If it`s the same over engineered, maintenance hungry, always something going wrong, pieces of **** like the residential units which I refuse to install then I`d pass.

The upside is the whole basement/house smells like carnival fries after a backflush... mmmmm.... carnival fries. Lol

I know the tankless water heaters work great on gas or a high voltage. What I was trying to find out was can a 115volt 1800 watt .04 gpm unit used during summer months heat water enough to make it useable?

Usable for what? Rinsing off, like a transom shower? Maybe.
Using it for an actual shower? No.
A normal shower rolls 105-120* at 1.5gpm(low-flow) to 2.5gpm(average).
At .4gpm (and roughly 95*), it's going to be about like a dog pi$$ing on your leg.

Those small POU units are designed for tepid water from low flow sink faucets.

Check the specs out on this one:
https://www.titanheater.com/proddeta...?prod=SCR2-N10

But if you're on 30a shore service, you're going to be showering by candlelight. 26* rise at 1gpm and 18* rise at 1.5gpm, though. Tolerable.

Ended up going with Chronomite SR-15 120 has a 31 degree temp rise and only pulls 15 amps only need the water to be comfortable. Will see how it works.

Gas ones work well, electric, not so much. My electric draws 36,000 watts, thats 3x50amp at 240V to get a good hot decent shower. Go gas..

Get an old blow up mattress .put it on youre t-top or bow ,fill with water insall small drainage hose and ,go out on a sunny day. Wallah = hot rinse water

Spray self down w Simple Green- Jump in Lake- Clean! Wife mayNot appreciate tho lol