Grid-Tied vs Off-Grid Calculator
Compare a grid-tied and an off-grid solar system on cost, storage requirement and what happens during a power cut.
Results
The honest comparison
A grid-tied system has no batteries: surplus goes to the grid, shortfall comes back from it. It is the cheaper build by a wide margin and usually the faster payback. The catch is that a standard grid-tied inverter shuts down in a power cut, for the safety of anyone working on the lines.
An off-grid system carries its own storage. The battery bank is normally the largest single cost, it wears out sooner than the panels, and it has to be sized for the worst week of the year rather than the average one.
Where the middle ground sits
Hybrid systems keep the grid connection and add a smaller battery for essential circuits. That covers outages without paying for a bank sized to run the whole house through a dark December.
Common mistakes
Going off-grid to save money on a property that already has a grid connection. Once storage is included, the lifetime cost is almost always higher. Off-grid earns its keep where a connection is expensive, unreliable or physically absent.
Questions people ask
Will grid-tied solar work in a blackout? Not on its own. Anti-islanding protection disconnects the inverter so it cannot backfeed the network. A hybrid inverter with a battery and a changeover arrangement is what keeps the lights on.
How many days of autonomy? Two is a common compromise; three or more is the honest figure for a winter with no generator.