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Tips from the Pros: What Size Water Heater Do I Need?


Buying a new water heater does not have to be difficult.

Adeedo!’s Southern California plumbers are here to make the process less frustrating and to give you confidence that you have made the right purchase.

So, when you are looking into what size water heater you need, you will want to take the following into consideration. First, determine whether you will be using a gas or electric hot water heater.

Next, you will need to figure out if you will be using a traditional storage tank water heater or a tankless heater.

Traditional Or Tankless?


Traditional storage tank water heaters are the most common water heaters. Most homes have either a 40- or 50-gallon water heater. Or you may choose to go smaller depending on whether you are the sole resident or larger if you more than five people on the property or serious hot water demands.

Generally, our San Bernardino, Los Angeles and Orange County plumbers recommend the following sizes:

Number of People Gallons
2 or fewer 23-36
2-4 36-46
3-5 46-56
5 or more 56+


Tankless water heaters, also called demand water heaters, provide hot water as it is needed. They are more economical and save more energy than traditional storage heaters. The process for determining the right tankless water heater is a bit different though.

First you will need to identify your flow rate. Your flow rate is the gallons per minute of hot water you expect to use. The chart below will help you determine this figure.

Fixture/Appliance Typical Flow Rate
Bathroom Faucet 0.5-1.5 (GPM)
Low-Flow Kitchen Faucet 1-2.5 (GPM)
Shower 1-2 (GPM)
Dishwasher 1-2.5 (GPM)
Clothes Washer 1.5-3 (GPM)

When determining this number you will want to consider whether you foresee yourself using more than one appliance at a time. For example, if you plan to use a bathroom faucet with a flow rate of 1.0 and the shower (with a flow rate of 1.5) at the same time, your expected flow rate would be roughly 2.5. Therefore, you will need a unit that can handle a flow of at least 2.5 GPM (gallons per minute).

Once you’ve established your GPM needs, you will then want to look at the average ground water temperature for your area. You can use the map here to help determine this figure.

Now that you’ve discovered both your flow rate and ground water temperature, you can use this info to select the right tankless unit. All tankless units list their maximum GPM at different ground water temperatures making it easy for you to select the right model.

Still unsure what type or size water heater is right for you?

No worries! Our highly skilled plumbers, serving San Bernardino, Los Angeles and Orange County, here at Adeedo! can help. We can figure out which unit will best suit your needs and actually complete the installation for you. For more information, to make an appointment or receive a free quote, give us a call at (833) 936-1791.

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