water heaters

The water heater size you will need can be different depending on your lifestyle and whether you get a tank or tankless water heater. A water heater that is too big or too small can affect your hot water quality and quantity, affecting the efficiency of the water heater.

water heaters

A water heater that’s too small will likely lead to a lack of hot water within a short amount of time, which can also overwork your water heater as well and potentially decrease its lifespan. However, a water heater that’s too big can cost you a lot in energy bills, along with wasting a significant amount of unnecessary energy.

Whether your water heater is too big, and your energy bills cost more now than they should, or it is too small, and you run out of hot water way quicker than expected, you will want to get it replaced with an appropriate-sized water heater that meets the demands that you need it for.

What is the Capacity of a Water Heater Measured In?

Water heater capacity is measured by the gallon. The total load capacity calculates how much hot water can be used in a single hour. However, your water heater’s capacity can change, depending on the energy efficiency of the water heater and the size of the water heater, as well as personal hot water usage amounts (e.g., showering).

Hot water heaters have an optimal energy point based on size and usage. A higher energy-efficient model statistically may give you a higher hot water capacity than a less efficient, bigger sized one will, but your water usage can still have an impact on the total load capacity.

Sizes for Tank Water Heaters

Tank Water Heater Size

The sizes for tank water heaters will vary between 20 gallons all the way to 75 or 100 gallons for residential tanks, depending on what company you are purchasing from. Typically a 40-gallon water heater will suffice for a family of 4 with normal usage.

The size your family needs for a tank water heater is subject to your daily water usage and the efficiency level of the water heater you use. Some will be more efficient than others so the greater your water heater’s efficiency level, the smaller the size needs to be.

Sizes for Tankless Water Heaters

Tankless Water Heater Size

The sizes for tankless water heaters change based on the amount of hot water demand you will need and the gallons per minute flows of the appliances you have that use hot water. This is the main reason why many people end up having issues with their tankless water heaters: because they will get one that is not big enough for the high water output times that they will use.

The highest gallon per minute tankless water heaters you will be able to purchase are around 10 GPM, while the smallest is around 2 or 3 GPM. With this, you can choose to get either gas or electric tankless systems and decide what rooms and appliances will have access to the hot water. You could also choose to get a couple of bigger tankless water heaters instead to service the entire house.

There are many factors to take into account when looking into the sizes for tankless water heaters; determining this will take some time and help you have more consistent hot water for specific areas of your house and potentially save you space in your house too.

Sizes for Solar Water Heating System

Solar Water Heater Size

The smallest solar water heater systems can be as small as 5 gallons but can be as big as over 100 gallons.

Similar to the tankless, these will take more initial figures and input that is more specific for your situation than a tank water heater will need. Because of how the solar water heater stores its water, it will take more time to heat the water than other water heaters.

It is also based on how much sun exposure your state and your house get and how efficient your system is and how much hot water you would like to have.

For example, the size of a solar water heater for a family of 4 can be anywhere from an 80-gallon to a 100-gallon system to ensure there is enough hot water for peak times, due to how much sun is available each day.

There are charts and averages available for figuring out the different water heater sizes and which one you need based on your household. However, you will want to consult with your installer along with data on how much hot water usage you consume each day to make sure these chart averages apply to your situation.

How Much Hot Water Do Daily Routines Take?

How Much Hot Water Do Daily Routines Take?

Most water you use throughout each day ends up being used for daily routines such as dishes and showering.

If you want to use less hot water, some appliances allow you to control and adjust the temperature settings, but not all appliances are capable of this without costly upgrades. Knowing how much hot water your daily chores and habits consume will help you figure out the amount of hot water you need to choose the proper size water heater you need.

On average, Americans use 100-175 gallons a day per individual. This can fluctuate depending on your location and how much you use. Here is a rough estimate of how much water different chores and tasks will take:

Washing Machine Water Usage Average

This is based on how old your washing machine is. Using cold water for your washing machine will help save on energy bills and heating costs overall.

Normally, the machine you have can be searched to find the gpm if it is not stated on any labels on the machine.

