The Best Tankless Water Heater Buying Guide

Here are some tips and things to consider before purchasing your new tankless water heating system.

Make sure to choose the right size.

The first thing to consider is what size water heater you will need. Tankless water heaters vary in size. Some are small enough to take with you on a camping trip while others can be large enough to heat the water in large homes. So to make sure you purchase the right water heater for your home, you first need to think about what is the maximum hot water you will need to be using at once. Maybe your home has multiple showers that people will be using at the same time. Or maybe you live by yourself and will never be using hot water in more than one room at a time. Whatever your need may be there is a tankless water heater out there for you.

You have figured out how much hot water you need. Now what?

Flow Rate EstimatesBathroom Faucet:0.5–1.5gpm

Kitchen Faucet:1.0–2.0gpm

Low Flow Showerhead:1.0–2.5gpm

High Flow Showerhead:3.0–4.0gpm


Laundry Machine: 1.5–2.5gpm

Well you need to convert this into gallons per minute to find the right size water heater for you. Although water heaters that have lower flow rates are generally much cheaper, I wouldn’t recommend cutting any corners when it comes to choosing size. The water can go from hot to cold and will not stay at a constant temperature if the water heater is too small. On the chart above I have provided a general idea of the flow rate in gallons per minute that the average household appliances use. This should just be used as a guide; actual usage could vary for your house. Just add up the maximum gpm you will need at once and you’ll have the size of the tankless water heater you need for your home.

You mean temperature could affect my heater’s flow rate?

Yes, so you may want to consider the climate you are in before finalizing your purchase. Because the tankless water heater heats the water while it passes through the system, the temperature of the incoming water can have an effect on the flow rate that is coming out of your water heater. For instance if you live in a warm climate and the incoming water never gets below 70 degrees Fahrenheit then your tankless water heater will run much more efficiently because it only has to raise the temperature of the water slightly which could even increase your system’s flow rate. The bad news is that this means for those in colder climates, your heaters will be less efficient because your water temperature will need to be raised much higher and could lessen your flow rate. This may not have a drastic impact on the efficiency but it is something to consider when making your purchase. Just remember that the colder your climate is, the less flow rate your tankless water heater will produce.

Consider if you need Gas or Electric.

When choosing between gas or electric there are a few things to think about. Gas powered tankless water heaters will require ventilation so unless you already have an easy way to make a vent for your new tankless system, I would recommend going with electric. Electric water heaters do not need ventilation so it gives you more options where to install the water heater. Also electric water heaters are cheaper to purchase but have a slightly higher cost to operate on average. Whichever route you choose to go keep in mind when installing to make sure you have the correct voltage or gas line to fit your water heater. Also you may want to note if you are planning on saving hundreds of dollars and installing the system yourself that you could possibly forfeit certain warranties which include lifetime warranties for many products by not having a licensed professional install the system.

Full guide:

One clap, two clap, three clap, forty?

By clapping more or less, you can signal to us which stories really stand out.