Your biggest solar-charged miles thief: Central AC

Our central AC unit.

After seven consecutive days with highs in the 90s, including a 101-degree scorcher two days ago, editors-blog-entry3we turned on our central air conditioner for the first time of the summer 2010 last night — and for the first time since we had a 5.59 kW solar system installed on our Aurora, Colo. roof.


Here’s hoping it’s the last time we turn it on this summer.

I knew central air conditioners hog energy. Still, it was shocking to see just how insatiably our central AC unit gulps down electricity.

Thanks to our new digital utility meter, which makes it far easier to figure out exactly how much electricity you’re using than the old spinning dial meters, I was able to determine that our AC unit sucked down about seven kWh of electricity in about an hour and 15 minutes. That’s nearly twice the total of the four kWh we’d been using per night up to that point with our one ceiling fan plus one large window fan and lots of open windows combination.

Central AC robs Sun Miles™
Watching our AC unit rob the Sun Miles™ — Solar-powered miles driven by an electric vehicle (EV) or plug-in hybrid electric vehicle (PHEV) whose batteries have been charged using solar energy — we’ve banked for a future EV at a voracious rate made me think about a few things:

  1. First, I’m glad we can get away with not running the central AC in our house much (we did not turn it on once last summer!). We get away with this for a few reasons. Our south-facing, front-side of the house has only one window – and the sun shines into that window only in the winter, not in the summer. This keeps the house cooler than many other homes in what can be a baking Front Range of Colorado in the summer.
  2. Second, we’re willing to “suck it up” and wait until temperatures push 84 degrees upstairs and there’s no wind to help cool things down before we’ll turn on the AC. Some might think we’re “crazy”. But what’s crazier to me is what comfort hogs so many of us have become — to the point where we claim to be “suffering” if the temperature in our home rises above 76 degrees. Horrors!
  3. Third, not everyone is as fortunate as we are to: a) live in solar-friendly and sunny Colorado; b) live in a dry climate where heat is more tolerable than in places like Florida, Louisiana, etc.
  4. Fourth, not everyone is willing to “suck it up” like us and “tough” out the heat (we’re really not that tough) with window and ceiling fans only + well-timed trips to our perfectly comfortable furnished basement.
  5. Due to 1, 2, 3 and 4, many people won’t be able to – or, in the case of No. 4, most likely do not have the will to — bank the Sun Miles™ at the rate we have been so far. We’ve generated almost 2,000 of these future EV miles after only three weeks  with a home solar system based on the nearly 500 kWh of electricity we’ve generated beyond what we’ve used in those 21 days.

That said, I know there are plenty of people who could bank future EV miles with a new home solar system just as quickly as we have, perhaps even more quickly.

At what temperature is AC ‘necessary’
Ok, some of these people live in the ultimate temperate + great solar climate of Southern California (I’m talking about places like Santa Barbara, San Diego, etc. here, not Bakersfield, etc.) and don’t need AC — plus they barely need heat in the winter!

However, many people who could bank Sun Miles as quickly as we are right now live in a more marginal climate (like Colorado’s Front Range), where they could easily get by with rarely using their central AC — if they’re willing to endure a tiny bit of temporary and comparatively occasional discomfort .

I’m skeptical many people will do this. But I could be wrong. After all, the potential gasoline savings to be had is significant – and sweating just a bit more in the summer will also get many solar-charged drivers damn close to completely air pollution free driving. That’s pretty good incentive, and it might just be enough to inspire some people to turn down their AC now so that they can turn up the EV later!

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