Find the best tankless gas or electric water heater for your home. Get comparison reviews of instant, on demand water heaters to fit your needs..Although tankless water heaters are energy efficient, some people want the running cost to be even lower. For those persons, here is a heater from Rinnai which, by operating on natural gas, will further bring down their energy bills..The Rheem tankless water heater immediatly when installed. We opened it and discovered there was a clip missing from the factory for one of the lines..This water heater provides instant and continuous water for up to showers and faucets based on geographic location . Rheem Performance Tankless Electric Water Heaters help reduce energy usage, save on energy costs, and are small so they will be a perfect match for installations under a cabinet or sink in your home, office, boat or RV..