We had been interested in purchasing solar panels for a long time, but we were not sure how to evaluate the information we received from various installers. Then, last spring, a notice was posted on the neighborhood listserv about a solar-buying cooperative, Solar United Neighbors (SUN). We attended a meeting in Rockville and left feeling confident that we had found the way forward.
SUN is a nonprofit group. Every year, it organizes temporary co-ops of potential buyers in a number of geographic areas. This year you can still join the Montgomery County buyers’ co-op as late as August 31 by going to coops.solarunitedneighbors.org/ coops/montgomery-county-solar-and-ev-charger-co-op.
There is no fee to join the buyers’ co-op and there is no obligation to purchase and install solar panels. The obligation associated with joining the co-op is that you provide the co-op with your telephone number. The co-op will pass on that number to the company the co-op eventually chooses as its provider. When the company calls, you can:
According to its web page, SUN began in 2007 when a son of Anya Schoolman, a D.C. resident, and his friend saw Al Gore’s movie “An Inconvenient Truth.” At first glance, an investment in solar seemed to be too expensive. But Anya wondered if a bulk purchase might make solar affordable. She got the boys to knock on doors in their neighborhood. Eventually, 45 neighbors purchased solar panels with the first group, the Mt. Pleasant (D.C.) Solar Cooperative. Since then, they have organized buyers’ co-ops in 12 states and the District of Columbia, helping 4,600 families invest more than $93 million in solar panels.
The first step in the buyer’s co-op process is to attend an information meeting where a SUN representative answers questions regarding financial and technical issues related to purchasing solar panels and explains how the co-op works. The financial questions include how much a typical solar installation costs, the impact of state and federal credits on the purchase, and whether there are alternatives to paying the entire purchase price immediately. The table below, provided by SUN, illustrates the relationship between the size of an installation, the purchase price, and state and federal credits.
|Example of Typical Design (kilowatts)||4kw||8kw|
|Average MoCo Solar Price @$2.70 per watt installed||$10,800||$21,600|
|26% Federal Tax Credit||–$ 2,800||–$ 5,600|
|Maryland Residential Credit||–$ 1,000||–$ 1,000|
|Net Cost||$ 7,000||$15,000|
|Estimated Lifetime Savings||$22,100||$44,100|
The Net Cost is the sum of the initial cost less the federal and state credits. The life-time savings are based on the amount each panel is expected to generate over the life of the panel. Each panel should generate electricity over a 25-year period. The productivity of each panel is estimated to reduce somewhat over time. The life-time savings also assumes that the cost of purchasing electricity from Pepco will increase over time. Therefore, even though the table shows an illustrative profit, your profit could easily be greater or less than the profit shown if any of the assumptions used to generate the example changes.
On SUN’s web page there is a section on frequently asked questions. I am providing their responses to three technical questions that were important to me.
The first technical question is: How does solar electricity work? Solar panels are made up of photovoltaic (PV) cells made of silicon. When the sun’s rays hit them, these cells convert sunlight to electricity. Individual cells are wired together to form a solar panel. Panels are typically three feet by five feet. The electricity produced by a single solar panel is not enough to power a home or business, so multiple panels are needed. The number of panels varies by installation, but every solar system (also called an “array”) will include a series of panels mounted and wired together.
The electricity generated by solar panels takes the form of direct current (DC). However, most appliances and electricity-consuming objects (called “electric load”) require alternating current (AC). To convert the solar electricity from DC to AC, an inverter is needed. Once the electricity is converted to AC, it is connected to your home’s electric network. When your generation is less than your usage, you will purchase the difference between generation and usage from Pepco. When your generation is greater than your usage, you will sell electricity to Pepco. The electricity that you sell is credited at Pepco’s billing rate to you. This process is called “net metering.”
The second question is: How large a system should I purchase? The size of your optimal solar array will be influenced by many variables. Your installer will estimate how many panels can fit on your roof given its footprint and shade susceptibility to determine the ideal size of your system. If the size of your roof is limited (meaning fewer panels can be installed), installers can compensate by offering high-efficiency panels. Installers will also use geospatial data to determine the optimal system size for your property, as roof orientation to the sun and climate factors will affect how much electricity your system produces. Then, of course, there is your budget. Installers work closely with clients to maximize the amount of solar they install for the customer’s budget.
A third basic question is: Will my system operate when Pepco shuts down? The answer is no. The power shuts down in order to protect Pepco’s repair crew that will be trying to fix the outage. If you want your solar panels to continue producing electricity even when the grid goes down, you will need to pair your solar array with batteries.
Once the financial and technical questions were answered at the meeting, the SUN representative explained that the next step would be to solicit bids from local solar panel installers. Two companies responded to the request. A group of about ten co-op participants (along with the SUN representative) met to review the responses. Our review process focused not only on price but also on whether the installer would guarantee completion by December 31, whether the installer would replace roofs if necessary, and how the installer would help the customer obtain the necessary approvals from Pepco.
The group picked a winning bidder in the middle of the summer. The winning bidder then called all of the members of the co-op to set up a time to discuss each member’s individual needs. The sales representative showed up at our house with a satellite picture of our roof that included our roof’s dimensions and some knowledge of the shading impacts of nearby trees. The sales representative asked to see our Pepco bills to determine how much electricity we were using and what price we were paying, and he also asked about our budget. With that information, his software generated a design for solar panels for our roof, the estimated output of those panels, and how much we would save over the next 25 years.
For the skeptical person who might believe that a salesperson would over-estimate the amount of electricity that our system could generate, there is an easy way to double check that estimate. The National Renewable Energy Laboratory has a calculator on its web page (pvwatts.nrel.gov). I entered the capacity of the system we were purchasing and our street address and the calculator returned the amount of kilowatt-hours our system would generate. That estimate was very close to the estimate provided by the salesperson.
Our system was installed in October 2019 and was approved for generation in November. The output of any solar system obviously depends on the number of daylight hours in a month and whether its is sunny or cloudy. In December, our average daily output was 16 kWh, with a low of 3 kWh and high of 29 kWh. By April, our average daily output had increased to 40 kWh, with a low of 7 kWh and a high of 67 kWh. In April, our solar panels generated more electricity than we used.
The co-op saved us more than 20 percent off the installed cost of our solar panels. We know this because, in January 2019, before we attended our first co-op meeting, we had requested an independent estimate from the same company that the co-op ended up choosing that fall. That early estimate was 20 percent more than we paid through the co-op. Given the time needed for decision making, installation, and inspection, if you wish to have the job finished by December 2020, now is the time to begin.
[Loube, an economist who testifies on behalf of public interest groups before state public utility commissions, has lived on Cavalier Drive almost 31 years.] ■
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