Zero-energy buildings: We have the technology


Earlier this week, I talked to Kent Peterson, past president of the American Society of Heating, Refrigerating and Air Conditioning Engineers. This was a lot more exciting that it may sound. ASHRAE standards on energy efficiency end up written into our building codes, which means the organization plays a big role in influencing the shape of energy policy in this country. I talked to Peterson to find out whether zero net energy buildings—buildings that produce as much (or more) energy as they use—were really a practical goal. His answer might surprise you.

"We have studies that show [zero-energy buildings] are practical for approximately 62% of buildings in the U.S., based on technologies we have today," he said. "That's mostly one and two-story buildings and still leaves out a lot that can't reach it, but those buildings can be low energy.

In fact, Peterson said that currently available energy efficiency technologies alone (not even looking at generating power from wind or solar sources) could reduce the amount of energy used by the total U.S. building stock by 50%.

The catch: Hitting that 50% energy reduction goal—let alone getting to zero-energy buildings—means more than buying a better boiler. The environmental systems in buildings—the lighting, heating, cooling, etc—are already pretty efficient, Peterson says. When your heating system is 80% efficient, you can't get a 50% reduction in overall energy use by focusing on squeezing out the last few drops there. Instead, Peterson says we have to put more thought into reducing "plug load"—a fancy way of talking about all the gadgets and appliances we plug into sockets.

Think of all the stuff you leave plugged in all day. Like the microwave. It's nice having that clock function, and it really doesn't take much energy to run. But over the course of a year, all the electricity you used to run that microwave clock ends up being enough to power 30 hours of microwave cooking time, Peterson says. All the little "phantom" draws add up, and they bite us hard.

Automation is the muzzle. I've gotten pretty good about remembering to shut lights off in rooms nobody's using, but expecting me (and millions of Americans like me) to thoughtfully and correctly power down every electronic device they aren't using even half the time is about as unrealistic as expecting Anna Karenina to become the movie blockbuster of the summer. Instead, we can rely on "set it and forget it" systems that turn off unused devices while we're at work or asleep based on timers or occupancy sensors. Peterson already has something like this in his house.

"It's just controlled by my computer in my house, and it cuts power to specific outlets either by timer or click of a button. So I can cut power to my TV overnight, and automatically reduce phantom loads. That system had a bigger impact on my home energy use than all my other energy saving projects combined."

Image courtesy Flickr user Rennett Stowe, via CC


  1. Want to disconnect your appliances from the grid without having to unplug them every time? Wall sockets built with switches. You switch on the socket when you want to use the toaster, you switch it off when you’re done.

    Lots of places outside the US have this standard, I don’t know why we don’t. I know it’s a hassle to unplug things and deal with the loose cords and whatnot, but I’d love to be able to cut power to a plugged in appliance with just the flip of a switch.

    Also? Automated lighting. People leave lights on ALL THE TIME. Motion sensitive lights would help tons. If a room is empty, the lights switch off.

    Heck, there’s also the matter of sheer light pollution and waste. There are countless unnecessary lights all over cities, suburbs, everywhere, which run all night and throw hours and hours of electricity away by flooding the sky with light pollution. Multiply the cost of one such light by millions and it adds up quickly.

    ~D. Walker

  2. Yes, this is great- please, more info-

    also, this is off topic, but if anyone knows more about how to build a battery-run car, I would LOVE to do this instead of buying a new/used car. But I have no idea how and I realize this isn’t a little science project. Are there groups or resources out there that will help you build one? Anyone have any ideas?

  3. X10 controls has some methods.
    Many of the plug loads are barely affected by turning them off. For instance, your DVR off button basically turns off the LED indicator, and still draws nearly the same energy on or off.
    Lawrence Berkeley Labs has a good resource that addresses the standby issues.

  4. @tboot – well, we do it with a power strip. This works, but it might not work as well with our TV, Dish receiver, and DVD recorder that insist on having their clocks reset when I do this by flashing “12:00” until I get annoyed enough to just do it. Such devices should have their always-on stuff run from coin batteries (which cost less than a buck apiece and run for years), which in turn must be easily accessible. In fact, it should be a requirement to get that coveted Energy Star rating. I just can’t see that much power being required to run a clock on everything I own.

    1. “it should be a requirement to get that coveted Energy Star rating.”

      That is a great idea! I’m willing to bet corporate interest would block it, unfortunately.

      Props to all the people on here who have taken matters into their own hands.

