Builder-Installed Electrical Loads
Parts of the House That Stay On
Not too many years ago, when you unplugged all the appliances in a home the doorbell transformer was the only device still drawing power. That’s no longer true—a host of devices now draw power before anybody moves in. The most common devices include ground fault circuit interrupters (GFCIs), garage door openers, and hardwired smoke alarms.
We call this family of products builder-installed electrical loads, because the builder typically installs them to comply with health and safety codes or because most customers want them. Since these devices are permanently installed and are not controllable by the occupants, they create an electricity “mortgage” for the life of the home. Our investigations have shown that these loads add up to a significant amount of energy. Not huge, but worth further investigation.
Table 1a. Required
Table 1b. Installed to Provide
|Entryway audio and video systems|
|Garage door openers|
|DC exterior-lighting power supplies|
|Street address lights|
Table 1c. Heating, Cooling,
|Gas demand water heater controls|
|Furnace/air handler controls|
|Instant hot-water dispensers|
|Mechanical ventilation fans|
|Heat pump crankcase heaters|
|Minisplit air conditioners|
|Ceiling fan remote controls|
|Hot-water recirculation pumps|
|Boiler circulation pumps|
|Motion-activated faucet sensors|
Table 1d. Communications
Table 1e. Other Amenities
|Vacuum cleaners (built in)|
|Gas fireplace controls|
|Remote-controlled blinds and curtains|
|Smart toilets (“washlets”)|
|Heated towel racks|
|Inverters for PV systems|
What Are Builder-Installed Loads?
Builders install electrical components, equipment, and appliances. The most visible are kitchen appliances like ranges, microwave ovens, and dishwashers. But builders also install less visible devices that are
- required by building codes (such as life safety equipment);
- expected by buyers (such as remote-controlled garage door openers); or
- selected by the builder to make the home more attractive to buyers (such as a video doorbell).
Those devices draw power, or loads. Builder-installed loads are the electricity use of all devices installed in a home by the builder that are not occupant controllable. This is not a perfect definition, but it is relatively constant and is an easily measured value regardless of how the house is occupied or used. A large or complicated house can easily have 30 separate builder-installed loads. A list of common (and not-so-common) devices is shown in Table 1. We divided them into five categories: safety, security, HVAC, communications, and other amenities and features. Nearly all of these devices draw power continuously, even though many have mechanisms to control the desired features.
The variety and number of builder-installed devices is growing steadily (and we invite readers to alert us to new ones). More and more, builders are installing the infrastructure needed to support the Internet of Things. And each device connected to the Internet of Things draws a little power.
Altogether, How Much Energy?
Before we answer that question, it’s important to understand how we arrived at the answer. Many of the builder-installed devices have several operating modes, and their energy consumption depends on how the occupants operate them. For example, a demand-style water heater burns gas to heat the water but also draws power to operate the controls. We focused on the devices’ continuous power consumption, which is usually called the standby or idle power consumption. Occupants cannot switch off this power (or at least it would be difficult or would create an unsafe situation). We attacked the energy question in two ways—from the top and from the bottom. First, we measured a home’s total builder-installed load. We developed a measurement method—which we describe below—and then applied it to some California homes. We also measured individual appliances and then tried to estimate the total load based on a survey of the devices. Each approach contributes insights into the size and composition of builder-installed loads.
Whole-House Measurements of Builder-Installed Loads
We developed a method to measure the total electricity usage of builder-installed loads in a home. This method assumes that the house has a smart meter—a reasonable assumption for about half of the nation’s homes—and makes possible the measurement of the whole-house load without additional equipment. (The test method could also use a spinning disk meter so that nearly all homes could be measured.)
