Can I convert a grid-tied inverter to work off-grid?

No. Grid-following and grid-forming are different hardware functions, not a setting. To get outage capability you either replace the inverter with a hybrid or add an AC-coupled battery system with its own grid-forming inverter alongside the existing one.

Why are off-grid inverters less efficient?

They do more work: creating a waveform from scratch, managing battery charge and discharge, and handling surge loads with no grid to lean on. They also run a constant idle draw to keep the AC output alive. Grid-tied inverters push current in phase with an existing waveform, which is electrically simpler and therefore more efficient.

Do I need anti-islanding on a genuinely off-grid system?

No, because there is no utility connection to protect — that is a large part of why off-grid permitting is so much lighter. The requirement appears the moment any part of the system touches the utility, which is why adding even one grid-connected circuit changes the regulatory picture completely.

Grid-Tied vs Off-Grid Inverters: What's the Real Difference?

They are not the same hardware with a setting changed. One synchronises to the grid and dies without it; the other creates its own AC and cannot legally export.

This looks like a configuration choice and it is not — the two types do fundamentally different electrical jobs. A grid-tied inverter follows an existing AC waveform. An off-grid inverter creates one. That single distinction explains every other difference between them.

Grid-following versus grid-forming

A grid-tied inverter senses the utility's voltage and frequency and pushes current in phase with it. It has no ability to establish an AC waveform on its own, which is why it produces nothing the instant the grid disappears — not as a safety cutoff bolted on afterwards, but because it has nothing to synchronise to.

An off-grid inverter is grid-forming: it generates the 120V 60Hz waveform itself, from the battery, with no external reference. That is a harder job and it is why off-grid inverters cost more per watt and always require a battery — there is nothing else to draw the instantaneous power from.

Side by side

	Grid-tied	Off-grid	Hybrid
Needs the grid to operate	Yes	No	No
Needs a battery	No	Yes	Yes
Can export to the grid	Yes	No	Yes
Works in an outage	No	Yes	Yes
Anti-islanding required	Yes	N/A	Yes
Cost per watt	Lowest	Higher	Highest
Typical efficiency	96-98%	90-95%	94-97%
Idle consumption	Negligible	20-50W	20-50W

Anti-islanding, and why it is not a flaw

Grid-tied inverters are required by code to shut down within milliseconds of losing the grid. The reason is that a utility crew must be able to treat a downed line as dead — an inverter still energising that line would create a lethal hazard, and it is the same reason backfeeding a generator through an outlet is illegal everywhere.

So the fact that your solar goes dark in a blackout is the system working correctly. Getting power during an outage means adding equipment that can safely disconnect from the utility first, not defeating the protection. Never attempt the latter.

Idle draw is the off-grid detail people miss

An off-grid inverter consumes 20-50W simply being switched on, because it is continuously generating a waveform whether anything is using it or not. Over a day that is 0.5-1.2 kWh — potentially a quarter of a small off-grid system's entire daily production, spent on nothing.

This is why oversizing an off-grid inverter is genuinely costly rather than merely wasteful, and why many off-grid systems use a search or standby mode that wakes the inverter only when a load appears. Check for that feature; on a small system it matters more than a couple of points of conversion efficiency.

Which one you need

Grid-tied — you have a reliable utility connection and want lower bills. Cheapest, simplest, and dark in an outage
Off-grid — no utility connection exists, or extending one is prohibitively expensive. Never the cheaper option when a grid connection is available
Hybrid — connected to the grid but you want the lights on when it fails, or your export rate is poor enough that self-consumption beats exporting

The system-level version of this decision, including costs and permitting, is in grid-tied versus off-grid versus hybrid. For the battery-backup specifics, see hybrid inverters explained.