  5. That clock in the microwave oven is not a very good example, since it represents about 0.2% of my total electric bill. We won’t get there by knocking off a few parts per thousand, as the author himself states when discussing efficiency of environmental systems.

    Let’s work on the big steady loads before dealing with the small steady loads.

  6. I bet this wasn’t conceived to work in Atlanta, where air conditioning is effectively life support.

  7. unplugging stuff or hitting the button on a power strip is not that unrealistic or hard to do. goddamn people are lazy.

  8. You can control an outlet with a computer by either using Insteon outlets or relays. X10 works. I use it currently, but will be upgrading to Insteon as they are compatible.

    The biggest problem with homes are the designs of the houses themselves. The HVAC system might be 80% efficient but that is the unit not including leakage from the house. We could make the houses themselves far more efficient by adopting different building practices. The insulation envelope must be continuous without floor plate breaks. Also, if there is a large thermal mass within the insulated space it can act as a flywheel making the HVAC work less often. Also, it always makes me laugh when someone thinks they are sooo green because they have gigantic south facing windows without any overhang that are low-e insulated glass in L.A. Yeah that’s way better than no window and r-30 insulation.

  9. My entire home is automated…all appliances and lights are controlled by computer. No vampire devices…no lights left on. I recently switched to LED bulbs on the lights I use the most. One fixture went from 250 WATTS to 20.

    Also…all regular bulbs have a default setting on the switch to about 40-60% of full brightness.

    It works.

  10. We are currently building a super-efficient house and one thing we are doing is putting outlets that have TVs, computers, microwaves, etc, on wall switches. Much easier and more convenient than power strips.

    1. An easier way to do that is to put them on Insteon wall plugs so that you can have one live plug and one controlled plug. You can then turn them off from any Insteon wall switch or handheld remote. This also saves you from wiring things to switches.

  11. “It’s just controlled by my computer in my house, and it cuts power to specific outlets either by timer or click of a button. So I can cut power to my TV overnight, and automatically reduce phantom loads.”

    Uh…how much energy does the computer being on all the time draw vs. the TV, etc. in standby mode?

    The clock issue is (I think) going away as more and more devices like TVs/DVRs/etc. automatically set their time. But the whole point of a DVR is to record stuff when you’re not there/asleep so turning it off (and the receiver that feeds it) somewhat defeats the purpose.

  12. The analysis from David MacKay’s Sustainable Energy without the hot air came to a conflicting conclusion: that the little “vampire” loads are so dwarfed by the big items like the oven & house heating/cooling that you won’t get any major reduction in overall power consumption from looking at the small stuff alone.

    Or, to borrow a phrase from the book: If we all do a little, we only accomplish a little.

    As boxspring mentioned, I find the proposal to use a (guesstimated) 200-watt computer (that would have to be on 24×7) to turn off 1-watt loads around the house very odd. Why not leave the microwave clock alone & turn off the computer to save more power?

    1. I immediately thought about that book (which, of course, was recommended on Boing Boing some time back). This post might be more convincing with some figures on how a house’s annual power consumption divides up.

  13. The idea of a zero-energy house, which is what the title and first paragraph of this article are about, is an interesting and cool one.

    Maternal nagging to turn the lights off when you leave the room, which fills the rest of this article, is less interesting and quite a bit less cool.

    The fact that said nagging fails to account for material efficiency causes the whole thing to descend into trite aphorism. Is it really worth going out and buying a circuit timer to regulate your microwave clock? Not to mention all the applications where it’s more efficient to leave things on. Applications like CFLs, which lose 20 minutes of their lifespan each time you turn them on and off. CFLs which are environmentally hazardous to produce and dispose of.

    Does environmentalism qua environmentalism annoy anyone else?

  14. I would like to see building codes that mandate solar power on the roofs and parking lots for developments that exceed a certain area. Large big box warehouses, office buildings, storage lockers… They should all be generating power (and perhaps storing rain water) rather than just sitting there..

  15. My brother and I are building a net-zero energy house and if I can swing the electrical engineering, it’ll have automation to deal with occupancy and plug loads.

    Check it out at

    Self promotional plug: we’re looking for sponsors.

  16. I agree that phantomloads are worth stopping, but until clocks auto-set themselves, it’s not worth it to me to reset it twice a day.

    “over the course of a year, all the electricity you used to run that microwave clock ends up being enough to power 30 hours of microwave cooking time, Peterson says.” – so, 2.4W, or 0.05KWh/day, about a penny a day, £3.65 a year.

