On demand water heaters are an alternative to standard tank water heaters. However, they may not save on gas costs if the tank is located far away in the home, like in an attic. It takes longer to get hot water to distant parts of the home compared to a centrally located tank. One advantage is they are quieter than tank systems, but the increased gas usage from powering distant water may outweigh any savings. An app is suggested to further evaluate if switching is worthwhile.