Constant duty solenoid

Can anyone recommend a constant duty 120v AC solenoid that can be activated using a 12V input? I am trying to only run my 120V AC water heater while vehicle is running so I do not drain the house batteries.
Thanks, yeah I was thinking a relay but where can I find a double pole 120V relay activated with a 12V input? The relay should be normally open so that when the alternator is NOT running, it does not connect to the inverter output.

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> 12Amp or less

Which is 110+ amps being sucked out of batteries.

I would not do that unless I was hooked up to shore power.

I doubt your alt is keeping up even while driving.

Consider going to direct fossil fuel HWS rather than electric
Ideally I can have it disconnect from shore power and connect to alternator (through the inverter) power only when alternator is running.
Any thoughts on just running another programmable inverter from the battery dedicated to the tank? Pkys suggested an 800w programmable inverter that I could set to only run when it see's over a certain voltage. I would still need a switch to select inverter or shore/gen.

After all of this I suppose I should also get a quote on having this connected to coolant lines for heating when the engine is running.

Ultimately I would like to connect this to a d4/5 but until then would like to have a solution that heats while driving.