SURVEYOR'S NOTEBOOK

Solar Math Update

By Rik van Hemmen

I installed roof top solar on my house in July 2017 and wrote a blog about it promising to provide an update in a few months. I did not get to it until now, but after more than two years of operation it is even more fun to revisit the project to see how it turned out.

Overall it has been a delight, and it continues to be a seamless set-up that I would recommend to anybody who has the roof and sun to pull it off, but there have been some unsuspected, almost hilarious, side effects.

When the system was first up and running I almost obsessively checked power production on my smart phone app, and occasionally noticed high spikes in real time consumption. That made me call home and ask Anne what was going on. It took a bit of discussion, but the answer was obvious; the spikes were caused by Anne’s use of our electric clothes drier. This resulted in a debate as to whether Anne should dry the clothes in the yard. Anne, being smarter than me, said she would hang the clothes outside to dry if I rigged the clothes lines first. Somehow, she must have know that my obsession would pass and I never rigged clothes line in the backyard.

The first fall and winter was unusually cloudy and I did not see the production I had hoped to see. The summer of 2018 was weirdly hot (lots of AC) and cloudy, but when I was ready to evaluate a year’s production (September 2017 to September 2018) I threw a wrench into my own analysis, since in early September 2018 I chose a Chrysler Pacifica Plug-in Hybrid as my new car, and this car is charged at my home, thereby increasing my home electric consumption.

In teasing through the analysis I think I was a little short in producing all my electricity and came in at about 90% for a full year’s run September 2017 to September 2018.

Overall, Anne rarely saw a positive electric bill through the year, but once the car was charging at home, Anne would jokingly complain about my car increasing her electric bills. Now the car adds about $35 to the monthly bill and I drive it on electric for about 9000 miles per year. This means I get 21 miles per dollar from the car on electric. With gas at $2.50 per gallon and at 30 mpg in hybrid gas mode (yes, that is what I get in hybrid gas mode on the minivan), I get only 12 miles per dollar. By itself, an interesting operating cost comparison for plug in cars.

Plug in Pacifica and solar panels on roof at far right. 

As a compulsive treehugger, I changed my electricity provider to an all-wind supplier (standard NJ electricity still has a large coal and gas component), so, strictly speaking, what I do not produce in solar, I consume in wind energy. Therefore, for about half of my total miles, my car is actually powered by wind and sun. (Interestingly, I pay less for the all-wind energy through Liberty Power than I would pay for electric supply from JCP&L. It all comes down to timing and searching the web. JCP&L are not the bad guys, their bill actually shows what rate you need to beat the JCP&L rate.)

I am now short in energy production capacity on my roof, and am thinking of adding additional solar panels to my roof and will discuss this with my solar system provider, hopefully soon. I no longer have ideal roof space, but since the support system is in place now, maybe adding the panels will be cost effective.

In reviewing my earlier blog cost details, I note that I ended up being a little short on production, so my bills did not get to zero. In other words, I ended up paying about $15 per month in electricity instead of $0. However, the SREC (Solar Renewable Energy Credits) have been coming in right on the nose and provide my $150 per month kickback. As a solar farmer I can take satisfaction in the fact that solar production in 2019 has been better than 2018. The graph shows that in mid November 2019 I have produced as much as all of 2018. Based on that, I think my full year 2019 production will be about 5% higher, which will take care of my 2018 “losses”. This is fun math; in 2019 I will buy less power from the utility and get more SREC money from increased production; a two way win.

Bottom line, this roof top solar stuff is as good as advertised, and the more of it, the better you will love it.

In late September 2019, we had one more interesting sustainability twist. Anne always cut the lawn with a gas powered motor. It did not consume a lot of fuel each summer (about 3 or 4 gallons) but did so very inefficiently, loudly, and with a high maintenance load (especially on me when it would not start). When Anne, once again, told me the mower would not start, I went on the internet to see what could be done and, fortunately, was confronted with the battery powered mower revolution.

We purchased a battery powered mower which does the 45 minute job without the need to recharge, does it much more quietly, with a much lower pushing effort, and requires no maintenance, no pull starting, no gas tank hauling or storage, and no oil changes. All for under $350! There is not a better deal out there folks, and when you charge it with roof top solar it is even better.  Super win-win, although soon it may also be the inevitable death of my cherished gas powered Stihl chainsaw. A battery powered one would be perfect for my needs. It is the march of progress, but if the trend is positive, there is no need to be sentimental about it. Death to gas powered leaf blowers too!

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