One-Roof Solar Evaluation

November, 2011

The cost to install residential solar panels in the Washington DC area has dropped significantly in the last two years.  DC Solar United Neighborhoods, a consortium of cooperatives, has completed a cost comparison by inviting vendors to bid on the same job.  Four vendors participated in the bidding (Lighthouse Solar, Solar City, Solar Solution and Astrum Solar), while several other vendors completed an online survey . Our goal in presenting this information is to provide as much relevant and unbiased information as possible to help you choose the installer that’s right for you.  We hope you find this information helpful.

Meet the Installers

To provide basic information about installers in the area with which DCSUN is familiar, we conducted a survey. The questions are meant to give you a general understanding of each installer's capabilities and services. We asked installers to respond on topics such as how long they've been in business, how much work they've done in the District, what kind of certifications they have and what kind of financing they offer. For survey results, click the link next to each participating installer in the directory below.

Helpful Survey Terms

DDOE - DC Department of the Environment
NABCEP - North American Board of Certified Energy Practitioners
RISE - Roof Integrated Solar Energy
SREC - Solar Renewable Energy Credit

One-Roof Reference Bidding

Four companies chose to compete in DC Sun’s One Roof Evaluation bidding process. Participating installers were asked to come to the residence of the same Capitol Hill homeowner and provide a bid. Besides comparing prices, having them all bid to install a PV system on the same roof allows one to compare equipment, size, installation and other options.

Lighthouse Solar, Solar City, Solar Solution and Astrum Solar submitted bids in the order listed for purchasing a PV system. Solar City submitted three leasing options for the same PV system. Astrum Solar submitted bids for three different PV systems, varying the system size and installation method. Please note that our reference bid project only represents a snapshot in time. Market conditions, equipment pricing, and financial incentives are all subject to change over time.

Here are some of the key findings from this process:

  • Gross system cost (before any incentives) for purchasing a system averaged $25,061, ranging from $19,382 to $34,320.
  • Net system cost (after tax and other incentives) for purchasing a system averaged $12,854, ranging from $9,922 to $16,784.   The reduced net costs factor in Federal tax credits and solar Renewable Energy Credits (sRECs) that vendors will help you leverage.
  • For the lease options, the Initial System Cost averaged $3,639, ranging from $0 to $7,278. Two of the lease options had annual payments, averaging $44/month, ranging from $516 to $816 per year.
  • Simple Payback for purchase averaged 13 years, ranging from 12 to 15 years. For leasing, the average was ~11 years, excluding the $0 down option.
  • Internal Rate of Return for purchase averaged 5.8%, ranging from 4.6% to 7.5%. For leasing, the average was 10.0%, excluding the $0 down option.
  • Reduction in the home's electric use ranged from 92% to more than 100%. A smaller system can be installed if the home is fully weatherized and has energy efficient heating, cooling, lighting and appliances.
  • DC SUN suggests that weatherization be done prior to, or in conjunction or directly after you have completed your  solar installations.  If your solar installation is linked with significant roof work-- you should definitely take care of insulation and sealing the attic at the same time. DC SUN also recommends that systems not be sized greater than 100% because current DC laws do not allow you to take advantage of “overproduction” that occurs over a year’s time frame -- unless you are planning on buying an electric car in the near term that would consume your energy surplus.
  • This analysis does not take into account the presence of any DC solar rebate.

To see the bid results click on the link next to each participating installer in the directory below or go here.

I Want to Run The Numbers Myself!

Great! To play with the numbers and tailor them to your situation, check out this spreadsheet [Link to Andy's Spreadsheet].

Which Installer is Right for Me?

When looking for an installer, we recommend you get 2 to 4 quotes to compare. Getting quotes from more than one installer will help you better understand your needs and what you're looking for in an installer. One size definitely does not fit all. Choosing any contractor is a very personal experience. Don't be afraid to ask questions and ask your installer to explain things to you. Whether you're buying your system or leasing it, you're choosing a system that's going to last for 20-30 years. You should feel comfortable with your choice.


Installer Directory

Below is a list of all the installers in the area which are known to DCSUN. For a complete list of installers approved by DDOE, please see their list under "District-Area Renewable Energy Contractors and Installers".



 Survey **

 Reference Bid

 Astrum Solar



 Aurora Energy



 Capital Sun Group



 Continuum Energy



 Kenergy Solar



 Lighthouse Solar



 Maggio Roofing



 Solar City



 Solar Solution



 Standard Solar



 Volt Energy



 WDC Solar



** Download the full survey responses here.

Thinking about going solar? Tell ‘em DC SUN or your local solar coop sent you!  Many local installers will make a donation to DC SUN’s Community emPOWERment Fund if their customer is a member of DC SUN. Money in the fund goes to support solar projects for non-profits, churches, and other community organizations. So, when you talk to an installer, tell ‘em DC SUN or your solar coop sent you! (Note: DC SUN is 100% installer neutral. Installer participation in the emPOWERment fund does not constitute an endorsement of the company.)