How to Pick the Right Tankless Water Heater for You
by Joe Goldstein on Oct 30, 2018
Though tankless water heaters were once expensive appliances that couldn’t quite meet the demands of a large family, new technology has changed them. Leading plumbers agree that tankless water heaters have come a very long way in the last few years. Tankless water heaters today are dramatically more affordable, reliable, and efficient than they were just three or four years ago, which means a tankless heater could finally make sense for your home. That is, so long as you choose the right model for your home and family’s needs.
How do you know which tankless water heater is right for you? There are a few factors to consider.
If you’re replacing a water heater tank, you’ll likely have room for your tankless water heater without issue. One of the advantages of tankless water heaters is that they are much smaller than their tank counterparts. However, you still need to make sure that your tankless water heater is large enough to meet your demand.
The size you need depends on the flow rate you demand. Tankless water heaters can only produce so much hot water at any given minute, although they can keep producing that hot water every minute for as long as you have the taps on. Tankless water heaters are limited by flow rate, and the higher the flow rate of the faucet or appliance, the larger a tankless water heater you’ll need.
Flow rate is measured in gallons per minute or GPM. The Navien NPE-210S condensing tankless water heater has a maximum GPM of 10.1. That means it could supply hot water to two faucets at 2 GPM, a dishwasher at 3 GPM, and a washing machine at 3 GPM all at the same time. If you turned on your shower while all of these faucets and appliances were running, you’d be demanding more than 10 GPM and the Navien NPE-210S would no longer be able to meet demand.
Find Your GPM
Each tankless water heater has a different maximum GPM. To figure out what you’ll need, add up the GPM of every appliance and faucet you imagine you’ll run at once. Those who have low-flow faucets will be able to get away with less maximum GPM from their water heater because their fixtures demand less.
Tankless water heaters do cost more upfront than traditional water heaters so you may find that you need more maximum GPM than the tankless water heater at your price point. Installing low-flow faucets and showerheads can help you lower your total. You may also want to consider energy-efficient dishwashers and washing machines if you have older appliances, which use much more hot water than the latest models. As an added bonus, these new appliances might save you in utility costs!
Depending on your climate, water might enter your home at a high or low temperature. The lower the temperature your water starts at, the more powerful a tankless water heater you’ll need. Unlike a traditional water heater, a tankless water heater doesn’t heat water to a specified temperature. It only has so much time to heat the water, and only has so much power it can use, measured in British thermal units (BTUs).
According to the Department of Energy, you can assume your water starts at 50ºF (10ºC), but if you live in a very hot or cold climate, you may want to measure the temperature. You can also assume you’ll want your hottest water at 120ºF (49ºC). That means your tankless water heater has to raise your water temperature to 70ºF (39ºC). You’ll find that gas-powered tankless water heaters can accomplish this higher temperature rating, while electric can often achieve more moderate rises.
Once you’ve found a tankless water heater that can meet your BTU demand and can achieve the temperature rise you need, all that’s left to do is compare it to your budget. You know your budget best, but if you can’t find a tankless water heater that fits, call up your local plumber. They may be able to offer you cost-saving solutions.
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