Home AppliancesWater Heater

How an Electric Hot Water Heater Works

Close-Up Of Hands Setting The Temperature Of Water In Electric Boiler In The Shower Room

Water heaters are a core part of modern comfort and convenience. In the past, many water heaters used gas; however, electrical water heaters are becoming more popular.

These have no open flame or obvious heat source to the untrained eye, and a layperson might wonder how they work.


There are three key phases in an electric water heater:

  1. The cold water is pumped into the tank.
  2. The bottom heating element warms the water.
  3. The hot water rises to the top of the tank, which is kept warm by a second heating element.

Keep reading for a more detailed explanation of electrical water heaters and a handy diagram.

6 Parts of Electric Water Heaters (and How They Work)

An electric water heater has a handful of parts that the water will travel through in succession. Let’s go over what they are and what they do.

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A basic diagram of an electric water heater.

1. Cold Water Pipe

Connection Of Water Supply, Hot And Cold Water To The Boiler

The cold water pipe is where the water is sent into the tank. This water is not heated and comes straight from the utility grid.

2. Dip Tube

The dip tube is a long tube attached to the cold water pipe, which takes the cold water to the bottom of the tank. This prevents the cold water from mixing with the hot water near the top of the tank.

3. Tank

Wall Hung Gas Boiler And Electric Water Heater In Boiler Room

The tank is the main body of the water heater and stores the water. It also contains the heating elements and the thermostats.

4. Heating Elements

Master Installs A New Electric Heating Ten In A Water Tank

Instead of a burner (like those found in gas water heaters), electric water heaters have heating elements.

There are usually two – one near the top of the tank and one near the bottom. They are made of heat-resistant metal rods.

Electricity is pumped through the metal rods, similar to the filament in a lightbulb. This causes the rods to become very hot. This heat then transfers to the water.

5. Thermostats

Female Hand Turning On Electric Water Heater

The temperature of the heating element is controlled with thermostats. Most often, there is one thermostat for each heating element.

The thermostat controls how much electricity is pumped into the heating element and, thus, how hot it gets.

6. Hot Water Pipe

Copper Valves And Pipes On A White Wall

Once the hot water is needed, it is pulled out of the tank via a pipe near the top. This pipe only pulls hot water because heat rises, meaning the hottest water will always be near the top of the tank.

Why Isn’t My Water Heater Working?

A broken water heater is a common problem as parts wear out. There are two common causes:

1. Bad Heating Element(s)

Heating Element Rust And Scale On Boiler

The most common part of wearing out is the heating element. The heating elements are repeatedly heated and cooled, which puts a lot of stress on the metal and will eventually cause the rod to wear out.

This is the first thing I check if a water heater is producing lukewarm or cold water. Luckily, these parts are designed to be replaced and easily switched out.

2. Bad Thermostat

Repairman For An Electric Boiler Connects The Wires To A Thermostat

You could also have a problem with the thermostat regulating the electricity to the heating element, but this is much less common.

Such a problem usually occurs because the wiring in the control panel or the computer chip has corroded.

The thermostat can also be popped out and replaced, although this is usually a trickier fix.


An electric water heater works similarly to a gas model. However, electric models rely on metal rods heated with electricity instead of a burner near the bottom of the tank.

This is a very efficient way to create heat, but it will eventually wear out the heating element. As such, the heating element is the most common problem when an electric water heater isn’t working.

Frequently Asked Questions

How Does a Tankless Water Heater Work?

These models are usually also electric but lack a water storage tank. They are designed with much more powerful heating elements inside the water pipes.

This means the water is heated during its journey to your tap in seconds. The result is an endless hot water supply, so you’ll often see these units referred to as “forever water heaters.”

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