Is this true?
Where does the extra power go when I turn appliances off when running from a inverter? ....no demand no output??
Appliances run on "voltage sources" (e.g., the grid, a battery, a capacitor, a non-GT inverter). That is they provide
current to try and keep the voltage constant.
So, when you switch on a blender, for example, the resistance drops from infinite and current rushes through the device. V=IR and the a voltage source wants to keep V constant so by knowing R you can calculate the current. Turn it off and the current stops as R increases to infinity.
Grid-tied inverters are "current sources". That is they try to push as much power as they can, raising the voltage to do so. This is how they push current uphill to the grid. So, a blender might have a fixed R when switched on, but a current source is only interested in pushing power, so it'll keep jacking up V to increase current to push everything available. The grid is big so pushing a few kilowatts uphill doesn't change the voltage much.
Take a look at the AC coupling release notes and you'll see most want you to have a battery sized to the number of panels, the way they work is they toggle the panels off until the batteries are discharged enough that sudden power shifts (e.g., Air Conditioning going off) can be funneled safely into the battery (or caps big enough to absorb it while they cut the relay to the panels).