An Introduction to PV Systems
3 Types of Residential PV Systems
Grid-Tied
Grid-tied is the least expensive. A grid-tied system is comprised of PV panels (mounted on the ground or rooftop with fixed or tracking mounts), conduit and wire, an inverter (converting DC to AC), a DC breaker, an accessible and lockable disconnect switch, and approval from the local power utility. Grid-tied systems offer home owners a means of offsetting power consumption through the generation of power during the day* which is pushed (sold) back to the power utility, while nighttime power is purchased from the utility.
Grid-tied is the least expensive. A grid-tied system is comprised of PV panels (mounted on the ground or rooftop with fixed or tracking mounts), conduit and wire, an inverter (converting DC to AC), a DC breaker, an accessible and lockable disconnect switch, and approval from the local power utility. Grid-tied systems offer home owners a means of offsetting power consumption through the generation of power during the day* which is pushed (sold) back to the power utility, while nighttime power is purchased from the utility.
Grid-Tied / Battery-Backup
Grid-tied / battery-backup is more complex in that some or all of the house-hold wiring must be routed through the inverter and to the batteries in order that if power is lost from the utility, the battery backup system can take-over for a limited period of time. Routing the entire house is actually simpler than just a portion, but also requires an appropriately sized battery bank and vented, temperature-controlled enclosure. Batteries require some maintenance to ensure long life, with 5-10 years being typical for properly maintained systems. A modern, properly configured inverter will prolong the life of a battery array, ensuring full charge while placing a limit on the lowest level.
Grid-tied / battery-backup is more complex in that some or all of the house-hold wiring must be routed through the inverter and to the batteries in order that if power is lost from the utility, the battery backup system can take-over for a limited period of time. Routing the entire house is actually simpler than just a portion, but also requires an appropriately sized battery bank and vented, temperature-controlled enclosure. Batteries require some maintenance to ensure long life, with 5-10 years being typical for properly maintained systems. A modern, properly configured inverter will prolong the life of a battery array, ensuring full charge while placing a limit on the lowest level.
Off-Grid
Off-grid is the most expensive in that the number of panels and batteries increases considerably in order to fully compensate for all the power requirements of the home. In most cases, if running a full, modern home, we are looking at ~3KW (3,000 watts) of power from the panels and a substantial battery system capable of running the house for 2-3 days. This configuration is typically not done unless the house is in a remote location. Generally, power utilities will extend their lines up to ¼ mile just to get a new customer. Beyond that, the cost is about $30,000 per mile. So if you live more than 1/2 mile from the nearest power line, the economics support going off-grid.
Off-grid is the most expensive in that the number of panels and batteries increases considerably in order to fully compensate for all the power requirements of the home. In most cases, if running a full, modern home, we are looking at ~3KW (3,000 watts) of power from the panels and a substantial battery system capable of running the house for 2-3 days. This configuration is typically not done unless the house is in a remote location. Generally, power utilities will extend their lines up to ¼ mile just to get a new customer. Beyond that, the cost is about $30,000 per mile. So if you live more than 1/2 mile from the nearest power line, the economics support going off-grid.
* It is not necessary to offset 100% of the power. The idea is to reduce peak power use as much as is possible, reducing the overall electrical bill. If your utility allows "time of use" pricing, wherein power used during peak hours (usually mid-day) costs more than during off-peak hours, payback time for the system is greatly reduced. Peak hours are when you’ll be making electricity, thus offsetting your use of the more expensive utility electricity.