Wednesday, June 16, 2010

Solar Panel Update

Several people have asked for an update on the solar panels we installed. The panels were installed and became active in January (although our monitoring system didn't get activated until a week or so later, January 27th, so that's when all my easily accessible data will be from).

Overall, the system is performing well, even slightly better than expected. Here's a typical (sunny) mid-winter day:

And a typical (sunny) spring day:

A typical (sunny) day this week when it wasn't quite warm enough that we had the air conditioning on:

As you can see, we generated 20 kWh's more than we consumed.

And here's a typical (sunny) day when it was warmer, and we had the air conditioner on.

We didn't quite break even this day, but still not too bad.

Here's what the last month looks like:

And here's our total consumption versus generation since our monitor was installed on January 27th.

As you can see, we've generated more than we've consumed. For the past three months we haven't paid for any kWh's on our bill (although there is still a monthly fee to be connected to the grid). We'll probably continue to generate more than we consume through about September, maybe even October, then start dipping into that accumulated "bank" through the winter.

It's still too early to predict, but my guess is that we might finish our year with some still left in the bank. If that happens, they'll send us a check for the kWh's still in the bank, and then we start over again for the next year. (You can rollover your excess hours, which is better because when they send you a check it's at the wholesale price. But right now once you choose to rollover you can't ever change back, which means you'd never get "paid" for those excess hours that would keep accumulating if you generate more than you consume. We're waiting to see what a year or two looks like before deciding whether we want to switch to rollover.)

Overall, we're very pleased and would recommend anyone who's interested take a serious look at installing the panels (particularly if you live in Colorado, which is not only sunny, but has some decent incentives from our energy companies in addition to the federal ones).


  1. Karl, how large is the system in terms of kW? It looks something on the order of 6-8 or so.

  2. @Matt Montagne - Rated at 5.04 kW.

  3. Clearly there's a math lesson in here somewhere.

  4. @Jason Buell - Clearly, but I haven't figured a good one out yet. When I posted some charts a while back on Twitter I suggested that someone ought to be able to come up with a WCYDWT, but so far I can only come up with regular 'ole boring problems.

  5. Karl, Although I am not that familiar with the solar panel. I do know it is suppose to help out with the ozone, and I believe that is a great thing. I am glad it is working out for you so far and hope it continues.

    I think you can definitely make a math lesson out of it. Somewhere around the first week or two of school explain to your students what is going on with the solar panels, show them the graphs, and ask them to make a prediction about how much you will save in three months.

    This is only a suggestion, but I believe they will be interested in finding out how close they were in their predictions. It is also something they can relate to with you. Good luck in what you decide to do with your lesson and with the solar panels.

  6. Hi Karl,

    We e-mailed back and forth a bit while I was participating in PLP last spring.

    My husband and I have been renovating a home and recently had our panels installed. He drives a Prius (or as I like to call it, The Golden Pius), and while I drive a much less earth friendly vehicle, I've recently changed to a closer (2 miles vs 13) school in part to reduce my footprint.

    You're consuming less than you generate. What's your home's square footage?