A funny thing has happened as we’ve loaded up our homes with flat-screen TVs, game consoles and wireless speakers—our homes have actually become more energy-efficient. While we may have many more devices now, energy use by everything from refrigerators to cable boxes has dropped considerably over the last decade. The reductions might not be enough to rethink panel-size recommendations, but they underscore the importance of energy standards in the face of efforts to reduce overall energy use.
You might have heard some of these statistics over the last few years, because a couple of them made headlines. Most notably, between 2010 and 2017, total U.S. residential electricity sales dropped by 3 percent, and per capita sales fell 7 percent over that period. In addition, that period included a major economic recovery. Economists claimed we had managed to break the longstanding link between economic growth and energy consumption.
While 2018 saw an uptick in residential energy demand, that year also had a particularly hot summer, and air conditioning is the biggest contributor to how quickly a home’s electric meter spins. Jennifer Amann, building program director for the American Council for an Energy-Efficient Economy (ACEEE), believes the flat-to-downward curve seen between 2007 and 2017 is likely to continue. She sees the changing demand pattern becoming more pronounced as the impact of stronger building and appliance efficiency standards takes hold.
“I think the trend will be more for lower use as we continue to ratchet down electricity use in new homes, and more of the less-efficient appliances are removed from the building stock,” she said. “With things like building codes, it takes some time to see their results.”
David Roberts, manager of the Residential Buildings Research Group at the National Renewable Energy Laboratory, agreed with Amann’s assessment, noting particularly strong efficiency gains in home lighting and refrigeration.
“Also, we’ve seen some pretty significant gains in miscellaneous electrical loads,” he said, noting, for example, a broad move away from desktop computers to more efficient laptops. “We keep adding those things to our homes, but they keep getting more efficient.”
The refrigerator is an excellent example of how efficiency standards have pushed manufacturers toward innovations that might not otherwise have made it to market. In 1974, according to the ACEEE, the average refrigerator used more than 1,800 kilowatt-hours per year, making it the “most energy-thirsty appliance in the family home,” in the words of the California Energy Commission (CEC). In 1976, the CEC set efficiency standards for all refrigerators sold in the state, a move that led to the first national standards in 1987.
Multiple rounds of standards since then have significantly reduced refrigerator energy demand. The current national standard took effect in 2014 and has made today’s products more efficient than ever. An April 2019 Consumer Reports feature on refrigerator efficiency notes that a 2015 model their lab tested side-by-side was 17 percent more efficient than a similar version tested in 2009. And this energy reduction has occurred even as refrigerators have gotten noticeably larger.
In today’s homes, air conditioning now accounts for the greatest share of the monthly electric bill, though this equipment, too, is getting more efficient. Energy performance for air conditioners—including window units, central air condensers and both air-source and ground-source heat pumps—is quantified in the seasonal energy efficiency ratio (SEER), which represents the cooling output over a cooling season, divided by its energy consumption in watt-hours. Under current standards, new air conditioners must have a SEER rating of at least 13 or 14, depending on location. The most efficient units can have ratings of 21 or higher.
Split systems, with an outdoor condenser unit connected by refrigerant tubing to an evaporator coil indoors, are the most common type of central air conditioning equipment now cooling U.S. homes. Several factors contribute to their improved performance, Roberts said.
“One is the size—air conditioners with higher SEER ratings have larger condensers. And then, multispeed and variable-speed condensers can save a lot of electricity. They tend to operate more efficiently at part load,” he said.
Of course, such central air conditioning systems require ductwork to circulate cool air through a house. On the other hand, ductless mini-split systems offer higher SEER ratings than standard designs—up to 30.5 for the most efficient units. But this efficiency comes with a couple drawbacks. First, the systems require wall space for mounting interior air-distribution units, and second, they’re also more expensive than ducted equipment—up to 30 percent more, according to U.S. Department of Energy figures.
