Is My Water Heater the Right Size?

Choosing the right size water heater is important for any Indianapolis household. If your water heater isn’t large enough for your family, there’s not enough hot water to go around; if your water heater is too big, you waste money heating hot water you don’t need.

If you don’t currently have the right size water heater, replacement solves the issues that come with under- or over-sizing. Mr. Plumber’s licensed plumbing processionals help you find the right size water heater through careful assessment of your home and consideration of your household. For water heater replacement, contact us today!

What If I Don’t Have the Right Size Water Heater?

Water heaters come in all different sizes. However, it’s important that you have the right size water heater – sizing is determined based on your household’s needs. When you have a water heater that is too small or too large for your household, some significant issues arise.

Undersized Water Heater

If your tank water heater is too small for your household, there simply isn’t enough hot water to go around. The water heater may have been undersized from installation, or your household’s hot water demand may have increased, and your water heater is now unable to keep up. Remodeling and/or installation of new fixtures and appliances increase consumption and the number of hot water applications in use simultaneously.

When a tankless water heater is sized too small, you don’t run out of hot water as you do with a tank unit. Instead, water flow rate through taps is negatively impacted. The temperature of water remains consistently warm, but its flow from fixtures diminishes. Diminished water flow causes great discomfort and difficulty using hot water when you need it.

Oversized Water Heater

When your tank water heater is too big for your home, you have ample hot water, but issues occur in other areas. An oversized water heater heats more hot water than your household needs, which wastes energy. With a tank water heater that stores hot water for use, energy is also wasted storing more hot water than is used at any given time. 

Oversized water heaters consume more energy than properly sized models, so your utility costs are noticeably higher. Plus, bigger models are more expensive upfront, so you’ve also wasted money on the initial equipment purchase. The same goes for tankless water heaters that are too big – they waste energy and money.

How Are Water Heaters Sized?

Water heater sizing is different for tank and tankless water heaters. Storage tank water heaters are sized based on first hour rating (FHR), which is the number of gallons of hot water it is able to produce each hour. Tankless water heaters are sized based on the number of gallons per minute (GPM) the unit is able to produce at the correct temperature rise.

In both styles of gas water heaters, BTU (British Thermal Unit) rating is also important. A water heater’s BTU rating shows how much energy the unit requires to heat one pound of water by one degree. The appropriate BTU rating for the right size water heater in your home depends on preferred hot water temperatures and incoming water temperatures. Typically, residential gas water heaters have a BTU rating of 30,000 to 40,000 BTUs per hour.

In Indiana, you must consider that incoming water enters the water heater at various temperatures throughout the year. During summer months, water comes into the system warmer than it does in winter. Select a new water heater with a BTU rating sufficient for wintertime water heating to ensure year-round hot water. 

Sizing Tank Water Heaters

In order to find the right size water heater, a plumber determines your household’s peak hour demand. The peak hour demand is the amount of hot water that is consumed in the peak hour of use, measured in gallons per hour (gph).

To determine a household’s peak hour demand, plumbers consider the following factors:

 

  • How many people are living in the house? Homes with one or two occupants typically require smaller capacity water heaters than large families.
  • What hot water-consuming activities occur in the house? These include showers, baths, running the washing machine, using the dishwasher, washing by hand, etc.
  • When do occupants prefer to do these activities? Do some shower in the morning and others at night, or is there a rush to catch a shower at a specific time before the hot water supply runs out?
  • Do these activities take place simultaneously? Are occupants showering across different bathrooms at the same time, are washing machines running when dishwashers are?
  • How do occupants prefer to perform these activities? Are long, hot showers common or are showers short with cooler water? Are tubs filled to the brim for baths or is a shallow water level used?
  • What type of fixtures are in the home? Fixtures like jacuzzi tubs and spa showers require more hot water volume to deliver the experience users desire.

 

With all these factors in mind, plumbers estimate the average volume of hot water used for all activities taking place in the peak hour. A total of these estimates shows the household’s peak hour demand.

The right size water heater will have a first hour rating (FHR) that is slightly lower than your household’s peak hour demand. This ensures your new tank water heater has the capacity to supply all your home’s applications with ample hot water when needed.

You’ve probably heard of tank water heater capacity measured in gallons. Many homeowners mistakenly believe this refers to the volume of hot water the tank holds, but it actually represents the water heater’s first hour rating – the volume of hot water it produces per hour.

Sizing Tankless Water Heaters

Tankless water heaters are also known as on-demand water heaters, because they heat water as it is needed in the home. Sizing these units is different than sizing a tank water heater because a tankless model functions differently. 

To find the right size water heater for tankless models, the most important factors to keep in mind are flow rate and temperature rise. 

    • Flow rate refers to the volume of water moving through a fixture when in use, in gallons per minute. 

 

  • Temperature rise is the temperature of incoming water subtracted from the desired output temperature. 

 

As a plumber works to size a tankless water heater, the flow rates of all fixtures you want to be able to use at the same time are added up, which gives the needed flow rate from the new tankless water heater. Safety and household preferences are reviewed to determine the desired output water temperature, and incoming water temperature is measured to find the necessary temperature rise a new unit needs to provide.

Once these figures are found, your plumber is able to recommend the right size water heater capacity for a new tankless unit. It’s smart to round up slightly to help ensure the new model is able to meet household demands.

Sizing Estimates for Water Heater Replacement

When it’s time to replace or upgrade your existing unit, it’s always best to work with a licensed plumber in order to find the right fit for your household. While the right size water heater varies from one household to the next, general estimates provide a starting point for homeowners to begin their search.

The sizing estimates below are rough recommendations for the right size water heater, based on household size, fixture usage, and other factors.

Tank Water Heater Sizing Estimates

The following estimates give you a rough idea of the capacity you need to look for when you purchase a new tank water heater:

  • For households of 1 to 2 people: 30-gallon water heater
  • For households of 2 to 3 people: 40-gallon water heater
  • For households of 3 to 4 people: 50-gallon electric water heater/ 40-gallon natural gas or liquid propane water heater
  • For households of 5 or more people: 80-gallon electric water heater / 50-gallon natural gas or liquid propane water heater

Tankless Water Heater Sizing Estimates

If you wish to purchase a new tankless water heater for your home, these sizing estimates show you where to begin your search.

  • If you plan to use 1 to 2 fixtures at the same time: minimum flow rate of 3.5 GPM
  • If you plan to use 2 to 3 fixtures at the same time: minimum flow rate of 5 GPM
  • If you plan to use 3 to 4 fixtures at the same time: minimum flow rate of 7 GPM
  • If you plan to use 5 or more fixtures at the same time: consider a sequence of more than one tankless unit

Find the Right Size Water Heater with Mr. Plumber

Don’t make the mistake of buying an undersized or oversized water heater for your Indianapolis home! Mr. Plumber’s licensed plumbers assess your household’s hot water demands in order to determine the right size water heater to keep everyone happy. The right size water heater ensures everyone has ample hot water whenever and wherever needed!

For new tank and tankless water heater installation, call Mr. Plumber today to receive an estimate. We offer a range of quality equipment in both system types, installed by skilled professionals who ensure the performance and efficiency of your new water heater.