and forth, make this a two-person job.)

We found that the best way to measure power was to measure differences in the meter readings. To this end, we prepared a control room in our house, corresponding to a single circuit breaker that used a very constant 20 watts of power from which we can measure the power difference of turning on additional breakers. We determined the control room usage by taking measurements with the Conserve and confirming these measurements with an initial power meter reading. We would then turn off all the breakers except the one dedicated to the control room and the breakers that controlled the rooms/circuits containing the devices whose power we wanted to measure by reading the meter. In this way, we were able to isolate and measure the power usage on all the different circuits in our house to within +/- 0.5 watts. For example, in our home the furnace is controlled by its own breaker, so we were able to determine that its 24/7 standby power use was 8 +/- 0.5 watts. Similarly, all of the smoke detectors in our home are isolated on a single breaker, and we were able to determine that their standby power use was about 2.75 watts.

We ended up discovering a list of other devices (some completely unexpected) that were using power. In some cases, the same device (like a ground fault interrupter outlet) appears on multiple circuits, and, in some cases, a single breaker controls several nonpluggable devices—for example a GFI outlet and a timer switch. You can solve for unknowns x, y, z by setting up multiple equations (one for each breaker), in order to determine how much power each of the devices uses. That’s how we ultimately discovered the origin of the missing 29 watts.

How We Minimized Standby Usage

Now that we had figured out where all the power was being used in our house, we started trying to reduce our consumption. A key requirement was that we not lose any functionality—at least not any functionality that we actually use.

As mentioned above, a major way to save power in the home is to replace incandescent light-bulbs with CFL and LED bulbs. While these lead to major savings, there can be some caveats. If you are into home-automation (like we are), “smart” lightbulbs that connect to your Ethernet either through WiFi or Bluetooth to a hub are a must have. But, this functionality may mean that your bulbs are using power 24/7. For Phillips hue bulbs, we measure this to be about 0.3 watts. Other brands may use significantly more.

One of the first things we did was to put our power-hungry digital video recorder on a timer. This is a homebrew home theater PC that we could safely shut down using a Linux task scheduler before cutting the power with the timer. There was no need for the device to be on from midnight until 9 am and other times when we are not home and are not interested in recording any TV shows. Since this device uses about 40 watts when on (and close to 4 watts when off but still plugged into a live outlet), cutting down the time when it receives power leads to big savings.

We added another product from the Conserve line, the smart power strip, to our media center setup. What is “smart” about this strip, and other strips like it, is that you can cut the power entirely from peripheral devices when a control device is turned off. In our case, we use the TV as the control device. When the TV is turned on, our subwoofer, Wii, and a couple other peripheral devices are powered on. When the TV is turned off, all power is cut from these devices. It works great and is no less convenient than before. In this way, we pay only the 24/7 standby power costs of the TV and the strip itself (which is approximately 0.3 watts) instead of the standby power of all of these devices (which for the subwoofer, in particular, is quite high). Similarly, in our office, we added a power strip with an on-off remote control that is capable of cutting and restoring power to our computer, printer, and other peripheral devices. The remote can be mounted on the wall and actually makes turning on the computer more convenient.

In some areas of our house, we had GFI outlets in places where we never intended to plug anything in. For these cases, we now save power by simply turning off the breaker on the circuit containing the GFI. This can also be done for the furnace breaker in the summer, when we have no intention of turning on the heat. This alone saves 8 watts of power usage for most of the year. Other devices, like the cable subscription amplifier, we discovered could be simply unplugged without negative effects (since we don’t have cable). In addition, we replaced our lighted doorbell button with an unlighted button.

Saving a few watts here and there may seem trivial, but savings of 1 watt over the course of the year amount to about 8.8 kWh hours of energy use. For us, even at the lowest tiered rate, that is about $1.50. And if you are going above the first tier, the rate is much higher.

With these optimizations, we can practically reduce our 24/7 standby power draw (including devices like the modem and router intentionally left on 24/7) to about 60 watts. It would be difficult to further reduce usage without taking significant hits to functionality and usability, or making a major investment in new appliances (like a new microwave that doesn’t constantly consume 6 watts of power!). Adding a switch to the microwave would be problematic, because the microwave can draw over 15 amps and because the flashing clock face would be annoying and would need to be reset after losing power. At the end of the day, by replacing our lightbulbs and making the other changes discussed above, we’ve reduced our power bill by approximately two-thirds.

Is it crazy to determine to a fraction of a watt where all the power in your home is being used? Sure it is. But if you are data nerds like we are, it empowers you to really control your home. And for us, that’s the difference between owning a home and just living there.