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More or less (as I understand, I am not in the business), a typical GT inverter outputs current following the sine wave... I.e., when the AC sine wave is at 0 volts, it outputs zero amps. When the sine wave is at its peak voltage, it outputs 100% of available amps (sun+solar array).

There are other qualifications too... If the line voltage is too high or too low, or the line frequency is outside of ~60 Hz +/- 1 Hz, then the GT inverter shuts down. When the line voltage and frequency is within spec, the GT inverter waits 300 seconds (while still checking line voltage is OK), and when it times out, then it turns on its output again.

So for a "typical" GT inverter, if there is no 240 VAC and 60 Hz sine wave from the grid, it shuts down. A typical GT inverter has no capability of generating a 240 VAC @ 60 Hz wave form--So it cannot shock/electrocute a utility lineman, etc.

There are hybrid inverter systems too... This work in "GT Mode" when the power is good--And when AC main power fails, it disconnects from the AC mains (opens switch) and starts outputting 120/240 VAC @ 60 Hz to its output--Which is typically connected to a sub-panel. The power for the hybrid inverter, when AC mains have failed is provided by a local battery bank (which can have solar charging or even backup genset charging).

The modern Hybrid GT/OG inverter these days are very amazing devices--And pretty complex (and can be confusing to configure).

There are a few GT inverters which have a separate AC output that, when the AC mains fail, and you have full sun on the solar panels, can output 1,500 Watts or so of "emergency 120 VAC power". Of course, when the sun goes down, or there are cloudy skies, etc., these inverters cannot run the full 1,500 Watt output--So they can be of limited use (as always, depends on your needs). There is no backup battery, so during poor sun or at night, no output power.

There are lots of ways engineers and companies can supply "solutions" to emergency and backup power... It really depends on what you need and how much you want to spend. The issue with hybrid power systems is that they need large battery banks and batteries go bad after 3-15 years. So, there is always these added costs (replacement batteries, gt inverters that need repair/replacement every 10+ years, wasted energy recharging battery banks, etc.). A typical commercial computer installation will have a UPS (uninterruptible power supply) and battery bank for a short amount of power (15-30 minutes), and is intended only to carry the loads until a backup genset starts and is warmed up--For hours to days to weeks of backup power (depending on needs).

There are ways you can "mix" GT inverters with Off Grid AC inverters to work both when the AC mains are good, and when the AC mains have failed and the OG inverter is supplying energy to a "micro grid" setup (the "sub panel" in some cases)--And the GT inverters help keep the micro grid powered up, and also the OG inverter can take "extra power" from the GT inverters on the micro grid and even recharge the OG inverter's battery bank.

This stuff get complex quickly, and it is usually easier to describe/understand a system that addresses "your needs" (rather than a broad brush stroke of every possible configuration). A small cabin or village has different requirements vs those for a large hospital complex, etc....

-Bill