Sizing a Tankless Water Heater: What You Need to Know
Choosing the right tankless water heater isn’t just about picking a model that “looks good and about right” – it’s about making sure it can keep up with your home’s needs without overdoing it. Sizing is crucial for an installation that provides all the hot water your household needs without overtaxing the heater. You may wonder, what size tankless water heater do I need? Let’s find out.
Household size
When choosing a tankless water heater, how many people are going to use it is one of the biggest factors to consider. More people means more showers, more laundry, and more dishwashing – so the unit needs to keep up with that demand. A single person living alone can get by with a smaller system, but a household of four or more will need a larger model to make sure no one ends up with a cold shower.
Simultaneous usage
When selecting the right tankless water heater size, think about how often multiple appliances run at once. If your household regularly has someone showering while the dishwasher or washing machine is running, you’ll need a bigger tankless water heater capacity to handle that much demand. The more simultaneous use, the higher the flow rate your unit should support. If you choose a model that’s too small, you could end up with barely warm water.
Flow Rate
Flow rate is another important thing to consider. It’s measured in gallons per minute (GPM) and tells you how much hot water the unit can deliver at once. Different appliances have different needs – most showers use about 2 to 2.5 GPM, dishwashers may need 2 to 4 GPM, etc. If multiple fixtures run at the same time, you’ll need to add up their flow rates to find the total GPM your system should handle.
Incoming Water
Incoming water temperature is another important factor. If the water is too cold, it takes more energy to heat, meaning the unit must work harder to reach your desired temperature. In areas with cold winters, this difference can be very noticeable – especially if the water enters the home at a much lower starting temperature. Warmer climates usually require less heating effort, so a smaller unit may be enough.
Fuel Type
Fuel type can affect both the size of tankless water heater and performance of a tankless water heater. Gas-powered models usually handle higher flow, so they’re more suitable for homes that use lots of appliances at once. Electric models are usually more compact and easier to install, but they may have lower flow capacities. Besides that, they require a lot of current. These heaters require a lot of electricity and don’t have high enough GPM, that’s why we don’t recommend installing them.
How to Size a Tankless Water Heater
Choosing the right tankless water heater sizing may be a bit more complicated than you’d think. There are a few important points to keep in mind to make sure you end up with a unit that keeps up with your needs. The right tankless water heater size will give you the right amount of hot water without overworking the system or wasting energy. If you’re not completely sure what’s best for your home, it’s worth getting professional sizing by a water heater company to make the best recommendation.
Calculate Peak Hot Water Demand
You’d want to know your peak hot water demand to understand the size of tankless water heater you need. This means adding up the flow rates (in gallons per minute, or GPM) of all appliances and fixtures you might use at the same time. This includes showers, sinks, dishwashers, and washing machines. Many fixtures have their GPM rating printed on them, but here are some general ranges: dishwashers 2-4 GPM, showerheads 1.2-2.5 GPM, clothes washers 3-5 GPM, and kitchen faucets 1.5-2 GPM. For example, running a shower, kitchen sink, and dishwasher together could total about 8.5 GPM. Choose a unit that can slightly exceed your total to make sure you have enough supply.
Determine the Required Temperature Rise
Knowing the required temperature rise is another thing you’d want to know. This is the difference between the incoming cold water temperature and the desired hot water output. For example, if your groundwater temperature is around 50F and you want 120F water, the system must deliver a 70F rise. Homes in colder regions may need higher temperature rises, while warmer climates require less.
Select a Tankless Water Heater with the Right Flow Rate
Once you know your calculated hot water demand and required temperature rise, choose a tankless water heater that can handle both. The unit should at least meet, if not exceed, your calculated flow rate while maintaining the required temperature increase. Getting a model with enough capacity is important if you want consistent performance during high-demand times.
Professional Tankless Water Heater Installation & Replacement in Franklin, TN
Choosing professional water heater tankless installation in Franklin, TN is important if you want a system that is set up for maximum performance and reliability. A skilled technician can handle electricity and gas tankless water heater sizing just right, handle all necessary plumbing and venting, and make sure it meets local codes. This means fewer issues down the road and better energy efficiency from day one.
Benefits include:
- Correct sizing for all your needs.
- Proper setup for safety and efficiency.
- Professional maintenance and care.
- You can be calm knowing the job is done right.
If your old unit is no longer keeping up, a tankless water heater replacement can be just what you need. Contact us today to schedule your installation and enjoy dependable hot water!
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FAQs
What Size Tankless Water Heater Do I Need for a Family of 2, 4, or 5?
A family of 2 typically needs a tankless water heater with a 6–8 GPM flow rate. For 4 people, 8–10 GPM is recommended, and a family of 5 may require 9–11 GPM. Actual needs vary based on appliance use and local temperature rise.
