Boiler vs Water Heater

Water heater fastened to wall

Many homeowners mistakenly assume both a boiler and water heater perform the same function. Since both home components heat and utilize water to perform their individual functions, it is often the main point that causes confusion among them. Before purchasing a new system, it's important to know the pros and cons of each heating appliance.

What is a Boiler?

Repairman working on boiler

A boiler is an appliance that heats water to convert it into steam to provide radiant heating, which is its primary function. The steam is distributed throughout the home through a circuit of pipes connected to radiators, radiant floor heating, etc. Rarely are boilers used to produce potable hot water.

What is a Water Heater?

A water heater is a home appliance whose primary function is to heat potable water for cooking, bathing, laundry, etc. There are two basic types of water heaters, those with a tanked storage system and those that are tankless.

Tanked Water Heaters

Tanked water heater controls

Tanked water heaters connect to your home’s cold water supply line. The water fills the tank where it is then heated to a preset temperature utilizing either electric heating elements or a natural gas burner.


  • Significantly cheaper than tankless systems
  • Cheaper to repair and maintain


  • Uses more energy resulting in higher power bills
  • Larger than their counterparts and require more space
  • Have a much shorter lifespan than a tankless system
  • Can run out of hot water when demand is high

Tankless Water Heaters

Tankless water heater fastened to wall

Tankless water heaters, also referred to as on-demand water heaters, do not have a holding tank. Tankless water heaters are also connected to your home’s cold water supply. The water is instantly heated when called for by turning on a hot water tap or activating an appliance that requires hot water.


  • Uses less energy as they heat water only when the faucet is on
  • Much smaller than a storage tank system
  • Last much longer than storage water heaters, with a lifespan that is typically 20 to 30 years


  • While a small system can adequately provide an endless amount of hot water to a particular faucet, they are incapable of supplying enough hot water to run several fixtures and/or appliances at the same time
  • Larger versions that are capable of supplying a whole house will cost much more than a tanked water heater
  • Professional installation is required for most installations without pro-level DIY skills
  • Most require natural gas or propane as a fuel source