Your hot water heater is one of the most important systems in your home, but many homeowners do not think much about it until it needs to be replaced. When that time comes, one of the biggest decisions you will need to make is choosing the right size water heater.
Selecting the correct size is important. A unit that is too small may leave your household running out of hot water, while an oversized system may waste energy and increase utility costs.
Three Key Factors When Choosing a Water Heater
No matter what type of system you choose — tankless, storage tank, electric, or gas — there are three important things to consider:
- Household size – The number of people living in your home.
- Peak water demand – The amount of hot water used at the same time during your busiest period of the day.
- Available space – The physical space you have available for installing the water heater.
For example, if several showers are used every morning, your system needs enough capacity to keep everyone comfortable without running out of hot water.
Tankless Hot Water Heaters
Tankless water heaters provide hot water on demand instead of storing heated water in a tank. Because of this design, sizing is based on performance rather than tank capacity.
Flow Rate
Flow rate measures the maximum amount of hot water the system can produce at one time. It is typically measured in gallons per minute (GPM) or litres per minute (LPM).
If only one shower or fixture is used at a time, you will need a lower flow rate. However, if multiple showers, taps, and appliances may run simultaneously, the system will need a higher flow rate.
To estimate the required flow rate, add together the flow rates of the fixtures that may be used at the same time, such as:
- Showers
- Sinks and faucets
- Dishwashers
- Washing machines
Temperature Rise
Another important factor for tankless systems is temperature rise. This is calculated by subtracting the incoming water temperature from the desired hot water temperature.
Desired Hot Water Temperature – Incoming Water Temperature = Temperature Rise
In many parts of Canada, incoming water temperature is often estimated around 10°C unless you have more precise measurements.
Storage Tank Water Heaters
Storage tank water heaters are the most common type installed in homes. These systems heat and store a fixed amount of hot water inside the tank until it is needed.
When choosing a storage tank system, several additional factors should be considered.
First Hour Rating (FHR)
The First Hour Rating measures how much hot water the tank can deliver during one hour of heavy use. This includes both stored hot water and the water reheated during that hour.
For example, if a system has a First Hour Rating of 90 gallons, it can supply approximately 90 gallons of hot water during a one-hour period.
You generally want a First Hour Rating that exceeds your home’s peak water demand.
Recovery Rate
The recovery rate measures how quickly the tank can heat new water after the tank has been drained. A higher recovery rate means the system can refill with hot water more quickly.
Fuel Source
Whether the system uses gas or electricity can affect both performance and tank size. Gas systems often recover faster, while electric systems may require larger tanks to deliver similar performance.
Bathtubs and Large Fixtures
If your home has a large soaking tub or spa-style bathtub, it is important to choose a system with enough capacity to fill it properly. Otherwise, you may end up with lukewarm baths.
Choosing the Right Size Matters
If a water heater is too small, you will quickly run out of hot water when multiple fixtures are used. If it is too large, the system may waste energy and increase your monthly utility costs.
Before making a final decision, it is always a good idea to consult with a professional who can evaluate your home’s needs and recommend the right system.
If you are considering replacing your water heater, The Gentlemen Pros can help with professional plumbing services and expert installation to ensure your home has the hot water capacity it needs.