Remember to flush your water heater to remove sediment build up from the bottom. Standard gas water heaters heat from the bottom and if there is a sediment build up it really cuts down the efficiency of the heater. Tank-less water heaters should be flush out yearly for warranty and performance. There's several screens on some models that can get clogged or partially clogged reducing performance. They also have sensors that can be effected by a build up from hard water.