Hooking up high efficiency dishwasher up to cold water versus hot
 

Last year I got one of those high efficiency low water using dish washers.
I hooked it up to hot as per the instructions.
Ran it for a while with the hot water heater off/broken. Seemed to work fine with the dogs precleaning all the plates and bowls.
Then I put the tankless hot water heater on the hot water line. Problem with the tank less is when the dish washer fills the tank less heater doesn't kick on right away.
So all it does is warm the water in the line.

I'm thinking just connect it to cold water.
Now with it wasting hot water it's still not getting hardly any warm water at all. So might as well run it cold.

Might as well. I run mine on the cold line. One thing you'll notice is the initial rinses don't work as well. But by the time you get through the hot wash the plates et al are fine for the final rinse.

Dishes still come real clean.

Ps- using a dishwasher on off grid solar. :)

Lithium rules

If they come out clean, they're clean.

If you have really long hot water lines you might actually be wasting energy if its hooked up to the hot line, you'll just be heating the water line while the water going into washer will just be cold, just like you described.

Tankless system should be turning on almost as soon as there is demand; might be worth it to shutoff the hot water to hand-washing taps to prevent excessive cycling. There might be a setting where you can adjust this, I've never owned one.

You might also consider turning on the hot only when you are going to take a shower, and keeping it off all other times. You can get similar performance to tankless with regular tanked systems, if you heat it judiciously like this on a timer or just manually on-off, you do want to use small capacity tanks if you are doing this tho.

I think using air dry vs heated dry is where you save a ton of energy on dishwashers.