Should You Use Your Batteries to go Off Grid?
If you’re thinking of getting solar and batteries for your home, then you may be excited by the prospect of cutting the cord to the mains electricity grid and never paying a power bill again.
But is that a realistic proposition?
In theory, you can go 100% off the grid with enough batteries, a good off-grid inverter and a generator to provide emergency power in extended periods of low sun.
However, there are five big problems with taking this off-grid route:
1) Your system will be at least three times more expensive than an on-grid battery because you need to buy:
a. Lots of batteries
b. Either a hybrid inverter or a battery inverter suitable for off-grid use. (Many hybrid inverters can supply backup power during a blackout but aren’t made for continuous use off-grid.)
c. Secure space that meets Australian fire safety standards for the batteries, inverter, and generator.
d. Lots of time from an off-grid expert to design the system so you won’t run out of electricity too often.
2) You can’t send any surplus solar you generate into the grid so you won’t receive a feed-in tariff. This means that even if your off-grid-capable battery system cost nothing, it would still make economic sense to stay grid-connected.
3) Unless you spend a massive amount of money, you will always have to be careful with how you operate your appliances so they won’t try to draw more power than your off-grid system can provide. If you live with other people, expect many arguments over who was responsible for either tripping the system or draining the battery.
4) Every so often, you will run out of electricity and have to run a generator, which can be noisy and expensive.
5) An off-grid system is not a case of install-and-forget. They need a lot of maintenance – especially generators.
So, having said that, why would anyone be crazy enough to plump for an off-grid system?
Here are four reasons you might choose to go off-grid:
1) There is no electricity grid where you live. Perhaps you live in the middle of the Simpson Desert or somewhere else equally remote.
2) The nearest grid connection is a long way from your home, and your local electricity network wants to charge you an arm and a leg to connect you. In this case, it may be cheaper to go off-grid – but be aware that even a small off-grid system will start at approx. $30,000.
3) You are connected to the grid but suffer frequent blackouts that cause you grief, and you want a system that can power your home through long-term grid outages. But even in this case, it will usually make sense to remain grid-connected to receive a feed-in tariff. Going entirely off-grid may only make sense for zero-export-limited homes that already can’t receive a feed-in tariff.
4) You’re crazy. Your house is already connected to the grid. Blackouts aren’t a problem, and you can get a feed-in tariff, but you just like the sound of going off-grid. You think it makes you more “independent” and protects you from the forthcoming apocalypse.
In fact, you’ve probably already got a big shed to put the batteries in. It’s the same one where you stored all the canned food in readiness for the Y2K bug / end of the world last time around – and you don’t mind spending at least $40k on an off-grid system that would only cost $13k if it was grid-connected or maintaining it.
Unless 1) or 2) or 3) above applies, it is economically and environmentally insane to insist on an off-grid solar power solution.
- Economically insane due to the cost being 3x higher.
- Environmentally insane because all your surplus clean solar energy will go to waste instead of being sent into the grid for others to use.
For that reason, the rest of this guide will assume that you are thinking of buying a grid connect (hybrid solar + storage) system for your home.