All code-compliant solar systems include two additional components: meters and disconnect switches.
Meters are used to measure electrical production and consumption. The meters that measure electrical production by a PV (Photovoltaic) system and consumption by you and your family at any given time, providing an instantaneous picture of energy production and consumption. They are typically located on the inverter itself or in a separate location, situated in a convenient place for ease of monitoring.
Meters typically track electrical production and consumption in amps or amperes. More sophisticated meters, however, measure long-term electrical production—that is, the total energy produced and consumed over long periods of time. As a result, they typically keep track of production and consumption in kilowatt hours.
If an inverter doesn’t come with a built-in meter, you can buy a separate unit and connect it to your system.
Grid-connected PV systems also require one — sometimes two — standard utility electrical meters. These large, tamper-proof glass-encased meters are installed by the utility company. They keep track of monthly energy production and consumption so the utility can bill you at the end of each month. Grid-connected solar electric systems also contain a couple of safety switches, called disconnects. Disconnects enable homeowners or service personnel to shut power down to prevent electrical shock when working on the system.
As shown in Figure 7-4, a DC disconnect is located between the solar array and the inverter. It is used to terminate the flow of electricity to the inverter. The other disconnect, the utility-accessible AC disconnect, is located between the inverter and main service panel. It is used to shut off the flow of electricity from the inverter to the household circuits and the grid. The AC disconnect is a safety switch utility workers shut off if they need to work on the electric lines to your home or in the neighborhood.
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