Things I learned in my “net-zero” energy home

Have you ever noticed that you hear a lot about “net-zero energy” homes or buildings that have just being designed or are just being built?  You almost never hear anyone announce that they got their first year of utility bills and actually were net-zero energy.  When construction was completed on our house last year, we vowed to be the exception.

So, I am happy to announce that between 8/23/11 and 8/31/12, we purchased 5843 kWh from Progress Energy, and we sold 6147 kWh back to them.*  The 304 kWh difference puts us in positive territory – by about the amount of a mini-fridge.

I wasn’t surprised to reach our goal, but I was surprised by some of the things we did to get there.  Probably because I’m in the “green building” industry, I spend a lot of time focusing on how to design and build efficient homes.  So, I suppose I can be excused for not initially focusing enough on the “operation” aspect of net-zero.  I’m not the first person to make this mistake.  Professionals design homes and other buildings.  Regular people operate them – busy people who don’t think about energy efficiency 24/7 and who just want to plug stuff in.

Our solar PV array went “live” on August 23, and I decided to happily live my life for a couple of months before checking in to see how I was doing.  Mid-November, we installed an Emonitor to record our energy use by circuit.  Suddenly I had endless data to analyze.  Heating and cooling energy use is easier to understand when you have a whole year, but I could tell that we were somewhere in the ballpark.  We were also using less hot water than my modeling predicted.

But then there were those pesky “lights and appliances”.  Some of it just can’t be avoided – the systems that make our house efficient (the ERV, the cistern pump, the solar hot water pump) are using about 600 kWh per year.  Obviously, I see our refrigerator, dishwasher, computers, and even the Tivo as essentials.  I figured that we needed to keep all this “stuff” under about 4600 kWh if we wanted to actually be net-zero.  At our current rate in December 2011, we were projected to use about 5300 kWh.

I went on offense and action was taken:

  • I found a whopping 1404 kWh in potential savings getting rid of parasitic loads and using better power management practices (ie, turning stuff off religiously) in our home office.  Everyone was on board immediately once we all understood how wasteful it was.
  • I found a potential 412 kWh per year savings with the TV/speakers/ancient cable box in our master bedroom, but we discovered that if we switched the cable box off it forgot all its settings and had to go through a half-hour startup every time we turned it on.  We ended up replacing some equipment (including the cable box) with new versions that had much smaller “vampire” loads, and achieved about ¾ of this savings.
  • I estimated that we could save about 230 kWh per year if I used a clothesline half the time to dry our clothes.  (Note:  our savings is probably smaller than it would be for most people because we don’t do that much laundry and we have an Energy Star clothes washer, which saves on drying).  After whining and procrastinating until May, I was finally shamed into it by students in my class at AB tech (thanks guys!).  It’s not that hard, and I’ve been hanging stuff out all summer. 

I went on defense too, and action was not taken:

  • We decided against a water feature in our yard because the pumps are big energy user.  Also, it sounded expensive and like it would require a lot of maintenance.
  • We decided against an active wine cellar or kegerator or any form of active adult beverage refrigeration.

Yes, I’m aware that these are first world problems.

We implemented our savings partway into the year and still made our goal, so I’m pretty confident that we can meet it next year  even if we have an actual winter.  Since so many of the things we did are things that we should have been doing 20 years ago, I’ve become newly committed to the idea of “hypermiling your house” and spreading the word about how easy that is to do.

* By the way, don’t try to do any math with those numbers – we’re net metered, which means we actually used and produced more energy than these data suggest.  Power usage that’s concurrent with production is “cancelled out” and doesn’t show up on our bills.

Copyright 2012 Amy Musser