Bathing Water Usage Average

This will depend on how full of a bathtub you fill, but an average tub can hold anywhere from a maximum of 15 – 30 gallons of water.

You can figure out how much you use by measuring the flow rate. To measure this, take a timer and an empty gallon jug, and then turn the water on and track how many seconds it takes to fill up the gallon. Then using that flow rate, you can estimate how much water you use in your bathtub by counting how long it takes to fill the tub and dividing that by the flow rate.

Showering Water usage Average

A shower can save hot water overall, but it can also end up consuming more water too, depending on how long a shower you take. The gallons per minute a shower will produce depends on the showerhead. Some can be as low as 1-1.5 GPM but the industry standard for new shower heads is 2.5 GPM. To get an idea for reference, a 10-minute shower will produce 10-25 gallons of hot water usage.

You can use the flow rate as mentioned above to determine how much water you use in the shower.

Dishwasher Water Usage Average

A dishwasher will use about 4 – 10 gallons per use, depending on the model and settings.

To determine how much water is used, you will have to check the model information in the manual or search it online if it is not labeled on the dishwasher.

Washing dishes by hand Water Usage Average

The amount of water used when washing dishes by hand will vary greatly. If you have an efficient dishwasher, it may be best just to do a quick scrub to make sure food is off of plates right away and leave the rest of the work up to the dishwasher.

The water usage can be as low as 2 gallons for more efficient models, but it could be 27 gallons. Depending on how hot water is used here causes a big difference in hot water costs.

Measuring how much hot water you use to wash dishes by hand will be trickier to measure since you are likely to constantly change the water pressure by turning the water on and off, or higher and lower.

At most, you will likely use 1.5 gallons per minute. However, this is also an easier way to adjust your hot water usage, as you have more control over how much water you use. Keeping your water pressure lower for easy-to-clean plates is one way to reduce your hot water usage.

Shaving Water Usage Average

Shaving tends to use the smallest amounts of hot water in your home if you shave in the sink. If you shave in the shower, you will consume more water because of the higher water pressure and if you keep your water running while shaving. Where you shave and how much you shave can also make a difference in how much water you use.

This can be as little as half a gallon of water used to as much as 10 gallons for shaving a face. For other areas, this could be more or less.

Washing hands Water Usage Average

This will consistently be one of the lower hot water usages in your home. On average, this will consume about 0.5 – 2 gallons of water daily, depending on how long you have the water on when washing your hands.

To reduce usage, try to use the water at a lower pressure or if you can turn it off while soaping up your hands.

Frequently Asked Questions

Is a 50-Gallon Water Heater Big Enough for a Family of 4?

In most cases, a 50-gallon water heater should be big enough for a family of 4. However, depending on your family’s water usage, you may want to install a larger tank.
With moderate use though, a 50-gallon water heater should work. It’ll also be easier and cheaper to install and be able to heat up quicker.

What Size of Tankless Water Heater Do I Need for a Family of 5?

For a family of 5, you will most likely need an 8-10 GPM tankless water heater for the entire house (and depending on how cold your geographical location is, maybe a second one). You could also use multiple smaller ones at the sources you want it for if you want smaller, more direct lines for hot water. Unlike a water heater tank, where you can estimate what size you need based on the number of people using the hot water, a tankless water heater takes more calculations to figure out. This can be a worthwhile investment if you want to have less energy loss from heating water.

Final Thoughts

The size of the water heater you need will change for almost every individual household’s needs. From the simplest and least time-consuming needs with a tank water heater to the more complex demands with a tankless or solar water heater, they all have their places where they shine and have their full potential.

Sometimes if you are not getting enough hot water from your current system, one or two simple changes in daily habits and hot water usage can make all the difference when it comes to reducing costs and conserving energy.

Try a few adjustments to your routines before spending money on a new system. If you do end up needing a new system, though, opt for more efficient brands. It will do you better in the long run.

Written By: Andrew Miles
Written By: Andrew Miles

30-year licensed plumber out of NYC. Specializing in Water Filteration and Softening Systems. Now, retired and enjoy sharing my industry knowledge here. See my bio.

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