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Solar Panels on our Roof

Page history last edited by pinkhamc@... 10 years, 6 months ago

This summer and fall (2012) we investigated the pros and cons of putting solar panels on our roof.  This is the story of our decision.  Perhaps it will be helpful to others considering the same move.


The idea of putting this site up came when I responded to a post by Bruce Lisman of CampaignforVermont. If you are not familiar with his site, I highly recommend it.


Here is my response, which was also sent to Washington Electric Coop and SunCommon:


"My wife and I are on Washington Electric, which we applaud for their ability to keep the electricity flowing under the direst of weather conditions and their eagerness to harness renewable resources.  We recognize their residential rate structure is different from most utilities in the state with the first 200 kWh costing 9 cents/kWh and all above that costing a much more expensive 21 cents/kWh.


However, we also recognized that price structure as a boon to our retirement pocketbooks.  Recently we negotiated with SunCommon to place a solar array on our roof.  We know the cost of PV panels is going down as the technology improves, but we had to jump in sooner or later.  Time will tell if our timing was providential.  However, one part of our decision is clearly useful even now.  SunCommon offered to build a system that would completely cover our current consumption.  However, the cost for this was about $20 more than our current electricity bill.  When I objected, they provided plan B: a system that would cover all but about 200 kWh per month.  This system plus the cost for our usage of WEC energy will cost approximately the same as our current power bill.


But therein lies the wisdom of our solution.  Under the former, there would be no incentive to decrease our consumption of electricity since we would get no refund for extra energy pumped into the WEC grid.  Under the latter, the more we can cut down on our usage by converting to LED lights, by purchasing more energy star appliances, and changing our behaviors, the less the system will cost until we completely eliminate the 200 kWh base.


Can this approach provide a solution for others in WEC?  I am certain it can.  Will it help Vermont solve its energy problems?  I am not clever enough to know."



So far I have received encouraging responses from both Washington Electric and SunCommon.  They follow. 


From Washington Electric:



Thanks for sharing this with your Co-op.

I’ll be working your logic into our conversations with other members who haven’t yet put the time or thought into the same decision you have made.


Bill Powell


William Powell, C.E.M.

Director, Products & Services

Washington Electric Co-op Inc.


From SunCommon:


Thanks Carl,

We are excited to be in this together, solving our energy and environmental problems while saving Vermonters $. 

Thanks again and stay in touch.

Cheers, James


James Moore


We have also learned that our response has produced a lot of discussion at CampaignforVermont.


As the project proceeds, we will provide pictures and data as well.


Solar Panel Plans and Progress:


Views of roof with 12-month solar prediction using the SunEye (not our house, but you'll get the idea).


The SunEye held over a roof in position to take readings:


The SunEye instrument that is mounted on the top of the pole above:


Closeup of the SunEye display.  The edge represents the horizon.  The black lines represent where the sun will be at different times of the day and the blue lines at different months of the year from June-December.  A similar reading is taken for January-May.  Where trees obscure the readings, the sunlight will be diminished.  Our roof was practically tree free.


A resource for calculating expected exposure at your location: http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/


The predictions made by this resource and actual results from our system are here:

Predictions and Records for SPs.xlsx


Project is getting underway (12 11 16)


The plan for the solar panels:



The roof before installation

Equipment trailer

Construction sign

Solar panels in shipping container

Unpacked solar panel

mounting tracks on the roof


mounting tracks from the ground

Mounting hardware and the J-box

Panel connector and DC run

Installation underway

DC line from roof

Inverter in the basement

Utility disconnect (left), production meter (center), utility meter

Our friendly and successful installation crew: Htway, Curt, Brian

Solar panels cooking



This is the link to our system.  Unfortunately you need an ID and password, so it's here for our use only. Solar Panel Production History  weather on Nov 20th: partly cloudy; 21st: high thin clouds; 22nd: mostly clear skies; 23rd: off and on cloudy; 24th overcast and snow starts at around 11 AM; 25th-27th essentially overcast skies with the 27th being the heaviest; 28th overcast.


here is the latest entry screen when we log into our site.  As you can see, on the best day we generated 11.75 kWh.  Today, the 17th of Dec, we are generating zero because the panels are covered with three inches of snow, it is heavily overcast and still snowing, and it is supposed to warm up and all the snow will be melted off the panels anyway.  If I were to remove the snow that's there, I would only get about 1 kWh (I did that yesterday under the same weather conditions), so I don't believe it's worth the effort to remove the snow again today:



Then our wonderful Vermont winter hit.  I was convinced I had to keep the snow off the panels (the first big snowstorm piled 2 feet on them) and I spent a good part of a day carefully propping my ladder against the roof so I could use a snow brume and a 15' telescoping handle to remove the snow.  It snowed the next day and although I got some power out of the system, it wasn't much, so after one more stubborn try with the same outcome, and Chris's telling me I was crazy, I finally gave up trying to best mother nature.  That's when we got the following blog from SunCommon.  http://suncommon.com/featured-solar-faq-what-should-i-do-about-snow-on-my-solar-panels/.  It's worth checking out if you are considering solar panels for your place.  It turns out, once more, Chris is right.


On the 9th of March, 2013,  2/3rd’s of the solar panel array was covered with about 14” of snow, the other third was covered with about 6”.  We have always had snow drifts on the roof half on the leeward side of the peak where our panels are mounted.  We live on a slope with a long reach from the valley.


So on the morning of the 10th, because of the weather forecasts, I uncovered  the bottom 6” of the lower row of panels.  Over the day that area expanded and a strip at the top became exposed.  Over last night the melting continued.  This morning the panels were 2/3rds exposed and now they are starting to generate electricity.  Yeah!


I need to update the above info, but more importantly, I need to draw the reader's attention to the following article:

"Tensions rise as credits for solar cut into utility budgets; VEC is the third utility to hit 4 percent cap" which addresses something I didn't know about

"net metering clients — those customers generating electricity from renewable sources at less than 500 kilowatts per hour (kWh)."


The quote below was excerpted from an article published in VermontBiz.com at the following link: http://vermontbiz.com/news/august/alternative-energy-advocates-upset-wecs-limit-net-metering?utm_source=VBM+Mailing+List&utm_campaign=24439f7669-E_Enews_8_15_20138_15_2013&utm_medium=email&utm_term=0_85838110bc-24439f7669-286276378

entitled, "Alternative energy advocates upset with WEC's limit on net metering"


"Net metering is defined by Vermont law as the difference between the electricity supplied to a customer and the electricity that a customer’s renewable energy system feeds back to the grid.


"In 2011, the state’s net metering program was expanded. The way net metering in Vermont works is that for each kilowatt-hour (kWh) a customer produces, the utility must provide the customer with a 20-cent credit, minus the utility’s highest residential rate per kWh. For example, if a utility’s power rate is 14 cents per kWh, then the net credit to the customer would be 6 cents. The law also increased the maximum capacity of net metering projects to 500 kilowatts. [With WEC, the maximum power rate is 23.5 cents per kWh, so it looks like we would have to pay WEC 3.5 cents per kWh that we produced above what we used, and thus, was fed into the grid.  This does not feel right, so I wonder what I am missing.]


Under the law, utilities are required to take on net metering customers until the total capacity of those systems equals 4 percent of the utility’s peak demand during 1996 or the previous calendar year. Due to the intermittent nature of renewable energy, such as with solar and wind-based systems, the actual energy output of a given system is a fraction of its capacity.


Washington Electric surpassed the 4 percent cap at the end of 2012, with 138 net metering installations [and we were one of those 138], totaling 683.4 kW. Four percent of the utility’s 2011 peak was 635 kW."


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