Home solar means near net zero energy use

editors-blog-entry3Thanks to the fact that we bought our 5.59 kW solar system before we bought an electric car, which, in fact, we still haven’t been able to buy, we’ve produced 10,000 more kWh of solar electricity than we’ve used during the 27 months our 26 REC panels have been up on our Aurora, Colo. rooftop.

Of course, the fact that we’ve overproduced so much solar electricity – enough to run another entire average American house for a full year – isn’t solely attributable to the fact that we don’t have an electric car.

We’re also very energy conscious. Our household of four – last year, for seven months we were a household of five when we hosted a German exchange student – uses less than 5,000 kWh per year. In fact, in May of 2011 we even managed to use fewer than 200 kWh in one month.

Given that we’re producing so much more electricity than we’re using – 200 percent more electricity to be exact! — I’ve started to wonder whether we might have a net zero house gig going here.

The “net zero thing”
On a basic level, a net zero home is one that produces as much energy, on site, as it uses across the period of a full year, though, as you’ll see in the video clip above, the whole “net-zero thing” is actually more nuanced, complicated, and, frankly, even potentially confusing than that.

I know our house – which is a 1978 box with a true “welcome-to-my-garage” look (luckily, the giant garage roof faces directly south 😉 – doesn’t qualify as a traditional net zero home on a completely “pure” basis. For example, it certainly wasn’t built via energy-conserving construction methods. But it seems to me that if we don’t qualify as a “pure” net zero home, we’re coming close to being net zero.

Our main stumbling blocks right now are our gas furnace and gas hot water heater. But, as you can see by the screen shot at the end of this story of our utility bills over the past two years, most of our monthly utility bills for electricity and gas are $25 total (with more than one-third of this taxes and fees!). That means we’re not burning very much natural gas.

We’re going to be burning even less natural gas this winter. That’s because I will be using six eheat.com efficient electric wall heaters – they’re 400 to 475 watts each — to cover as close to 100 percent of our home heating as possible. This will help us eat up some of those 10,000 extra solar kWh – I’m guessing about 2,500 kWh or so, though, of course, we’ll easily add these back again between April and August of 2013.

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Natural gas water heater a problem
That still leaves our natural gas water heater. However I’m guessing that if I was ambitious enough (I’m not) to go through all of our utility bills for the past two years and add up the therms worth of natural gas we’ve burned and also “guestimate” how many of those therms went to our hot water heater as opposed to our forced hot air furnace, we might be net zero over the past two years, or, at the very least, very close.

After this winter, which will hopefully see our furnace burn very few, possibly even zero, therms worth of natural gas thanks to our unique “solar PV-powered” home heating set-up, it should be easier to figure out how many therms our hot water heater has used, do a therms to kWh conversion, and establish with a bit more accuracy whether we are a “true” net zero house or not.

If we’re not already a net zero home, there’s no doubt we’re damn close, certainly a hell of a lot closer than 99.9% of American households, and, as I note in the video clip above, we’re all very proud of that 🙂


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