On-site power generation increases security through energy independence and control of the power source. A PV system generates on-site power from solar energy with no fuel cost or GHG emissions. If a PV system produces more electricity than the facility needs, surplus power can be sent or sold back to the grid provider through ‘net metering,’ and some utilities may provide green power incentives for PV installations, or reduce electricity rates for facilities with PV systems. PV systems are typically modular, and installation can be phased.

There are three common types of PV installations:

• Battery systems charge direct current (DC) batteries, which are available for use during the day or night, but have high maintenance
• Grid-connected systems connect directly to the facility power system and supplement the base power source (utility or generator).
• Simple feed systems connect directly to the facility power system and are designed to operate independently of the electric

To determine the potential for installing PV systems on a site:

• Look online for solar insolation maps (Resources: . Note that PV systems are most cost-effective on sites with an average daily solar insolation of at least 5 kWh/m².
• Also consider that sites with lower solar insolation but electricity rates higher than $0.24/kWh are also good
• Consider the following when identifying locations for PV modules (see Energy: Thermal Solar Water Heating)
• PV panels can be located on building roofs or walls or as free-standing, ground-mounted arrays that may also serve to provide solar shading for windows, walkways, and parking areas.

• Installing panels with at least 10% tilt can reduce maintenance and cleaning
• Installing thin-film cells on curved or irregularly shaped surfaces greatly increases installed cost, thus reducing payback