-How Solar Power Works
-Why Go Solar?
-Getting Started
-Solar Thermal Systems

How Solar Power Works
Solar electric systems, also known as photovoltaic (PV) systems, convert sunlight into electricity.

Solar cells—the basic building blocks of a PV system—consist of semiconductor materials. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms. This phenomenon is called the “photoelectric effect.” These free electrons then travel into a circuit built into the solar cell to form electrical current. To see a simulation of the photoelectric effect, please view our Solar Power Basics animation. Only sunlight of certain wavelengths will work efficiently to create electricity. PV systems can still produce electricity on cloudy days, but not as much as on a sunny day.

The basic PV or solar cell typically produces only a small amount of power. To produce more power, solar cells (about 40) can be interconnected to form panels or modules. PV modules range in output from 10 to 300 watts. If more power is needed, several modules can be installed on a building or at ground-level in a rack to form a PV array.

PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day.

Because of their modularity, PV systems can be designed to meet any electrical requirement, no matter how large or how small. You also can connect them to an electric distribution system (grid-connected), or they can stand alone (off-grid).

Source: U.S. Department of Energy

Why Go Solar?
1.    Cost of System—prices have dropped 30-40% during the past year.
2.    DC Rebate–$4,500/kw (see District Department of the Environment [DDOE] website for details)
 3.   Federal Tax Credit—30% of total cost
 4.   Sale of Solar Renewable Energy Credits (SRECs)
Not electricity but the green value of the power you produce. Sold through an aggregator or online exchange to Pepco to meet their requirements of having energy on the grid come from renewables.
 5.   Energy Savings-from Net Metering
The actual energy you produce reduces your Pepco bill on a 1:1 basis. You can roll over excess generation from month to month (like rollover minutes) but you do NOT get paid for excess generation (feed in tariff).

The numbers presented in the table below are projections only and are intended to demonstrate the potential positive returns. They represent best estimates given current information. The values are subject to change, and in all likelihood will change. The values are not guaranteed.

Table below is based on a 3.0 kW system

Total cost (1) $15,000
Less DC rebate (2) ( $4,500)
Your upfront cost $10,500
Savings and Credits:
1-time federal tax credit (3) $5,940
Annual energy savings (4) $400-$1,000+/year
Annual sale of renewal energy credit (5) $1,000/year or $4,800 up front payment
Lifetime 30-year energy savings, assuming ~7% annual increase $30,000+

(1) Actual cost will depend on specific system; some homes require roof work prior to installation. Cost can be financed or paid in cash at installation. Source: Washington Post, 9/3/11.
(2) DC rebate plan provides cash to homeowner prior to payment to installer. Rebates are $1.50/w up to 3000 watts, $1 for each of the next 7,000 watts (up to 10,000 watts), and $.50 /watt up to 10,000kw. See DDOE Web site for details:,a,1244,q,461562.asp.
(3) Tax savings/credits estimates should be discussed with your individual tax advisor. Federal Tax credit would be sought when filing tax returns for the year of the installation: for installation in 2010, tax credit would not be received until 2010 return is filed in 2011.
(4) Energy savings are based on current Pepco rates, and 7.17% annual increases. The previous 17-year average annual increase has been 3%, while over the previous 5-years the average annual increase has been 13%. If the Pepco rate increases are less than 7% estimate, then energy cost savings will be less; if rates rise more than 7%, then energy cost savings will be greater.
(5) Rate for first 5 years locked; additional years to be negotiated. Also, from some companies an upfront 10 year payment is available at $1600/kw installed.

Getting Started
1.   Complete the 2010 DC rebate pre‐application online.,a,1244,q,461562.asp. This will ensure you get on the waiting list for a DC solar rebate. It is a bit confusing but don’t worry. Write in the name of your Solar Coop as your installer. Fill out the size of the system as 4kw. You probably will not need that much solar power, but you can reduce it later. Answer all the questions, but don’t worry if the answer is no. It doesn’t matter.

 2.   Select an Installer*
Get three estimates for your solar installation. You can talk to CPEC members and get their recommendations. Some installers offer discounts to CPEC so be sure to ask them about these savings.

Key Considerations for Choosing an Installer:

  • price
  • track record
  • experience
  • have they worked in DC before?
  • how long have they been in business?

One of the key differences between installers is their approach to attaching the panels on your roof. You want to make sure that the system will not cause leaks in the roof. Your roof needs to be in good condition before you begin installation. The installer must be on DDOE’s list of approved in order for you to be eligible for a DC rebate.

3.   Once You Select an Installer and Sign a Contract.
The installer will guide you through the full rebate application process, and the permit process. Make sure the installer is taking responsibility for communications with DDOE, DCRA, and Pepco as part of the contract.

*CPEC does not endorse any products or services.

DC Energy Office,a,1244,q,461562.asp.
Learn about the city’s solar rebates and access the online pre-application.

Calculate How Clean Your Energy Is

Database of State Incentives
Access state incentives for renewable energy.

Solar Renewable Energy Credits (SRECS) or try
Learn how to sell your SRECs and great background info.

Solar Thermal Systems
Effective, Wednesday, April 11, 2012, and in accordance with the Clean and Affordable Energy Act of 2008, the District Department of the Environment Renewable Energy Incentive Program (REIP) will provide financial incentives to eligible applicants in the District to help install Solar Thermal systems.

Eligible projects may include, but are not limited to, the installation of systems on single and multi-family dwellings as well as commercial buildings and institutional organizations.

Renewable energy sources such as solar, wind, geothermal and/or biomass can help to reduce dependence on a shrinking supply of fossil fuels and greenhouse gases that contribute to climate change.

We encourage you to apply to the program. Please visit for more information.