When I replaced my aging torchdown roof with a new “cool” roof (white PVC membrane to reflect heat), I did so hoping to keep the house more comfortable in summer heat, and avoid having to install air conditioning, a known energy hog. But honestly I’ve had no real way of measuring the success of the investment, other than simply confirming that in the summers since, I haven’t needed AC.

But with my solar panels, I can get hard data, and lots of it, from multiple sources.

Enphase Energy, which provided the microinverters for my array, has a website that allows me real-time and historical performance data in monthly, daily, and even hourly views. If any of my 20 microinverters is malfunctioning, the site lets me know and specifies which one so the installer can fix the problem more efficiently.

Screen shot of Enphase monitoring website

The Enphase web-based tool shows how much power my array is producing every day. The better the production the lighter the box color. This shows that my best day so far came early on, with 14.1 kWh on October 19.

And if I forget to check the site for this information, Enphase bails me out by sending me a monthly summary email anyway.

As for Puget Sound Energy, the utility not only installed new digital meters when my panels went up, but they also familiarized me with how to read the pertinent information from the meters, and have included solar performance data on my monthly bills.

This level of feedback about my solar investment instills confidence that solar installers, the solar industry, and utilities are treating renewable energy as a viable, measureable option for consumers to consider on its merits. The numbers don’t always make me happy (I’m looking at you, November 28). But I’m grateful that this is one home improvement I can always assess accurately.

Just a quick entry today, with performance data from the first four weeks of my rooftop solar array. The news is both disappointing and hopeful.

During this time span, we used an average of 12.3 kWh per day, which is more than normal for this household. More on that in a moment. To meet that daily demand, just a tick more than half (6.2 kWh) came from solar power production. 6.1 kWh had to be purchased from the utility.

Over time, I think we’ll see the percentage of my electricity needs offset by solar go way up, from roughly 50% to closer to 100% or more. Here’s what I think happened:

  • Household demand was up due to wrapping up a remodeling project from the summer. Lots of power tools plugged in in the garage, and at one point a high-powered fan blowing 24/7. (Don’t ask…it had to be done.)
  • Solar production was weak for days at a time, as we got soaked with much higher than normal rainfall in October. What I’ve observed so far is that the array is of course highly productive on sunny days, surprisingly productive with the indirect light of partly-cloudy days, but scarcely productive at all on those wall-to-wall rainy days that the Pacific Northwest can sometimes have.

As we head in to the darkest weeks of the year now, it’s possible the array will offset even less of my overall electricity needs. But I knew this going in. Spring and summer of 2015 will be the big test.