Solar panel systems are not all created alike. Just because homes have a set of solar panels on the roof, it doesn’t mean that they all are operating similar systems by any stretch of the imagination.
Primarily, there are two types of solar installations on residential homes – grid-tied solar, and off-grid solar, and we’ll look at both types in this article.
First of all, however, it’s important to note that regardless of how your solar-powered system is configured, solar power is still a fantastic choice for alternative energy needs. For as long as the planet has existed, reliably and without fail, that hot yellow ball of gas has risen every morning on the horizon packing enough energy to meet our power needs consistently. The sun is a remarkable, free, silent and clean form of energy, and it’s just within the last 20 or so years that solar panels, inverters and batteries have evolved from an efficiency standpoint to the point where we can now create homes that are entirely powered by the sun.
While the solar panels themselves work identically in a grid-tied and off-grid system, the method of both storing the solar power and integrating that power into the home’s electrical system have some marked differences between the two, so much so that their paths diverge substantially. It’s not so much the panels themselves that we’ll be looking at; rather, it is what happens when the electricity leaves those panels and heads for your home that we’re examining.
GRID-TIE SYSTEMS
If you take a drive down your average suburban street and spot a home with solar panels on the roof, you can almost be certain the system is a grid-tied system, which is by far the most common solar-powered system in use today. As the name implies, the system is tied to the grid – what grid, you ask? The electrical power generation and distribution grid – essentially, all it means is that the home is connected to the power grid that feeds it, which isn’t earth-shattering until you understand the implications thereof. Here’s how it works:
- The home is already connected to the power grid regardless of solar panels. What most people don’t realize is that this connection is a two way street – power doesn’t just flow from the grid into the home; it can also flow from the home back into the grid.
- Solar panels on a grid tie-in system generate electricity when the sun is shining, and this electricity is routed to the home’s primary electrical distribution panel. If the home produces more electricity than it uses, the excess electricity is funneled back into the grid.
- If the home frequently produces more power via solar panels than it uses, the homeowner will realize a credit on his or her power bill representing a payment from the power company for the electricity that the home produced.
Harness the power of the sun when the power goes out…
Grid ties have one fatal flaw however; one Achilles heel that most people don’t know about: Your grid-tied solar panel system will not be able to power your home during a power failure. This is because the power company will put a lockout box on the output of the solar panels such that if the power is off, the box will disconnect the solar panels from the home’s electrical panel to prevent a back-feed situation. As we discussed earlier, electricity flows both ways, and the power company is concerned that the output of your home’s solar panel system could inadvertently shock a power worker halfway down the block who is working on the power lines and assumes they are inactive.
OFF-GRID SYSTEMS
Off-grid systems take solar panel technology to a new level. Essentially, they use the same solar panels as grid-tied systems, except they actually store the power they make, usually in batteries. This is an important distinction; the off-grid solar power user isn’t interested in generating power for some faraway utility; he or she is interested in keeping the power that is produced. The way the power is retained is by storing the output of the solar panels in an appropriately sized battery bank, and this provides another benefit most people don’t realize: You can use the solar power you generated during the day – at night. As the solar-powered system soaks in the sun’s rays during the day, it funnels this electricity into a purpose built battery bank which then can be drawn from at night or on overcast days, meaning that the off-grid system will be able to bank or save its output, whereas the grid-tied system will be running at a reduced capacity, or perhaps not at all.
PROS AND CONS
To sum it up, both systems have some plusses and minuses:
Grid Tie:
Pro:
- Initially less expensive to install on a home.
- Hundreds of thousands of examples of this system in use.
- Could result in a credit on your power bill.
Con:
- If there is a power failure, you have no electricity.
- Doesn’t generate solar power at night or on overcast days, so you’re back to using the grid.
Off Grid:
Pro:
- Stores solar energy in batteries for use at night and on overcast days.
- Independent power system not subject to the whims of the power utility.
- Works even if the power grid is down.
Con:
- Initial cost of the system is higher due to batteries and associated gear.
- Is not very common in a suburban setting – more common in remote homes.
Be sure to look into both systems, as each one has its own merits.