Choosing the best water heater depends on your answers to a couple of key questions, but they aren’t hard to answer and should give you a good idea of the kind of water heating system you need.

The aim of any water heating system is to provide all the hot water your home needs and, more frequently nowadays, to do it as efficiently as possible.

For a traditional tank water heater this means re-heating water as infrequently as possible, using high-tech insulation to keep in heat, and an efficient heating mechanism to reduce waste. Unfortunately, no matter what improvements are made, tank based water heaters may never be as efficient as tankless water heaters.

But efficiency is only one part of the equation when choosing the best water heaters. Unlike a tank water heater which relies on holding a large reserve of hot water for use during peak times, tankless water heaters can produce a never-ending stream of hot water, but are limited by how large a stream they can heat at one time.

The best water heaters, in terms of efficiency, will provide for your needs with as little energy wasted in heating unused water as possible. So your aim when buying any tank or tankless water heater should be to establish your household’s hot water requirements throughout the day.

Calculating Your Hot Water Demand

What is your typical peak hot water consumption? Remembering to include any utilities like washing machines and dishwashers along with baths, showers, and sinks. Roughly how many hot water sources might be required at any one time?

How often do you need hot water? Do you only use hot water at a few peak times each day, or do you have a more frequent need? This will affect how energy efficient your change to a tankless water heater might be, as much of the inefficiency of tank water heaters is due to their constant heating of water, even when it’s not required for long periods of time.

Whatever your answers to the above questions, I have not seen a scenario where tankless water heaters do not come out on top in terms of efficiency and convenience, but choosing the best water heaters for your home does require more thought when buying a tankless system.

Tankless water heaters are generally rated by their ability to heat X amount of water to X temperature as it is used. Typically you’ll want your homes hot water at around 115° F, and require 1.5 GL (gallons) of throughput for each hot water source in use.