Water Heater Upgrade

[cruiser]

Thinking of adding an electric tankless hot water heater to my class b but would like some input from the forum members. The tankless heater requires a 20 amp circut breaker. My class b has a 30 amp power supply. My convertor box has a 30 amp main breaker and 4 -15 amp breakers. One of the 15 amp breakers has no wires attached thus not being used. My plan was to replace the unused 15 amp breaker with a 20 amp breaker dedicated to the new hot water heater.
The hot water heater only uses electicalal power when you are using the hot water. I will only be using the hot water for hand washing and dishes mainley. The other large power users are my air conditioner (8.5 amps) and the microwave. I am pretty sure I could not run the hot water heater, air conditioner and microwave at the same time without exceeding the 30 amps, but that is unlikey anyway.

Will this work?
Any other suggestions?

Thanks
Cruiser

[markopolo]

What do you use to for hot water now?
Is it a 6 gallon tank that uses propane? Does it need to be replaced?

You can get electric and propane combined models and you can add an electrical heating element to propane only models. I like reserve capacity in the traditional water heater. The water stays hot (or at least warm) for a long time. You might only need to heat up the water once a day.

[cruiser]

The unit did not contain a hot water heater installed by the factory. It did however contain a hot water device used to make instant coffee, oatmeal, etc. on the sink beside the faucet.

The tankless hot water heater would be an easy install under the sink and that is about all the room I have without making major modifications. These type heaters are typically used in concession stands, boats, etc.

Anybody tried this?
Will the 30 amp service handle this addition?

Thanks