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What Size Water Heater Should You Get?

Picking the right tank size for your hot water is critical to ensuring you get efficient and accessible water heating for the lifetime of your new unit.

The capacity needed for your new water heater is relative to each household: the number of people in your home, your lifestyle, your habits, the location of your home, and more have to be considered when making a sizing choice.


The easiest way to start, however, is to ask yourself if your current tank adequately meets the current demand of your household. If it does, then you can likely get the same size water heater and notice no difference. For cases where the tank does not meet demand, then sizing up will be the option. Going too big isn’t preferable either; the size can make installation and servicing cumbersome, energy losses build if the water is unused, and they require a higher initial investment.


Estimating delivery capacity

The main way to determine what size is right is by taking note of your household’s hot water use. By noting what appliances and faucets are in use at the time of the day when your hot water demand is at its highest, you’ll have a good benchmark for what your water heater needs to accommodate.


Below are a few general estimates for the hot water demand of various household appliances and activities.


Dishwasher 7-10
Laundry Machine 25-35
Shower 3/min (shampooing = 5)
Shaving 2
Cooking Prep 4-5
Bath 10-25
Dishwashing by hand 3
Hand washing 2

In a moment where your hot water use is at its peak, add the general demand for these activities together: maybe someone is showering while the dishwasher and laundry machine are running? Assuming this person takes an 8-minute shower and someone washes their hands at one point during the hour, our estimated peak demand is 58 gallons for a busy hour, keeping in mind the laundry machine doesn’t run every night. If the use of these appliances is better spread out during the day, you can get the peak use down drastically.


This peak use estimate you just calculated is measured directly against the tank’s first hour rating (FHR), a general measurement of how much hot water the tank can provide in a single hour from full. Using the FHR is a better way to choose your new water heater’s size instead of going by the tank capacity: it takes into account when the maximum amount of water is needed and matches it as opposed to constantly-heating an unnecessary amount for infrequent spikes in demand.


It is not uncommon for smaller-sized tank units to have higher FHR ratings than larger tanks given how much quicker they can heat incoming water. By sizing according to FHR, over the unit’s lifespan you’ll end up saving money in energy costs and save space in your home.


Additional factors in choosing size to consider

  • Household size
    • How many people reside in your home? How will this affect your peak use and subsequently, the necessary FHR for your new model?
  • Lifestyle and habits
    • Is there anything about your lifestyle that would influence how much hot water you use relative to average households? Do you and your family members take short showers? Do you and your family members do sports and thus might take multiple showers in a day and do more laundry? Do you cook elaborate meals and need to run the dishwasher often? All these factors and more are useful to consider in choosing the size of your new hot water heater.
  • Space
    • Importantly, the size of the water heater must match the available space you have in your home. Hot water heater tanks are large and cumbersome – ensuring that you have enough space to easily install and later access your water heater is important to servicing and maintenance. If space in your home is an issue, consider looking into [tankless hot water heaters] as a space and energy-conscious alternative.
  • Other miscellaneous factors
    • Other things to keep in mind are specific to your home and lifestyle: do you live in a remote location where having a large backup of hot water is beneficial in case of power outages? Is this water heater a point-of-use tank for a specific part of the house or a few select appliances?


Here at Pink Plumbing we work with our customers to determine the ideal hot water heater for your family and household. Feel free to call us to consult our technicians about the FHR of various models we offer, as well as the benefits of different sizes in regard to your needs.

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