The whole-house test consists of two steps: (1) placing all of the home’s equipment in a builder-installed state, and (2) measuring the energy consumption with the house’s kWh meter. The key goal is to reliably and consistently place all of the builder-installed equipment in its builder-installed operating state, with no devices operating in active mode. This can be a tedious operation, because each device must be configured into a mode that represents the user noncontrollable state. For example, all lighting is turned off and the HVAC system is energized but is placed in off mode with the fan switched off. The water heater is left on but with a lowered set point and with no water draws occurring during the tests. In addition, all intermittent or cycling devices must be unplugged or disconnected at the breaker so that they do not enter an active mode during the measurement. Of course, all nonbuilder-installed devices must be unplugged. Defining the test states for each device can be difficult. In general, we sought each device’s lowest plugged-in state. Some products have start-up or reboot programs, so they do not stabilize at the lowest power draw for some time. The original settings must be carefully documented so that you can return them to those settings at the end of the test. (This is important!)
Once the house is in its builder-installed state, the power is measured using the house’s kWh meter. Most smart meters periodically display the home’s total power consumption in kW or watts. We recorded the total power three times, spaced three minutes apart. If the readings varied by more than 5 watts, the house was checked again for intermittent or active loads. If the readings were consistent, the average value was recorded as the whole-house load.
Some devices, such as those with intermittent loads, can make measurement difficult. These include temperature-controlled equipment, such as crankcase heaters, attic ventilation fans, and instant hot-water dispensers. Other devices can cycle; these include water softeners and devices with rechargeable batteries, such as security systems. Instant hot-water dispensers illustrate the potential ambiguity of certain settings. The user-controlled energy use would be that required to provide the hot water supplied, while the noncontrolled energy use would be that required to maintain the storage tank at the desired temperature (that is, the standby energy). Neither of these values is easily measured using the house meter, so we recommend that they be excluded from the whole-building measurement and then added later using a calculation.
Field measurements must be collected in the brief window of time after most of the finish work has been completed but before the house has been sold. If the data are collected too early, it is possible that electrical circuits are still being wired, and equipment is still being installed or has not yet been energized. On the other hand, if the data are collected too late, it may not be possible to gain access to the home, or additional occupant-owned equipment may already have been installed. In addition, the builder must be amenable to allowing access to the home during the most hectic stages of construction. It is also possible to test existing homes; there the best time is at the time of sale, after the original occupants have left but before the new ones have moved in.
Results from 17 Homes
We measured the total builder-installed loads in 17 new California homes (see Figure 1). Floor area varied from 1,800 to 5,000 square feet, which means that these houses were larger than average. We identified an average of 34 builder-installed device loads in each home. The average load was 128 watts, but loads ranged from 70 to 260 watts. A continuous 128W load corresponds to an annual consumption of 1,100 kWh per year. In California, that 1,100 kWh corresponds to almost 15% of an average customer’s electricity use. Alternatively, 1,100 kWh corresponds to the electricity consumption of two modern refrigerators or a significant fraction of the electricity generated by a typical rooftop PV installation. All this occurs before the house is occupied!
These measurements suggest that builder-installed loads are a surprisingly large use of electricity in new homes. Furthermore, they have escaped the notice of energy efficiency researchers, regulators, and policy makers.
But which devices are the biggest culprits? To answer this question, we measured a variety of individual products. These measurements are sometimes challenging, because the devices are often hardwired into the home’s circuits.
Testing Individual Builder-Installed Devices
We tested devices in the laboratory and in the field. We created a test rig to safely and reliably hold each product under test. A test rig was needed because hardwired devices lack conventional plugs. We then measured the power consumption of each device using a procedure similar to the international method for measuring standby power, International Electrotechnical Commission (IEC)-62301. We set the device to operate in its lowest possible power mode (other than unplugged) and sampled the device’s power consumption every second for ten minutes. The energy use was calculated as the average power over the last five minutes (with the first five minutes used as warm-up). We also verified that the power use was stable by requiring a deviation of less than 1%. The power consumptions of most of the devices were below 1 watt, so an extremely sensitive meter is required to obtain accurate results.
Table 2. Power Use of Life-Safety Devices
|Device Category||N||Mean Power (Watts)||Minimum Power (Watts)||Maximum Power (Watts)|
A few devices drew much more than a few watts. For example, mechanical ventilation fans in the homes we measured drew 40–60 watts. Radon fans probably draw a similar amount (but these are rare in California). Codes require both to operate continuously. Heat pumps have crankcase heaters that draw a minimum of 30 watts. Hot-water recirculation pumps—which are becoming increasingly common—have been measured at 50 watts, though those with demand controls may draw less than 3 watts.
