Posted by: jdantos | September 23, 2012

Solar Panels

Solar panels, on our roof.

This spring, we put up 11 solar panels on the roof of our little rowhouse, both a small step towards more sustainable living, and a hopefully financially sound investment.  After joining the waitlist for a grant from DDOE’s Renewable Energy Incentive Program program a couple years ago, we had done a shading and usage analysis, and collected bids and chosen a contractor, but then kind of forgot about it for 2 years.  Then, this spring, our number finally came up, and before we knew it our contractor arrived, ladders and electrician in tow.

How Much Power? The size of the system was basically determined by 1) the size and configuration of our roof, and 2) how much electricity we consume. We settled on 11 panels, each of which can produce 220 watts or so.  Unless you remember what a watt is from 3rd grade science class (I didn’t), that means that when the sun is shining bright, directly overhead – the system produces 11x 200 = 2.4 kilowatts.  If that happens for one hour, that’s 2.4 kilowatt-hours (KWH). And KWH is consumption – it’s what your electricity meter keeps track of, and determines your bill. In fact, your bill probably says how many KWH you consumed last month.  Of course, the sun doesn’t hit a panel straight-on all the time, so you don’t get aximum output from sunrise to sunset. We figure we use 10 KWH per day, on average, so after much math we figured 11 panels would probably cover most, if not all, of our average annual consumption.

Installation in progress

How Does It Work? The installation is pretty simple, really. The panels are mounted on a basic aluminum frame a few feet above the roof’s surface, connected together, and then one wire runs down the front of the house right by a gutter and connects the panels down to our “smart” meter. Each panel has an individual micro-inverter, meaning that the system isn’t like Christmas lights of old – if one panel goes down (or is shaded), the others keep producing. The support structure never punctures through the roof. There are no batteries– our power is distributed right out onto the grid in real-time through net-metering. When we produce more than we use, the meter “spins backwards,” and vice versa. Our smart meter takes the net difference between what we produce and what we use.

Return on Investment. The system wasn’t cheap to start, but a DC grant, federal tax credit, and these cool wonky things called SRECs made it a worthwhile investment in dollars and cents terms alone, even aside from the “green” part. I won’t delve into too many details here, but basically it was a tradeoff between upfront costs and reducing our electricity bills to zero.  Return-on-investment will depend on a few things, but we expect about a 5-year payback period. The panels have a useful life of 20 years until their efficiency begins to fade.

Subsidies? Yep, we were subsidized to take on this project. Without the subsidies, the payback period would have been longer than we were comfortable with. But, I think the subsidies are having other positive effects – helping contractors gain experience and lower their costs, and helping spread knowledge of solar to residents and would-be customers. And, as a grant recipient, DDOE has required us to participate in “green homes tours” and the like. I’ve had many sidewalk conversations with my neighbors explaining it!

Monitoring data

So Far So Good?  We had a few hiccups that cut into production in July, but other than that, it’s been working out well.  We became an “official” power plant in June, and our bills from Pepco have been about $7 a month (turns out there’s some fixed fee every month). The panels didn’t fly loose during the derecho, either (whew). The July problem had to do with Pepco’s line on our block, and it was resolved it pretty handily. Essentially, we just watch it – no maintenance required.

Typically, we’ve produced more power than we use during the day, and then we consume it back again in the evenings when the lights, TV, and appliances come on. Sometimes I glance at the meter on my way out the door in the morning, and then again in the evening, and I can see it’s moved backwards by maybe 10 KWH. Then, the next morning – after a little TV, laundry, and a window fan the night before, it’s back up again, closer to yesterday’s number.  Production at the equinox now is down about a third from the long days around the Solstice.

We’re still just about breaking even – not sure if we’ll still be in the black after this winter when the days are short. But, I doubt Pepco will ever send us a check!

View from the sidewalk

Has Much Changed? Beyond the dollars and cents, the project has had a few mental impacts too:

  • The panels are visible from the street, and they definitely don’t look historic! Sometimes I think they look ugly; other times elegant and sustainable. Maybe now I don’t even notice it.  What do you think?
  • The monitoring system and software tells me every minute detail about our electricity, so I pay a lot more attention more now.  I now know production by panel, by 5-minute increments, and can share it with you, and there’s even an app for it. So, this has made us much more aware of how much power we use and produce. Now, maybe I’ll remember to switch off that light, or decide to hang a pile of laundry rather than stick it in the dryer. It can be a mini-contest to see if the next Pepco bill will actually be negative!
  • I pay more attention to the sun these days. A bright sunny day now means a lower electricity bill.
  • Guilt-free air conditioning in the summer.  ‘Nuff said.

If you’re interested in learning more about doing something similar to your house, I’d start first with DDOE’s materials on the program, and a great resident-led organization called DC SUN (Solar United Neighborhoods). I’ve heard word that DC’s next step might be solar hot water heating, not just photovoltaics. The absolute first step is to get your name on the waiting list.

Or, email me offline for more specifics. Heck, I’ll even give you a rooftop tour.



  1. great post. besides addressing the market failure, the subsidies help create a ‘track record’ for the market value of having solar panels. having a bunch of data points saying “solar panels add $XxXX to the value of your home” will help people make the investment on the open market. I’m waiting to see local data on that before i take the plunge, b/c wife and aren’t planning to be in our house for the payback horizon

  2. A fine summary of what it’s been like for us as well; we had a largely parallel experience with our Capitol Hill townhouse (year-plus delay before DC offered a grant, quick installation, June activation, and frequent tracking of our system’s performance via the web).

    We put a bigger system (6.4 MW) on a bigger house, and even so it doesn’t fully offset our summer (A/C-heavy) load. In September we turned the A/C off, though, and the sun is turning the meter backwards. As you suggest, we expect to to owe Pepco something as days get shorter and we spend more time indoors, but spring should put us in positive territory again.

    Just as you describe, the system is maintenance free, sound free, and entirely (for us) trouble-free. We should recoup our costs in 5 years or so, after which the cost savings is pure gravy on top of the satisfaction of knowing the sun meets most of our annual energy needs and we’re not straining Mother Nature’s limits as badly as we used to…

  3. We put 18 panels on our roof in 2008 with a grant from the city. We still had room for a nice deck. My out-of-pocket cost was about 12 K. Our house is totally electric except for my cooktop which is gas (my preference). We have guests for cocktails and dinner on my roof and I am proud to tell them to watch the sun put money in my pocket. RECS included, our yearly energy cost is net zero, which includes heat, AC, and lights. I had gutted and renovated at the same time and was careful to insulate properly and use energy-efficient materials and appliances. The project was a great success.

  4. I also went solar when we renovated our current home in Hillcrest and have been very happy with the results. Not only are the bills lower, we are getting SREC checks 4 times a year and that is the only part of the renovation that is paying us back!
    You need to get moving if you want to take advantage of the DC program and the federal tax break. Please go solar!

  5. Fascinating stuff. Thanks for the report!

  6. Guilt free air conditioning is right… I definitely don’t think they are aesthetically efficient, but who cares about what they look like when you get money back from the electric company?? Hahahaha.

    -Sharone Tal

  7. I read your project I really like it.
    I have a row house similar to yours. and i was asking my self what is your are where u place the panels?
    Have a great day

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