In some respects, the concept of going off-grid couldn't be easier to grasp.
On-grid solar systems are connected to the grid. Off-grid systems aren't. It doesn't get much simpler than that.
But, like most easy answers, this one doesn't really tell you anything you might want to know.
How does going off-grid affect your access to power? How does it affect the equipment you'll need?
If you choose to stay connected, what happens to your solar system during a blackout?
Today we'll take a look at these and other important practical differences anyone considering an off-grid solar system needs to be aware of.
On-grid solar systems
In the industry, "grid-tied" is the technical term for solar systems that remain connected.
The vast majority of homeowners who go solar choose a grid-tied system. And for good reason. Remaining connected to the grid gets you:
A reliable power source at night and at other times when there isn't enough sun to generate an appreciable amount of solar energy
A way to sell the surplus solar power your system generates on sunny days back to your utility company
In states like Pennsylvania—where utilities are required to compensate you at the very same rate they charge—this effectively lets you "bank" the surplus solar energy you get during peak-sun hours for use at other times when there's not enough sun to meet all your energy needs.
Remaining connected also allows homeowners who lack sufficient roof space to generate all the solar energy they need to still reap the financial benefits of going solar.
Suppose, for example, you need 1000 kWh of electricity every month to power your home, but the largest system that fits your roof will only generate 900 kWh. If you stay connected to the grid, you can save money on 90% of the electricity you use by going solar while continuing to pay your utility company's higher rate for only the remaining 10%.
Off-grid solar systems
When you choose to disconnect from the grid, on the other hand, your solar system has to be completely self-sufficient.
That imposes a number of strict criteria. In general:
Off-grid solar systems have to provide all the power you need down to the last kWh
Since the sun will be your only source of power, your power consumption will be completely limited to the amount of solar energy your system produces.
That means, if you don't have enough space for a solar system that meets all your current energy needs but are, nonetheless, determined to go off-grid, you've only got two options:
Make up the deficit by buying gas or propane each month and burning it in a generator (which sort of defeats some of the purpose of going off-grid).
Start using less energy.
A battery for storage
Off-grid solar systems also generally need to include a very large solar battery to store any surplus energy they produce.
After all, even if you've got enough roof space to generate all the solar power you need off-grid, it's only going to be generated when the sun is shining.
That means no power at night, no power in the evening, and no power in the early morning... unless that is, you've got a battery to keep the surplus solar energy your system produces mid-day in reserve,
Power outages
Going off-grid does, however, have one advantage.
Though many people assume that their solar panels will continue to provide power during a power outage, for safety reasons, grid-tied solar systems are designed to shut down completely during power blackouts.
Remaining connected to the grid means that your solar system is a part of it.
And generating power at one portion of the grid while technicians are working to fix the rest of it would be hazardous to them and everyone else involved.