After air conditioning, water heaters usually are a home’s second-biggest electrical load. With standard tank designs, there isn’t much more that can be done to boost their performance beyond just adding more insulation to the tank wall, Roberts said. The resistive heating element is 100 percent efficient, he said, meaning 100 percent of the electricity it uses is transferred into heat. However, efficiency declines as heat transfers out of the tank before the water inside the tank can flow to our showers and dishwashers.
Looking beyond the standard tank unit, though, a number of other approaches use much less electricity to supply hot water. The newest of these are heat pump models that draw warmth from the air surrounding the equipment. This makes these water heaters less efficient in cooler climates but possibly a good solution in the South and Southwest, according to Roberts.
“They’re twice as efficient out of the box, but their actual performance can vary,” he said. “The cooler the space around them, the less efficient they are. They’re great in California and Arizona garages and a little less ideal in more northern areas.”
Clothes dryers round out the list of home appliances with the largest energy demands, but Amman said newer units boast advanced technology to ensure they don’t run any longer than needed.
“The best thing is the use of more sophisticated sensors and controls—moisture sensors in the drum and exhaust—so they can shut off power to the dryer as soon as the clothes are dry,” Amman said. “As clothes washers have been getting more efficient, the clothes come out much drier.”
While lighting has never been a home’s largest electrical load, it has lately become significantly smaller with the introduction—and rapidly falling cost—of LED lamps and fixtures. What was almost a novelty lighting technology even five or six years ago has now surpassed the compact fluorescent lamps (CFLs) that used to represent peak lighting efficiency. An 8- or 9W LED lamp now can produce equivalent illumination of a 60W incandescent—multiply that 51W reduction by the average number of fixtures in a home, and you’ll see a large drop in monthly electricity demand as a result.
“Shipments of LEDs have almost wiped out CFLs,” Amman said. “Some of the major manufacturers don’t even produce CFLs anymore.”
The Trump administration has proposed rolling back standards that are set to force an efficiency standard of 45 lumens per watt by 2020 for a number of specialty lamps, including the reflector lamps used in many homes’ recessed lighting systems. While still-popular halogen incandescent lamps, which run at about 20 lumens per watt, meet current requirements, they would fall short under the 2020 target. Amman hopes the proposed rollback is rejected.
“The standards would really capture the fact the technology is ready,” she said, noting the ability of an 8W LED to match the output of a 43W halogen lamp. “The first step was a good step, but getting to the next step, to 8W, is a game changer. And now the price premium is very small compared to the halogen incandescents.”
With all these reductions in energy use across almost all home appliances and lighting systems, one might expect home electrical panel sizes to start getting smaller, as well. However, the 200-ampere (A) panel remains the standard choice for many electrical contractors, who see the number of devices and appliances growing in the home, even as most of them now require less power.
“I don’t see enough of a reduction to say, ‘I don’t use enough electricity, so I don’t need 200A service,” said Lewis Maffioli, president of Rockford, Ill.-based Wilson Electric Co. “I err on the high side, and there’s not that much difference in the pricing. You’re doing the same amount of work, but the wiring gets a little bigger and there’s an upcharge for a 200A panel [versus a 100A unit].”
Maffioli said his company focuses on higher-end residential projects that can come with some bells and whistles—or pools and hot tubs, in this case. In addition, some also have well pumps. Combined, these three loads, which could quite likely run simultaneously, could add up to 70A or more.
“If they say they’re never going to have a pool or a hot tub and all their appliances are going to be gas, then maybe we can talk about something smaller,” he said.
Roberts, it seems, would echo Maffioli’s advice on load sizing. Today’s most energy-efficient new homes often combine rooftop solar panels with an increasing dependence on electricity for heating and cooling, using heat pumps. Increasingly, those homeowners also will power their vehicles with electricity, so 30A or 40A charging equipment might be required. Electricity use, he believes, is only going to grow.
“There is, I think, going to continue to be efficiency gains, but there’s a drive to electrification of functions that have previously been fossil-fuel-fired,” he said. “So, while I think we’ll continue to see gains in efficiency, the overall residential-sector use is going to go up as we electrify the home and transportation.”