Grid-Tied (Net-Metered) Photovoltaic Systems

Click here for more info about the legal aspects of net-metering in New Mexico.

Sharmon Southeast view

The system pictured at right is one of several state-of-the-art grid-tied, "net-metered" photovoltaic system installed in Santa Fe. If you want to see such a system in the Santa Fe area, we suggest you call Positive Energy Inc at (505)424-1112, who has installed several of them.

This system's Sunny Boy brand inverter inverts high-voltage DC solar electricity into conventional AC electricity that is synchronized (net-metered) with the electrical grid, and integrates this power with the grid to offset the electricity used by the home. When the PV system is producing more power than the home is using, the electrical meter on the home actually spins backwards, effectively "banking electrons" for future use. The solar electricity is credited against the home's electrical bill at full retail value.

This system does not have batteries, so it will not provide electricity during a utility outage. However, this system's batteryless approach has distinct advantages over off-grid or battery-based systems, including lower cost, by about 20-30%; higher efficiency; very little maintenance; more environmentally friendly without batteries; and it's available to nearly everyone. It is also modular, in that it allows you to start small and add additional capacity as funds and wishes allow.

Sharmon Phil & Dan with Sunny Boy

This particular system consists of ten BP 150-watt PV modules on two seasonally-adjustable racks, a Sunny Boy 2500-watt inverter with display, and all proper disconnects and safety equipment. Prefabricated standoffs were installed on the garage roof during a recent remodel, prior to the application of foam insulation and gravel. The array and racks were mounted to the standoffs after the roof was completed, allowing a neat and economical installation. A crew of three PV professionals (two of whom, Phil Undercuffler and Dan Rice, are pictured at right) installed the complete system in one day!

The system may be expected to supply approximately six kilowatt-hours of electricity per day year-round. Actual output of the power system varies depending on season, time of day, sun angle, array temperature, localized shading from trees, and air clarity. The total installed cost of this system including all equipment, installation materials, labor, tax, permits and PNM interconnection fees came to $15,600. Smaller grid connected PV systems start around $8,000. Positive Energy to date has successfully completed interconnected PV systems with four New Mexico utilities to date: PNM (Santa Fe/Albuquerque area), Mora-San Miguel Electric Cooperative (Pecos area), Jemez Electric Cooperative (Espanola area), and Kit Carson Electric Cooperative (Taos area).

Grid-Tied Systems With Batteries

Benson Array from roof
Benson Straightened Battery Box
Benson Power equipment on wall finished

The array pictured pictured at right is another grid-tied (net-metered) photovoltaic system, but this system has batteries as well (pictured below), which is accomplished using a "Multi-Mode" inverter (also pictured with the electric meter and other components below). With batteries, the power system can provide backup power to run their entire home during a utility outage of up to several hours. The system is essentially maintenance-free, through the use of sealed gel cell batteries and a fixed PV array.

The owners of this system have a strong interest in and passion for renewable energy. Their former home was completely "off-grid", getting all of its power from PV and wind power. As such, they had already learned how to live on far less electricity than a conventional home. They have integrated significant energy conservation measures into their home, including compact fluorescent lighting, refrigeration, and energy efficient clothes washing. They use natural gas for cooking and heating, rather than electricity. Due to these careful load management efforts and energy efficiency measures, this system produces nearly 100% of their energy needs. In May, PNM (an electric utility in New Mexico) sent them a bill for one kilowatt-hour of electricity for the entire month!

The systems owner's moved into town from the Lone Butte area in 2001. This system was completed in April of this year by Positive Energy Inc. of Santa Fe. The power system consists of eight BP 150-watt photovoltaic modules on fixed roof racks, an AES Multi-Mode three kilowatt inverter, four 12-volt 100 amp-hour sealed batteries in an outdoor battery enclosure, and all proper disconnects and safety equipment as required by the National Electrical Code and PNM. This power system supplies approximately 4.7 kilowatt-hours of electricity per day. The total installed cost of this system, including all equipment, installation materials, labor, tax, permits and PNM interconnection fees is $20,500. Smaller grid connected PV systems start around $8,000, including installation by Positive Energy.