How to Size a Tankless Water Heater for Your Home or Office

Size might not matter with some of your other household items, but when it comes to plumbing appliances, it does. This size-theory is especially important for tankless water heaters. Tankless water heating systems are a great way to conserve water, reduce energy consumption, and lower monthly utility bills. But in order to reap the numerous benefits a tankless unit has to offer you must be sure that you select the proper size for your home or office.

Not to worry, sizing a tankless, on-demand water heater is easy, and we’ll tell you how to do that below!

Indianapolis Water Heater Installation and Repair
Water Heater Installation and Repair 317-784-1870

What is a Tankless Water Heater?

In terms of operation, a tankless water heater works very similar to your conventional make and model hot water heater, except that they do not store heated water in a tank, as they lack a tank entirely. Instead of storing heated water in a tank, they heat water when hot water is “demanded” by a person or appliance in the home. This is why they are also called “on-demand”, “demand-type”, or “instantaneous” water heaters. Not sure if a tankless water heater is a good fit for your water heating needs? See our blog, “Three Signs a Tankless Water Heater is Right For You” for help making your final decision. You can always contact a local Indianapolis water heater company for personalized answers to your questions.

Finding the Right Instantaneous Water Heater Size

When it comes to choosing the proper size instantaneous water heater for your home or office, there are two primary factors to consider: flow rate and temperature rise. Tankless water heaters are sized by this exact combination of factors. Next, learn what you need to know about flow rate and temperature rise in order to select the right size tankless water heater.

Flow Rate

The flow rate is how much hot water a water heater can generate. It is represented in in gallons per minute (gpm). If your tankless water heater does not have a flow rate that is high enough to meet your hot water usages, you will be restricted to using hot water on only one or two plumbing fixtures.

Average Flow Rates for Common Plumbing Fixtures:

💧 Bathroom Sink – 1 GPM
💧 Kitchen Sink – 1.5 GPM
💧 Bathtub – 4 GPM
💧 Shower – 2.5 GPM
💧 Dishwasher – 1.5 GPM
💧 Washing Machine – 2 GPM

With these average flow rates in mind, consider an example of how you might use your hot water on a daily basis. For instance, if you plan to run a load of laundry while taking a shower, you will need to have a tankless water heater with a flow rate of at least 4.5 GPM.

Temperature Rise

Flow rate comprehension is the first step, while understanding temperature rise is the next.  Groundwater enters your water lines at one temperature, but comes out of a water heater at a higher temperature; this is known as temperature rise. Temperature rise varies among states, as does climate, so you will need to pay close attention to your own region’s groundwater temperatures per season. In Indiana, the average temperature of groundwater is 54 degrees. Your hot water usage temperatures will likely range between 102 degrees (shower/faucets) and 120 degrees (dishwasher/washing machine). With this in mind, you will need a tankless water heater that manage this degree of temperature rise.

Who to Talk to for Trusted Water Heater Advice in Indianapolis, Indiana

Call Weilhammer Plumbing Co. Inc. at 317-784-1870 for free estimates, advice, and information regarding water heaters, anytime. Not only are we state-licensed master plumbers who specialize in water heater repair and service, we gladly provide recommendations and advice. Whether residential or commercial, we can provide all the water heater services you need. Call 317-784-1870 to get started.

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