Most people who ask about going off grid do not actually want to. What they want is to stop buying so much electricity, or to keep the lights on in a power cut, or to store their solar for the evening.
Those are three different things and only one of them is genuinely off grid. Sorting out which you mean saves a lot of money.
The four things people mean
1. Storing solar for later The common case. You stay connected to the grid and add a battery so you use your own generation in the evening instead of exporting it. See solar batteries.
2. Buying electricity when it is cheap A battery charged overnight on a time-of-use tariff, running the house through the expensive evening peak. Works year round regardless of weather, and works with no panels at all. See a battery without solar and smart tariffs.
3. Keeping the lights on in a power cut Backup. This is a specific feature that has to be designed in and paid for, and a standard battery does not provide it. See solar in a power cut.
4. Genuinely disconnecting from the grid Rare, expensive and only really sensible where connecting would be more expensive still. See total off grid systems.
Which one do you want?
| You want | What you need |
|---|---|
| Lower bills, use more of your solar | Solar and a battery, grid connected |
| Lower bills, no suitable roof | A battery on its own, on a time-of-use tariff |
| Power during outages | A battery with backup capability and a changeover arrangement |
| Independence from the grid entirely | A large off grid system, and a realistic budget |
For almost everybody, the answer is one of the first three.
Why staying connected is usually right
Staying grid connected means:
- You can sell your surplus. See export payments
- You can buy cheaply overnight on a time-of-use tariff
- You do not need to size the system for the worst week of the year
- You do not need a generator for December
A grid connection is not a weakness in the system. It is the thing that lets you size the battery for a normal day rather than a fortnight of bad weather.