U.S. Department of Energy Energy Efficiency and Renewable Energy

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November 05, 2012
Q.

What fundamental roof information should I get from my municipal facility managers in preparation for a solar PPA? -Todd

SunShot Solar Outreach Partnership

The SunShot Solar Outreach Partnership has been tasked with helping accelerate adoption of photovoltaic (PV) solar at the local level by providing timely and actionable information to local governments.

A.

As you suspect it is critical to ensure that your rooftops are structurally sound enough to support the weight of a solar photovoltaic (PV) system under various weather conditions. Furthermore, you want to ensure that PV systems are situated to maximize energy generation. When evaluating rooftops to be included in an RFP you may wish to consider asking the following questions of building facility managers:

  • When the roof was last repaired or replaced?  You'll want the roof to last at least 15-20 years. Be sure that the roof meets the most recent building codes for snow and wind loading requirements.
  • Does the roof meet current snow and wind load requirements?
  • What direction does the roof face? You'll want to prioritize south-facing rooftops.
  • Is the roof shaded? You'll want to select rooftops without excess shading from vegetation, near-by buildings, or from large HVAC equipment or other structures already located on the roof.
  • Is there enough space for the desired size system? How much roof space is available for PV? You can use NREL's In My Back Yard to estimate available roof space or you can use the SolOpt tool.
  • Is the building an historic building or in a designated historic district? If so, there may be some restrictions both in terms of aesthetics or building design that may limit the ability to install a solar system.
  • Is the rooftop within an "area network" of the utility? Some cities such as Boston and New York have areas within their grid that may be limited in terms of the amount of distributed generation allowed by the utility.

Respondents to the RFP should be required to ensure that the installation will not impact rooftop integrity, or violate any existing warranties or insurance requirements of the buildings. Any selected contractor should obtain written certification of existing warranties or provide their own warranty of rooftop integrity. Our partner, The Solar Foundation has an excellent resource on developing a solar RFP.

In addition, members of the SunShot Solar Outreach Partnership have assisted cities and towns in Massachusetts in evaluating solar RFPs.  If you are interested in applying for an RFP review please contact us at solar-usa@iclei.org.

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