The system consists of two 1.2KW sub-arrays (2.4KW total capacity) each with its own grid-interactive inverter. The output from both of these inverters is connected to a Capitol electric service panel. The photovoltaic array is mounted on fixed hardware and includes a grid-interactive inverter that ties the array output to the electrical service for the Capitol Building. The system, on the southeast corner of the Boiler Plant Building, is highly visible to several other state agencies, as well as from Roberts Street. The building lies along the route of the Montana Historical Society Tour Train, which serves thousands of visitors each year, and the array will no doubt be featured in the tour. 

Designed and installed by Independent Power Systems, Inc., of Bozeman, Montana, the system faces south with a fixed tilt of approximately 45 degrees. Estimated annual output of the system is 3,679 KWh. It is expected to have a useful life of 20-plus years and should require little maintenance other than periodic cleaning of the array and tightening of electrical connections. The General Services Division will maintain the system and will log the power output on a monthly basis over a period of two years.

Major system components include:

• photovoltaic modules with a combined total output of 2.4KW
  
• array mounting structure, ballasted pan type
  
• fused disconnects, lightning protection system, and miscellaneous electrical components
  
• grid-interactive inverter with system monitoring capability

Total installed system cost was $32,068. Estimated electric cost savings from the project: $343/year.

Project funding came from Montana Power Company's Universal System Benefits fund ($26,522) and the State Department of Environmental Quality funds ($5,546). The project was installed in October 2001.