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Solar Panels on Herndon Friends Meeting

In the spring of 2020, we decided to put solar panels on our roof to generate enough power to completely offset our use. Since it is a small building that is unoccupied six days a week, our requirements are small, so we did not need many panels. The roof itself was about due for replacement, so we opted for a metal roof first. But when you calculate the savings, it makes sense to go for solar now, regardless of when your roof is due for replacement. As a not-for-profit organization, the tax credit did not apply to us. We expect the panels will pay for themselves in electricity savings in around 21 years.

Meanwhile, we are happy that we can reduce our carbon footprint and demonstrate to our neighbors the feasibility of solar.

Here is what we learned from our research:

Even with Virginia’s restrictive laws on solar (which hopefully will be changed soon), it makes sense to invest in solar arrays for your roof now.

  • Good long term investment - solar arrays will pay for themselves within 10-20 years or so (and often less), even without a tax credit. The arrays will then continue to provide you with free electricity. If you sell your house first, the value of your house will be higher. (According to research by Zillow, homes with solar sell for an average of 4.1% more compared to homes without, which makes this a super investment even without the savings on electricity bills.)

  • Tax credit - Individuals and for-profit companies get a 26% federal tax credit in 2020, 22% in 2021, then zero for residential (10% for commercial properties) (unless the laws are changed).

  • Climate change - Our window of opportunity for avoiding worst-case scenarios from global warming is rapidly closing. The time to act is now.

Solar makes sense if:

  • You have enough unshaded roof space facing south (preferably), or west or east. Try looking up your address on Google's Project Sunroof.

  • You can afford the upfront costs, or you have an investor or get a loan. (see below).

Benefits of solar roof arrays for an average-sized Virginia house using 14,000 kWh per year: (Is your house average sized?)

  • Compared to power plants burning fossil fuels:

  • 5 tons of coal not burned (and not mined) per year, and the corresponding reduction in greenhouse gas emissions. (EPA greenhouse gas calculator)

  • or

  • 140,000 cubic feet of natural gas per year (which is mostly what Dominion uses)

  • Multiplied by the life expectancy of the panels (at least 25 years), that is a lot of fossil fuels not burned!

  • Compared to buying “renewable” energy from your power company

    • Land use - Many if not most solar projects by power companies are built on undeveloped land which could have been providing wildlife habitat. Roof arrays, by contrast, are utilizing space that is already fully developed.

    • Community resilience - If you get a battery, your building can provide recharging services and shelter for your neighborhood in times when the grid goes down, something that is likely to happen more and more from extreme weather events. Puerto Rico’s terrible experience has shown us the value of a decentralized electricity system.

    • Less stress on the transmission lines. The more power sent through those lines, the faster they degrade and the higher the risk of starting fires.

    • Also, “renewable” energy sold by Dominion is not what you think it might be - see this critique of “Green Power for Suckers.”


How many panels you will need

  • You don’t have to offset all your power use if you don’t want to. You could put up a smaller array now and expand it later. Or perhaps you only have enough appropriate roof space for a small array. It is still worth it.

  • You are not permitted under Virginia’s current restrictive laws to make a profit by selling your unused electricity to the power company.

  • To offset 100% of 14,000 kWh per year, you would need roughly 24 of the 400-watt or 30 of the 320-watt panels. This might cost $20,000 - $30,000 or so in upfront costs (minus the tax credit). Each panel is approximately 17.5 square feet.

How they work

The panels collect photons from the sun and convert them to Direct Current (DC). The inverters convert them to Alternating Current (AC). (The newer microinverters decentralize that to each panel). The system then balances out the input be either pulling electricity from or pushing it to the grid or a battery to deliver the same volts at all times to your house. (Fluctuations would be bad for some electronic equipment.)

How they are monitored

You can check your meter monthly to make sure the system is behaving as expected, or you can purchase an electronic monitoring system that allows you and the company to see which panels are producing how much electricity at any given time. Either internet or cellular access is required for remote monitoring.

