If your typical application is dish washing at a single sink, you will need larger quantities of hot water at a time than an instant water heater can easily supply. In this case a storage water heater is likely to be best. These pre-heat a quantity of water in a tank for later draw-off. Over-sink storage water heaters are the most economical and easiest to install. These are mounted over a sink and are supplied complete with a valve and a spout. However you are usually limited to locating them above a sink and you can also only serve one sink at a time.