    Nope. Phantom loads do not appear significant. This is another “recycle plastic bags” effort: it’s feel good but accomplishes little compared to the volume of plastic/electricity wastes elsewhere.

  17. Energy: I don’t think that word means what you think it means.

    A zero-energy building would be a very cold, empty place. The immediate boundaries of said building, on the other hand, would probably need to consume quite a bit of energy just to keep any stray energy from entering the zero-energy region.

  18. My vote is for some Aerogel insulation…

    That would be hot, err.. or cold, or at the least very insulative.

    You know I like all these ideas, but frankly I don’t see this actually happening in practice.

    Build a house with 6 inch exterior walls provides more insulation, insulated roof rafters (or a false roof), ect… But these all cost money. And unless you are building it, and paying for it yourself then I doubt a builder is going to pony up the extra cash in hopes of selling it.

    OH, and something on the Energy Star thing… I call BS. Alright, it’s perfectly reasonable to measure and compare the efficiency of something large like HVAC. But my fridge is a perfect example: if it is below 60F in the house the freezer is above 0F… I suppose it’s a design flaw, but it is very obvious that it was designed with a very narrow range of operating temperatures. (The reason the freezer thaws is there is no separate thermostat for the freezer compartment. The dial in the fridge area simply adjusts the amount of cold air entering the freezer when the fridge section runs. As the outside temp drops the fridge needs to run less as the delta T is much smaller than that for the freezer.)

  19. Zero Net Energy (ZNE) is a far cry from Carbon Neutral (CN) …and the latter is what we need to address real problems. If you build the most inefficient house ever (with the most inefficient appliances) you can still reach ZNE by slapping $400,000 worth of solar panels on the roof. It means almost nothing especially when you consider the energy spent to create new appliances, building materials and construction itself.

    Carbon Neutrality is achieved by creating enough supplemental energy through its service life to offset the carbon emitted as a result of its construction. There are only a few folks in the world seriously committed to addressing and eclipsing the idea of ZNE as a worthwhile goal and I had the pleasure of working with one of them in the US a while back. If you’re interested in learning more, they have a pretty stellar blog called the Nauhaus Idea Repository where they discuss issues like this. You can find it and other awesome educational info about their think-tank and prototyping work at

    Maybe that’s a shameless plug, but coming from an educational background focusing on sustainability and then getting to intern with an organization that broke all the greenwashing and half-assing down to what it was really helped me personally.

  20. Typical household energy consumption:

    32% space heating
    13% water heating
    12% lighting
    11% air conditioning
    8% refrigeration
    5% electronics
    5% wet-clean (mostly clothes dryer

    Residential uses 21% of the energy used in America, and space heating is the biggest chunk of that (other than in the South). It is possible to build hyper-insulated homes which can basically be heated by little more than the heat produced by electronics, refrigeration, and lighting, but it is rarely done.

    Regarding vampires: Vampires simply don’t use much power compared to the other biggies. So I think hyping on vampires is ridiculous. We need better-insulated homes and solar water heaters, not vampire control.

    1. Any ideas what the numbers are for the South? It seems like A/C should be a huge energy consumer, especially commercial.

  21. I agree with Dewi, one problem with switching many appliances off is that they have no memory. My DVR has to maintain a clock function in order to know when to turn on and record a program.

    This actually can save power, since while watching I’m using much more power, but by skipping commercials and playing programs 30% faster, I can watch a one hour show in about 35 minutes. So that’s 25 minutes my whole home theater doesn’t have to be on. About a 40% savings.

    I’m also curious about the Lawrence Berkeley Labs data DwellArch mentioned. The average set-top box DVR draws 29 watts when it’s recording, but almost 37 watts when it’s OFF? Somebody’s not doing it right.

    Euro-2013 requirements and coming requirements from California and other states are about twice as stringent as EnergyStar, and are not voluntary. Manufacturers will not be able to sell in those markets if the standards aren’t met.

    These also go far beyond standby power to include limits and efficiency requirements for operational mides as well. For example, the efficiency requirements for audio power amplifiers is strongly pushing the industry towards switch-mode amplifiers, audiophiles be warned!

  22. MA has been working on a zero net energy initiative for the last couple of years, since Deval Patrick became Governor, and is building at least one zero net energy state building. They finished a zero net energy house contest whose winner was announced in March at the Building Energy conference. Here is my report on it:

    Of course, Germany, Sweden, Denmark, the Netherlands, Norway… are ten to twenty years ahead of us on this. There’s a lot we can learn but there’s already a lot we can do on our own.

