2 1/2 gal undersink heater - use hot or cold supply?

acidwater, have you looked into one of these puppies¿

Price of tea in China... hehe

Hot or Cold . I don't know if you'd get enough hot water using the cold supply or not but I'd try that first . If it didn't work I'd switch to the hot supply . Cutting the small faucet supply pipes above the shutoff valves , using flexible copper tubing & compression fittings it wouldn't take much to hook it up or switch supplys if necessary . You'd likely need reducers to connect the tubing to the inlet & outlet of the tank .

Phew! I'd rather boil up a pot o water on the stove and bring it into her than install that POS point of use electric tankless.
What part of 0.5 GPM don't you understand?

Heck, I make my missus carry in her own dang bucket o water n warm it up on the stove.

Southern Man helped me rig up one o them electric poiter use water heaters on my well hand pump...
It dint work worth a hillo beens.

I'd listen ta Redwood thats one smart fella.
He helped me git my new still runnin real good.