It is important that you get the sizing of your water heater right. If your water heater is too small for your family, you will not have enough hot water to meet your needs. If your water heater is too big, you will be wasting money on energy costs.
There are a few factors that you need to take into account when sizing a water heater. If your current water heater is not the right size, a replacement can solve the problems associated with it. If you need help, you can always consult with the professionals at Rooter-Man Plumbers.
What Happens if My Water Heater is Not The Right Size?
The needs of your household are the primary factor in sizing your water heater. When your water heater is too large or too small for your home, there will be problems.
Undersized Water Heater
When you have a tank water heater that is too small for your household, you will find that you run out of hot water quickly. It is either the water heater was undersized during installation or the hot water needs of your household have grown. This can be a problem if you have a family or entertain guests often. If you have an undersized water heater, it is important to upgrade to a larger model.
If you have a tankless water heater that is too small, you may not run out of hot water. However, the flow rate through the taps will diminish. This can be frustrating and cause you to take shorter showers.
Oversized Water Heater
An oversized water heater is not as big of a problem as an undersized one. However, you will be wasting money on your energy bill. When a tank water heater is oversized, it will heat the water too quickly and then cycle off. It will have to turn back on again shortly after to reheat the water. This wastes a lot of energy and increases your utility costs.
A tankless water heater that is oversized will not have to cycle on and off as often. However, it will still be using a lot of energy to heat the water. This means that you will see an increase in your energy bill.
Since larger water heaters are more expensive, you will also be wasting money on the initial purchase.
How to Size Your Water Heater
Tank and tankless water heaters are sized differently. Tank water heaters are sized based on the number of gallons of hot water they can produce in an hour. This is known as first hour rating (FHR). Tankless water heaters are sized based on how many gallons per minute (GPM) of hot water they can produce.
Another important rating for water heaters is the British Thermal Unit (BTU) rating. The BTU rating of a water heater tells how much energy it requires to heat a pound of water by one degree. Most residential gas water heaters have a BTU rating of between 30,000 and 40,000 BTUs per hour.
The appropriate BTU rating for your home is determined by the incoming hot water temperatures and your favored water temperature. Since water comes into your unit colder in winter, you should choose a new water heater with a BTU rating that is appropriate for wintertime water heating in your city. This ensures you have adequate hot water all year round.
How to Size Tank Water Heaters
To get the right size tank water heater for your home, a professional plumber will first determine your household’s peak hour demand. This is the amount of hot water you consume at the hour of the day when your family is using the most hot water. It is measured in gallons per hour (gph).
To calculate your household’s peak hour demand, your plumber will consider certain factors;
- How many people live in your home: The more people in your home, the more hot water you will need.
- The number and types of appliances that use hot water: Dishwashers, clothes washers, and showers use the most hot water.
- How long each appliance is used: The longer each appliance is used, the more hot water it will require.
- What hot water required activities take place in your household: Bathing, cooking, and laundry all require hot water.
- When do you prefer to carry out these activities?: Do some of you shower in the morning and others at other times of the day?
- Do these activities take place at the same time?: Do members of your household use multiple showers at the same time?
- How do you perform these activities?: Do you take long showers or spend long hours in a tub filled to the brim?
With this information, your plumber is able to estimate the average volume of hot water used during the peak hour. A total of the estimates reveals your household’s peak hour demand.
The right size water heater for your home should have a first hour rating (FHR) that is a little lower than your peak hour demand. This way, your new water heater will have enough hot water to meet your household’s needs during the peak hour without having to cycle on and off too often.
How to Size Tankless Water Heaters
Tankless water heaters produce hot water as required in the household. That is why they are referred to as on-demand water heaters. To size tankless water heaters requires two parameters, the flow rate and temperature rise.
- Flow rate: This is the rate at which water flows through a fixture in use. It is measured in gallons per minute (GPM).
- Temperature rise: This is the difference between the temperature of the incoming water and the temperature of the outgoing hot water. It is measured in degrees Fahrenheit.
To determine your household’s flow rate, your plumber will add the flow rates of all the fixtures that will be in use at the same time. To get the temperature rise, your plumber measures incoming water temperature and considers your preferences and safety requirements o determine output water temperature.
Using these figures, your plumber is able to determine the flow rate and temperature rise required. With this information, he can size a tankless water heater that is able to meet your household’s hot water needs.
Sizing Estimates For Water Heaters
Although it is best to get a professional plumber when you need a new water heater, there are general estimates that you can keep in mind. Based on household size, here are rough estimates that can guide you in your water heater selection;
Tank Water Heater Sizing Estimates
- Households of 1 to 2 people: 30-gallon water heater.
- Households of 2 to 3 people: 40-gallon water heater.
- Households of 3 to 4 people: 50-gallon electric water heater or 40-gallon natural gas or liquid propane water heater.
- Households of 5 or more people: 80-gallon electric water heater or 50-gallon natural gas or liquid propane water heater.
Tankless Water Heater Sizing Estimates
Tankless water heaters are sized differently from tank water heaters. They do not have a storage capacity like tanks and so the size is dependent on the flow rate and temperature rise.
- For 1 to 2 fixtures at the same time: Minimum flow rate should be 3.5GPM.
- For 2 to 3 fixtures at the same time: Minimum flow rate should be 5GPM.
- For 3 to 4 fixtures at the same time: Minimum flow rate should be 7GPM,
- For 5 or more fixtures at the same time: You may need more than one tankless water heater unit.
We Can Help You Select The Right Size Water Heater
Whether you are looking for a tank or tankless water heater, our experts at Rooter-Man Plumbers can help you select the right size water heater for your home. We will take into consideration all the factors that affect your hot water consumption and recommend a unit that is able to meet your household’s needs. Contact us today at 281.351.4422 for all your water heater needs.