Maryland recently passed legislation which will allow residential-scale in-state solar water heating systems (SWH) installed on or after June 1^st 2011 to sell SRECs into the MD SREC market.  Eligible systems will, at a maximum, be able to produce 5 SRECs per year. The law does not go in to effect until January 1^st 2012, so even if the system is installed now it will be another few months before they can monetize their SRECs. The bill states that eligible SWH systems are those that are not used solely for heating a pool or hot tub and are either metered by a device that meets the standards of the “International Organization of Legal Metrology” (OIML) or be OG-300 certified.

Another requirement is that the SWH collectors (the product that captures the sun’s heat) must be a “glazed liquid-type flat-plate or tubular solar collector by the OG-100 standard of the Solar Ratings and Certification Corporation (SRCC).”

Because SWH systems produce heat and not electricity, output is measured in British Thermal Units (BTUs) and not kW-hrs. In order for these systems to produce SRECs equivalent to their PV-system counterparts, they must be certified and metered in a way that can allow for accurate measuring and unit conversions. By multiplying each BTU by a conversion factor of .000293, one can determine the kWh equivalent production from the system. As a point of reference, a single a 21 ft² flat plate solar thermal collector located in Baltimore, MD that has a conversion efficiency of 60% may produce as many as 2 SRECs per year.  Conversion efficiencies and BTU output will vary depending on the type of SWH panel used.