  23. Just to be clear is Kent Peterson talking about a 50% saving in existing stock, not new buildings? Does anyone have a link to the studies he is referring to? Or even the title?

  24. My entire entertainment center shuts off at the strip when I turn off the TV, you can buy a monster cable strip or a rocketfish strip that has a master outlet. When it senses the power shut off, it shuts off all the outlets and waits for the master appliance (my tv) to come back on. Also you can buy power strips with wireless rf wall switches that can connect up to 3 or 4 strips, hit the switch on the wall, they all go down.

  25. I think part of the confusion around vampire loads and their (lack of) importance is because the people who know the most about energy draw are often building off-grid systems. Without the grid to take up the slack you’re only generating as much power as you need, when you need.

    Grid-tie solar power systems are a more useful model for people who aren’t interested in unplugging: sell what you don’t consume, buy only when you need it.

    Zero-energy buildings is a dead end: what we really want is zero-energy neighborhoods. Except with a less creepy name.

    But as noted above, the companies who don’t want this to happen wield disproportionate political clout.

  26. How many people who do NOT read this site, and others like it could cope with the complexity of a zero energy house? All 4 of my parents, my grandparents, and most everyone in my family have a enormous problem dealing with any kind of technology. Remote switches? Putting in AND PROGRAMMING timers? No one I know has a TV that doesn’t need to be resetup when there is a power failure. My grandparents still have a 10year old analog broadcast TV. I still have to train the monkeys^b^b^b^b^b^b folks to run stuff.

    About 8 years ago I DID the automated, motion controlled lights and zones. Between the cost of the switches and the LARGE expense of finding DIMMABLE CFL’s (that are compatible with a X10 light switch) I figure I NEVER recouped the cost. In the end I stuck with manual switches and cheap CFL’s as the best cost/value mix. The glazed over looks on people’s eyes when I explained the system told me that it was simply beyond them.

    1. As for the “complexity of a zero energy house” I think the commentators who’ve pointed out that all the electrical management gimmicks are really in the noise probably have it right. For example see #28 and #31. What this implies is that if you prioritize sensibly and focus on stuff like having a superinsulated shell for your house, you will save both on construction costs (relatively cheap, boring old technology) and complexity (there is nothing to program or really, understand about insulation — it’s just there).

  27. I checked a few things. I wrote Kent Peterson and the study he cited is for commercial buildings, not residential.

    Have not had time to look at the actual study yet only to skim the exec summary, but in terms of efficiency, apparently we could save overall 43% of the energy per square foot in existing commercial building stock, presumably a great deal more in new buildings, and then add PV to the rooftops to provide most of the rest. Two gigantic ifs on the PV. One is the assumption that the grid could handle this. One hell of a lot of storage, demand management and backup would have to be in place. The other is that PV would have to come down a great deal in price. Neither of those is impossible, but neither is in place at the moment.

  28. But wait, the amount of calories I’d have to consume to give *me* the energy to turn off lights, pull out unused power cords, say nothing of shopping for cfl’s and energy star appliances…

    Hell even thinking about this is draining a few calories. How to offset?

  29. Here we go again. What’s the pay back time for all the kit needed to be able to disconnect from the the grid? Home wind power is 7 to 10 years. Is the kit usable in the majority of properties? Home wind power dose not work in built up areas, guess where most of the people live. Can you fit a small wind turbine to a flat (condominium?) outside wall?

    You will still need a grid connection as the availability (read reliability) is nowhere near as good as the grid and guess what, we are all going to moan about the increasing cost of having to keep a grid connection as fewer of us will use it to keep the costs down.

    There are reasons that the utilities were centralised and they are just as valid today as they were 50 years ago.

    1. 7-10 year payback seems like a dead obvious win, the more so since it ought to add to the value of the property commensurately.

      As for reasons for centralization being just as valid as 50 years ago, I see no particular reason to believe that. Given your spelling one might guess you don’t live in the U.S.. At least here, there are vast tracts of single-family houses and low-rise business development that would seem to be tailor-made for PV installations. Yeah, a grid makes it all easier since you don’t need local storage, but if you can get rid of most or all of the peak plants, you’ve won a lot already, and move forward from there. Oh, and storage technologies aren’t standing still either.

  30. Except that he has to leave a computer on 24×7 to turn other things off… I hope it’s a low-power one.

Comments are closed.