WATER HEATER Sizes: How to choose?

Many times when someone finds out what size water heater they have they think about upsizing or downsizing their water heater. If you are thinking about downsizing your water heater, keep in mind that this is not always possible. Plumbing code requires that you keep at least a minimum first hour rating on the water heater that is in your home. The minimum rating on your water heater is determined by the number of bathrooms and bedrooms in your home. You can reference the chart below to see what the minimum for your home.

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Sizes of water Heaters


This size is the smallest size water heater that is not designed to be a point of use water heater for a single fixture. A 30 gallon water heater should be able to supply enough hot water to meet the needs of a household of 1 -2 people with only one bathroom. A good way of measuring your hot water requirements is calculate your peak hot water usage and compare it the first hour rating of a water heater. To calculate your peak hot water usage, fill out the peak usage worksheet found here. The first hour rating is a measurement of how much hot water you can get out of your water heater in its first hour of operation (starting with a full tank of hot water). The first hour rating on 30 gallon tanks is between 42 and 53 gallons so they are limited to one bedroom and one bathroom applications.

40 Gallon water heater

A very common size, the 40 gallon water heater works well for 2 – 4 people. These tanks are often found in homes that have 1.5 bathrooms. If you are running out of hot water with a 40 gallon tank, it is often possible to upgrade to a 50 gallon tank without much modification. It typically requires a couple of extra inches of available width for the tank. Upgrading to a 50 gallon would likely provide about 15 gallons of additional hot water during your peak hour of usage during the day. This can go a long way towards ensuring you don’t run out of hot water. Electric 40 gallon water heaters typically have a first hour rating of 40-57 gallons. Gas 40 gallon water heaters on the other hand are in the 67-73 gallon range for their first hour rating.

50 gallon water heater

A 50 gallon water heater is the most common tank we install. It is such a common size because it can supply hot water for 3 – 5 people. Considering an average shower uses 17.2 gallons of water you can typically have enough hot water for up to five people to take a shower within an hour. The first hour rating on 50 gallon water heaters range from 60 gallons with an electric water heater to 95 on a high end gas water heater.

75 Gallon water heater

We only see this size of water heater tanks currently for gas water heaters. 75 gallon water heaters are able to provide a whopping 120 gallons of hot water in the first hour of operation. This capacity can often exceed the average usage of most homes, but 75 gallon water heaters are very common in homes that have large jetted bathtubs. The capacity on that type of bathtub can vary, but on the larger end of the spectrum they can deplete a 50 gallon water heater just by themselves without even filling the bathtub all the way.

80 gallon water heater

This size of water heater is only used by electric water heaters. Prior to 2015 you used to be able to find conventional electric water heaters of this size. According to an addition to the National Appliance Energy Conservation Act (NAECA III) there are now energy standards in effect for all water heaters manufactured for sale in the United States. They require that any 80 gallon electric tank manufactured for domestic use be a hybrid heat pump water heater. See this page for more information about hybrid heat pump water heaters. Keep in mind that heat pump water heaters have different modes of operation, some are very efficient while others prioritize producing hot water faster. If the heat pump water heater is operating in a more efficient mode it will have a slower recovery rate. For this reason 80 gallon hybrid heat pump water heaters typically have a first hour rating in the 90 gallon range.

Sometimes people also want to be able to get more hot water out of their water heater. To accomplish this, they want to upsize their water heater. If your previous water heater met the code requirements there isn’t usually an issue with upsizing your water heater from a code perspective. However, you may still run into some difficulties upsizing your water heater. The first consideration is space. Water heaters with more water in them are typically wider than your current heater. Do you have room for this? Secondly, when you are upsizing your water heater, it will typically have a larger BTU (British Thermal Units) rating on the water heater. The larger BTU rating may require a larger vent. Re-doing your venting can be an expensive proposition, check with your installation coordinator to see if this will be necessary.

We Will Respect Your Busy Schedule!

We understand that getting a new water heater is rarely planned. At Faster Water Heater company, we always respect your schedule by arriving on time and getting your job done as quickly and efficiently as possible. Contact us today for a free estimate and get your hot showers back within a day.

(425) 636-7038