Life-safety devices illustrate perhaps the most intriguing aspect of builder-installed loads. We measured the power draws of 35 life-safety devices that are required by code, including smoke alarms, CO alarms, GFCI outlets and breakers, arc fault circuit interrupter (AFCI) outlets and breakers, and various combination devices. The power use of these devices is summarized in Table 2.
These devices draw very little power, rarely over 1 watt. But there are about 20 of these devices in the average new home. Note that the maximum power use within each category can be as much as 5 times the minimum power use, indicating that there is ample room for improvement. We measured only a few models, so there may be worse units. Together they add up to a nontrivial continuous electrical load.
Furthermore, updated building codes require more and more life-safety devices in new homes (because they save lives!). GFCIs now appear in kitchens, bathrooms, garages, and other rooms where standing water might be present. Smoke alarm requirements are growing, too. Figure 2 shows how the types and numbers of life-safety devices have increased over time.
Growth of Life-Safety Devices
Reducing Builder-Installed Loads
Can builder-installed loads be reduced? Yes, but it’s not easy. Installing only the most efficient devices can make a large difference. Our measurements of GFCIs and other devices showed that similar components often had widely different consumptions. Unfortunately, manufacturers don’t offer information about their products’ power consumption, and builders don’t have the watt meters (or the time) to make these measurements. Nevertheless, here are a few suggestions:
Buy the best possible ventilation fans. These are often the largest contributors to a home’s builder-installed loads. The most efficient, Energy Star units draw less than half the power of the worst. They are also typically the quietest (which alone is sufficient reason to select them).
Rainer, Leo, Aditya Khandekar, and Alan Meier. “Builder Installed Electric Loads: The Energy Mortgage on a New House.” In Proceedings of the ACEEE 2018 Summer Study on Energy Efficiency in Buildings, Pacific Grove, California: American Council for an Energy-Efficient Economy (Washington, D.C.), 2018.
Meier, Alan, and Quentin Alliot. “Permanent Electrical Loads in New Homes.” In Proceedings of the ACEEE 2016 Summer Study on Energy Efficiency in Buildings, Pacific Grove, California: American Council for an Energy-Efficient Economy (Washington, D.C.), 2016.
Delforge, Pierre, Lisa Schmidt, and Steve Schmidt. Home Idle Load: Devices Wasting Huge Amounts of Electricity When Not in Active Use. NRDC Issue Paper IP:15-03-A. San Francisco: Natural Resources Defense Council.
The authors thank the California Energy Commission’s EPIC program for supporting this research.
When installing outlets, try to daisy-chain the GFCIs. This way many outlets can share the same circuit. The drawbacks are longer installation time and perhaps more wire. Be sure to label the outlets so occupants know that they are protected.
Control that hot-water recirculation pump. Install demand controls to regulate the times that water is actually recirculated.
Attach as many builder-installed devices to controllable outlets as possible; if they aren’t needed, switch them off. Some devices, such as hot-water recirculation pumps, can be switched off during vacations or certain seasons. Here too, labels are important.
It’s also important to perform the whole-house measurements of builder-installed loads. These measurements aren’t difficult and can alert you to an anomalous high consumption that can be repaired before it becomes part of the home’s energy mortgage.
Builder-installed loads will likely grow because of two trends. First, the life-safety codes will require more devices. This is a good thing, especially if a few more watts saves a life. Second, Silicon Valley and the electronics industry continue to dream up new, irresistible applications of the Internet of Things in the home. A decade ago, nobody even imagined that a gadget named Alexa would be listening for instructions in millions of American homes. Yet soon Alexa and her friends will move from novel to necessary, and after that become just another builder-installed device. Wi-Fi routers are even further along this trajectory; indeed, some modern homes can’t function without them to connect door locks, security systems, and Internet-connected thermostats. A final example is the toilet, which is being rapidly transformed from a dumb plumbing fixture to a complex electronic device (drawing several watts continuously). We can hardly wait.
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