Water Heater Sizes

Water heater comes in various sizes. This may not seem important, but choosing the right water heater size is very crucial if you want to make the most out of your water heating system and utility bill.

Determining The Right Hot Water Heater Size For Your Demand

The demand in hot water is at its highest during shower time. As a rule, a good water heater tank should still have hot water even after a couple of people have showered. With tankless hot water heaters, the size of the tank does not matter, since they do not have tanks. Nevertheless, the FHR or first hour rating is what matters, especially in tankless heaters. Tank heaters also have FHR and with a high First Hour Rating, the performance of the heater should be good enough regardless of the tank size.

For conventional tank water heaters, the right size for your home needs is determined by the number of hot water fixtures your household has. For tankless systems, you can determine the water heater size by calculating the amount of hot water needed at a time. This is referred to as the flow rate, which is measured as gpm or gallons per minute.

To determine the gallons of hot water you need per minute, get the total gpm of the appliances and fixtures that you might possibly use at the same time. For instance,  if you usually run a 1.5 gpm kitchen faucet and a 2.5 gpm dishwasher simultaneously, then you’ll need 4.0 gpm of hot water.  

Factors To Consider When Choosing the Right Size of Water Heater

When looking for the perfect water heater size, you also need to know if you are using it as a whole house system or a point-of-use system. In general, traditional tank heaters are made to serve as a whole house system, which sends hot water throughout the areas in the house where hot water is needed. Tankless hot water heaters usually serve as whole house systems, too, since they heat water as required.

On the other hand, point-of-use water heating systems are separate units, which are directly installed in a closet or under the sink. This type of water heating system provides hot water to a particular location instantly. Most of the time, point-of-use heaters are installed to augment an existing system.

Once you’ve considered which type of system to use, you can now decide on the water heater size to install. It is crucial to pick a water heating system that gives you ample hot water supply to suit your needs.

Here are a couple of facts about water heater sizes:

• Installing a tank water heater that has a larger capacity than you actually need will make you pay more than you actually use. With larger tanks, you will heat more water, which could possibly end up wasted.
• Using a system with a capacity smaller than your hot water requirement could lead to shower time rationing. An undersized heater also has a shorter lifespan, since it works much harder.

Hot Water Requirement	Number of Residents	Tank Size (Electric)	Tank Size (Gas)	Tank Size (Oil)
Vacation Home – no washing machine - no dishwasher	1-2	30 gallons	20 gallons	20 gallons
Small to Medium-Sized Family Home – 1 toilet and bath – no dishwasher – with washing machine	2	40 gallons	30 gallons	30 gallons
Medium-sized Family Home – 1 and a half bathrooms – with dishwasher – with washing machine	3	50 gallons	40 gallons	30 gallons
Medium to Large-Sized Family Home – 2 full bathrooms – with dishwasher – with heavy-duty washing machine	4	65 gallons	40 gallons	40 gallons
Large-Sized Family Home – more than 2 bathrooms – with dishwasher – with heavy-duty washing machine	5	80 gallons	50 gallons	50 gallons
Large-Sized Family Home – more than 2 bathrooms – with dishwasher – with heavy-duty washing machine – whirlpool baths	6	120 gallons	75 gallons	75 gallons