What You Need to Know Before Buying a New Hot Water Heater

Repairman Working on Water Heater

What You Need to Know Before Buying a New Hot Water Heater. A Phoenix Plumber Explains.

Despite our best hopes, water heaters don’t last forever and one day you will need to replace yours. A water heater installation is most quickly and easily accomplished by a professional plumber. The process will involve heavy lifting, cutting and soldering pipes and some minor electrical work so it is not a job for the average homeowner, no matter how handy you may be.

Before you can conduct a water heater installation you need to purchase one. The five main factors to consider in buying a new hot water heater are:

  • Fuel Source
  • Type of Water Storage
  • Function
  • Capacity
  • Energy Efficiency

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Most water heaters are fueled by gas or electricity. Most people will just purchase a water heater based on the system already in use in their house. If you want to explore your options, refer to the table below to compare the differences between the two.


  • Requires a slightly larger upfront investment
  • Must be vented outdoors for safety
  • Units with sealed combustion or power venting increase safety
  • Usually cost less to operate
  • Not affected by power outages (tank-style only)


  • Generally cost less than gas models
  • Easy to maintain
  • Requires no combustibles or venting
  • Heats water quickly
  • Offer high energy factor ratings

Water Storage

Conventional tank water heaters store water in an insulated tank until it is needed. Tankless units do not store water but heat it by running the water through coils. Each offers their own unique advantages, and you can compare features and benefits below.

Conventional Tank

  • Economical
  • Can be positioned in a closet, basement or garage
  • Capacity ranges from 20 to 80 gallons
  • Efficiency varies between models, brands and fuel sources


  • Require a larger upfront investment
  • Hang on wall and frees up floor space
  • Excellent option for residences occupied part-time
  • Reduce energy consumption by as much as 30%
  • Can run out of hot water during heavy usage
  • Requires ventilation

View our tankless water heater installation services

Whole House and Point of Use Systems

Conventional tank water heaters are whole house systems that send hot water from the tank through the house to the point where you want hot water. Tankless water heaters are typically whole house systems as well, but only heating water as needed. Whole house systems can provide hot water to more than one fixture at a time. Depending on the size of your home and the number of fixtures, you may need to consider adding additional hot water heating capacity.

Point of use systems are individual units that install directly under the sink or in a nearby closet. These systems deliver instant hot water to a specific place. Point of use systems will typically supplement a whole house system when instant or additional hot water is needed.


It’s important to buy a new hot water heater that provides enough hot water for your home. An undersized water heater will work harder and have a shorter lifespan.

Conventional Tank:

Determine the suitable capacity for your household based on your home’s FHR, or first hour rating. So the FHR is the measure of how much hot water the heater will deliver during a busy hour, such as first thing in the morning. You can determine your tank size needs using the following formula and a four-bedroom house as an example:

  1. Allot 12 gallons of hot water per person in the household.
  2. Figure the home’s maximum occupancy as the number of bedrooms plus one. In this case, we have four bedrooms, so we add one and get five. Now multiply this amount times the 12-gallon allotment and you end up with an FHR of 60. That’s the minimum FHR that this home should need on its water heater.
  3. When you go to buy your water heater, look for the FHR rating on the heater’s yellow EnergyGuide label.


To determine the size of the tankless hot water heater you need for your home, you’ll need to calculate how much hot water you’ll need at one time. This is called the flow rate and it is measured in gallons per minute (gpm). The table below provides average flow rates for typical household hot water applications.

    • Fixture/Appliance: Average Flow Rates
    • Bathroom Faucet: 0.5 – 1.5 gpm
    • Low Flow Kitchen Faucet: 3.0 – 7.0 gpm
    • Shower: 1.0 – 2.0 gpm
    • Dishwasher: 1.0 – 2.5 gpm
    • Clothes Washer: 1.5 – 3.0 gpm

To determine the gpm you need, add the gpms of the major fixtures or appliances you might often use simultaneously. For example, if you typically run the shower (2 gpm) and the dishwasher (2.5 gpm) at the same time, you’ll need to heat 4.5 gpm of water.

Energy Efficiency

No matter which fuel source you choose, a hot water heater can be the third largest energy user in your home, so you’ll want a unit that is as energy efficient as possible. Fortunately, almost all water heaters offer increased efficiencies to meet increasingly strict federal energy standards. Look for the Energy Factor (EF) rating on the unit. This rating measures how efficiently a unit converts energy into heat as well as how much heat is lost during storage. The higher the energy factor, the more energy efficient the water heater is. Look for EF ratings as close to one as possible. Electric heaters tend to have the highest EF ratings.

Need a Phoenix Plumber’s Expertise?

If all this is too daunting, your plumber should be able to help you determine what your hot water heater needs are. The technicians at Plumbing Masters can assist you in buying a new hot water heater for your home and your water heater installation. Give them a call today at (602) 296-1127 or schedule online today.

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