How they are warrantied

Each system comes with several different warranties:

  • Installation: Installers warranty their work, typically for 10-12 years. Some installers have their own in-house maintenance division.

  • Solar panels: two separate warranties for 20 or 25 years, depending in part on the efficiency and durability of the panels.

    • Power output - Efficiency falls over the years. At 20 or 25 years, the warranty will be for the expected efficiency (85-92%)

    • Workmanship

  • Inverters (or microinverters): The warranty depends on the company.

Who manufactures them

There are numerous manufacturers, most of them overseas. You can compare their corporate good citizenship on the Solar Scorecard website.

Interacting with the grid

You are allowed to install a solar roof array that would up to150% of what you consumed in the last year. Any excess that you produce during the day is fed back to the grid, running your meter backwards. At night or on cloudy days, you receive power from the grid. If you installed a system designed to produce 100% of your power, your electricity bill will come down to the monthly connection fee and taxes (around $10-$15).


You do not have to have batteries, which cost about $12,000 apiece installed (and you might need more than one). If you do have a battery, you are allowed to become independent of the grid and have power during blackouts. (Without a battery, your system automatically shuts off during blackouts so that electricity will not flow out of your house and electrocute line workers.)

Financing options

Besides digging into your savings (which would give you the best financial returns if you have the money), there are a couple other options.

  • Investors: Someone else (a person or a company) could pay for and own the installation, taking the tax credit and depreciation, and selling the electricity to you. You could then later buy the system from them (but no sooner than five years.) However, these Power Purchase Agreements are not allowed on private residences by Dominion - our legislators need to step in to change that restriction.

  • Loans:

    • For homeowners: This is similar to a home improvement loan, except you are getting a return on your investment. Read about solar loans here. When you see ads for solar with “no upfront costs to you,” they are talking about a loa, they way car dealerships give you car loans. Interest rates are low at the moment, you may have noticed..

    • For commercial entities: The Fairfax County Board of Supervisors has contracted with the Virginia PACE Authority to administer C-PACE loans for businesses (which includes faith communities and other non-profits, and dwellings that have five or more units) investing in energy saving improvements to their buildings. The financing is tied to the building and does not come due just because you sell the building - it conveys via a lien on the property.

To be able to take the full tax credit, you probably need to complete all components of the project in one tax year.

Your roof


  • If you have a new roof, go for it right away!

  • If you will need one relatively soon, go for it now! The environmental cost of a few hundred pounds of roofing material is miniscule compared to the environmental costs of electricity produced by power plants.

  • If you are maybe ten years into your roof, do it anyway. It will cost you several thousand dollars to have the system taken off and reinstalled when you replace your roof, but you are still likely to come out ahead financially.

Type of roof

Solar can go on top of any kind of roof except probably slate.

Asphalt shingles

  • Low upfront cost, high long-term cost. Usually last 15-30 years.

  • Sometimes leak.

  • Good at keeping in heat during the winter, but one of the worst types of roofing for keeping cool during summer.

  • The roof will need to be penetrated by the bolts that attach the solar array to the rafters. There is a small risk of causing leaks (which would not be covered by the warranty, though probably covered by your homeowner’s insurance.)

Metal roofs

  • High upfront cost, low long term cost. Often backed by 50-year to lifetime warranties.

  • Reflect the sun and reduce air conditioning costs.

  • Highly unlikely to ever leak. Not damaged by moss or raccoons.

  • Solar panels are clipped onto the seams and do not penetrate the roof.

  • Since the roof lasts so long, you don’t need to worry about paying to reinstall the solar panels when it comes time to replace the roof.

What is not permitted or available in Northern Virginia as of March 2020

  • Installing arrays larger than what would be needed to provide 150% of past bills.

  • Selling electricity back to the grid

  • Community solar - so far, this has been hampered by lack of funding

  • PACE loans for single-family residential, multifamily residential (less than five units), or condominiums


Forest Road


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