Some rebate programs (especially production-based incentive programs) require an additional production meter to track output. An independent meter may also be required to count your solar renewable energy credits (SRECs or “green tags”), where organizations may pay system owners for the right to claim ownership of every green kilowatt-hour the system produces in addition to the net-metering credits earned with the local utility company.
A utility-grade meter installed on the output side of the inverter(s)—before they reach the distribution panel—is the simplest method and usually requires a standard utility-type meter base. These meters are affordable, durable, and easy to read—so long as you’re standing right in front of them. Most SREC/green tag incentive programs allow these meters, but they require the added effort of regular, manual data recordings, which need to be faxed or e-mailed to the incentive program’s coordinating agency.
A more sophisticated, less time-consuming approach is to employ a third-party data monitoring system (see Access) that can record the system’s performance independent of the inverter and transmit the information to the Web—with minimal effort from the system owner. Solectria offers their revenue-grade option specifically for this purpose. Additionally, some inverter companies, such as PV Powered, offer third-party data monitoring packages pre-installed within the inverter. These operate independently from the inverter, while saving space and installation time, since system monitoring hardware doesn’t have to be installed separately.
One company that took the watchdog concept to market is Fat Spaniel Technologies (FST), one of the leaders in third-party monitoring. Along with precise, automated SREC monitoring and reporting, their system presents useful energy information—often in an entertaining format. For instance, one report translates energy values in terms of cups of coffee that could be brewed with the solar energy produced. And like many of the inverter-direct monitoring products, FST offers other advanced features, such as data-syncing with environmental sensors to record wind speed, irradiance values, ambient temperature, and PV cell temperatures. These values are graphed alongside production values to display real-time performance analyses of the system’s modules and inverters. More committed conservationists will also appreciate FST’s ability to monitor a home’s energy usage throughout the day and identify specific load-profile patterns that can then be tweaked to further improve a home’s energy efficiency. (MSRP: Call FST for pricing.)