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Proper Sizing for the Best Water Heater

tank-water-heaterHere’s a question consumers often ask when it comes to purchasing a new residential water heater: how large a system is necessary? People want to be sure they have a water heater that will regularly meet their daily requirements, but they don’t want to spend more than necessary on a water heater that’s too large and may end up wasting energy.

It’s a balancing act to find the ideal size water heater for your specific circumstances. The easiest way to do it is to let the professionals handle the job. You must have professionals to install the system—it’s way too large and complex a task for either amateurs or as DIY project—so it’s best to have them with you from the start to select the type of size of water heater that’s ideal for you.

Some of the basics of determining water heater size

We’ll show you a bit of what goes into the proper sizing for a water heater. Like sizing a heater or air conditioner for a home, sizing aims for a “sweet spot” of a system that’s large enough to meet demand, but not so large that it is inefficient. This is why no licensed plumber recommends a consumer impulse buy their own water heater and then call a professional to install it.

  • The first hour rating: For a tank or heat pump water heater, the first hour rating is the number of gallons of hot water the heater can supply per hour, if it starts with a full tank of hot water. This is the first rating professionals look at, since it combines a number of other factors such as tank capacity, the energy source (either gas burners or electric heating elements), and how much heating power it has.
  • Peak hour demand: This is the hour during the day when you use the most hot water, and how much hot water demand there is during this time. The professionals will work with you to make calculations based on how many people are in your house and what time of day the most hot water is used. For the majority of homes, peak hot water use is in the morning when people are showering. This number is used to determine the best first hour rating. So if your peak hour demand is 40 gallons, the best match for a water heater would have a first hour rating of 38 to 42 gallons.
  • Maximum temperature rise at given flow rate: If you are going to have tankless (“on-demand”) water heater installed, the calculations are different since these water heaters do not store water but heat it up as it’s needed. The professionals must determine the flow rate and the temperature rise necessary for the whole house. This requires determining the number of hot water appliances/taps that might be in use at one time, then adding up how many gallons per minute they use. This determines flow rate. Subtracting the incoming water temperature (the temperature of the water from the municipal supply) from desired output temperature determines the maximum temperature rise. Once the professionals know these numbers, they can accurately size a tankless water heater for a home.

This sounds complicated, but we’re professional with experience handling water heater installations. We offer excellent service for water heaters in Bethesda, MD and the surrounding areas.

Mallick Plumbing & Heating Is the Service Contractor of Choice in Maryland, Virginia, and the District of Columbia.

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