WHAT IS A TANK WATER HEATER?
Choosing what water heating system to use in your house is a major decision – it can end up costing or saving you hundreds or even thousands of dollars per year. Each home has a slightly different requirement when it comes to water usage.
Generally, the key factors involved in choosing a tank water heater are:
What is your budget
Are you able to pay a higher upfront cost that you recoup in energy savings?
How much water will you use?
A family of five will use more hot water than someone living on their own.
What climate do you live in?
A cold climate will require more energy to heat water than a warm one.
How eco-friendly do you want to be?
There are many heating systems on the market that are more eco-friendly, although these tend to come with a higher price tag.
This guide will answer these questions. It addresses the different types of water heaters and how you can pick the best one for your home and family. For information on water heater costs, check out our guide on the average cost of a water heater.
HOW DO THEY WORK?
The majority of homes have tank water heaters, powered either by gas or electricity. Here’s how they work:
Fill the tank with water
They function by taking cold water into a tank and then using some form of heat to warm it to a pre-set temperature.
Heat the water
In a gas water tank, the water passes over a flame, which heats the water. In an electric tank, the water passes over an electrical heating element.
In both cases, a thermostat regulates the temperature, either continuing to heat the water or shutting off the heat when the water reaches the required temperature. Both types of tanks also contain a pressure relief valve to prevent heated water from building up too much pressure.
Pump water to point of need
When an appliance requires hot water (a faucet or a shower, for example), the water is pumped from the tank to the appliance.
Start over and refill the tank
The tank then takes in a new influx of cold water and begins heating it up.
There are slight variations in operations, efficiency, and cost across different types of tanks, but all operate using the same principles. Check out our page on average cost of a tank water heater for more pricing information.
TANK WATER HEATERS
According to the Department of Energy, between 14% and 18% of our utility bills are spent on heating water. The type of water heater you buy, therefore, has a major impact on your energy costs. There are four types of water heaters available: standard, high efficiency, solar, and point-of-use (tankless) water heaters. One of them – a point-of-use, or tankless water heater – is discussed in our guide, What is a Tankless Water Heater.
The remaining three all require a tank to store the heated water.
As the name suggests, this is the most common type of water heater. It uses either a gas flame or an electrical heating element to heat the water inside (for a comparison of gas and electric options, see the section below). Generally, the difference between the two is that gas tanks are more expensive to install but cheaper to run.
A standard tank water heater will generally have capacities of between 20 and 80 gallons and last between 8 and 15 years. They are also the cheapest of the four types of tanks listed here.
High-efficiency tanks are designed to be energy efficient – they are available in either gas or electric options. The key metric to use for gas water heaters is the Energy Factor (EF) rating. This is a rating given by the Department of Energy that determines how energy efficient a gas water heater is.
A standard gas water tank will have an EF rating of .50 or .60. By contrast, a high-efficiency tank heater has an EF rating of .67 or above. This means that they use 10% to 20% less energy than a .50 or .60 heater.
When looking at high-efficiency tanks, look for the Energy Star certification, which ensures that tanks have a high EF rating. For high-efficiency electric heaters, you can buy a heat pump heater. These draw heat from the surrounding air and use it to heat water – for this reason, they are not always suitable for cold climates.
Here’s some more info on heat pump systems:
Solar water tank heaters draw their energy from the sun. They require two main parts: First, a thermal collector – usually located on your roof or in your yard. Second, they require a backup tank to provide hot water on days when it is cloudy.
There are two different ways that solar systems can heat water. A direct system runs water through tubes in the collector, which are then heated by the sun. This water is run into a storage tank for later use. An indirect system (sometimes referred to as a closed system) heats an antifreeze fluid and uses this to heat the water inside your tank.
In many jurisdictions, there are grants or rebates for installing solar energy in your home. This can help mitigate the fact that although solar heating systems last for 20 years, it can about that amount of time to recoup the cost of installation.
POINT-OF-USE WATER HEATER
As the name suggests, point-of-use water heaters work with specific appliances in your home to provide hot water when needed. The most common type of installation is in a faucet. Installing a point-of-use heater in your faucet will save energy because you will only be heating the water you need.
Point-of-use water heaters come in smaller sizes than standard tanks – starting at 2.5 gallons. These are not currently Energy Star certified, but undoubtedly save you money on your energy usage by only heating small amounts of water as and when you need it.
See our page on the average cost of a tankless water heater to learn more about the costs involved with this type of water heater.
HOW TO CHOOSE A TANK WATER HEATER
Once you’ve decided what type of water heater to get, it’s time to choose a specific model. Again, this will be dependent on a variety of factors, related to your specific circumstances.
What are your family's needs?
The key question to ask is what your family’s needs are. A large family of five or six people will have different needs than a couple with no children. Similarly, where you live in the country will also play a role in shaping your requirements. A family living in Arizona or Hawaii will have different needs than a family in Michigan or Wisconsin.
There are two key metrics to consider when it comes to your family’s needs – the required capacity and the First-Hour Rating.
The amount of water you use will guide what size water tank you will need. To work this out, take a detailed record of your water usage over the course of a week. You can do this either by writing down your water usage each day (for example, how many times you run the laundry, how many times someone takes a shower). Alternatively, you can use your water meter to provide you with a guide.
Either way, you will get a sense of your water usage in gallons per week. This should be the primary determinant of your water tank’s size.
CALCULATING FIRST-HOUR RATING
First-Hour Rating (FHR) is a measure of how much hot water a tank can deliver within the first hour. If everyone in your home takes showers within a short period of time, for example, you will need a higher FHR than if your usage is more spaced out.
To give an example of what you need:
1 food prep
Total FHR Needed
47 gallons FHR
1 food prep
1 load of laundry
Total FHR Needed
99 gallons FHR
GAS VS. ELECTRIC
For more information on the difference between gas and electric water heaters, see our guide on Electric vs Gas Water Heaters.
Generally, however, the rule of thumb you can work off is that gas water heaters are cheaper to run than electric, but cost more to buy and install. Therefore, your decision should weigh up your budget against how long you intend to stay in your current home.
Electric heaters also tend to be easier to install and are safer (since there is no chance of a gas leak). You can also factor in your own DIY expertise in your decision-making.
Choosing the right water heater for your home is a crucial decision. If you choose the wrong option, you can end up paying higher energy bills or having a water tank that empties after the first person takes a shower.