Getting the right-sized water heater for your San Jose home will ensure that there is sufficient hot water to meet your needs while at the same time making efficient use of energy. Before purchasing a water heater, talk to a water heating professional to ensure it is the right size.
Getting the Right-Sized Tankless or On-Demand Water Heater
A tankless water heater, also called an on-demand or instantaneous water heater, only provides hot water when needed. One benefit of this heater style is that it does not produce standby energy losses that you see with traditional storage water heaters. This could save you money on energy costs.
A tankless water heater provides hot water when the faucet is turned on. Cold water flows through the heat exchanger in the tankless unit. An electrical element or a natural gas burner will heat the water. The benefit of this unit type is that you don’t have to wait for a storage tank to fill up to get enough hot water. The downside is that there are limits to the output flow rate of the unit.
Tankless water heaters get rated by the maximum temperature rise that is possible based on the water’s flow rate. When determining the right size of tankless water heater for your home, you will have to evaluate both the flow rate and the temperature rise you will need. This will be different if you are trying to heat the water in your whole house or you’re using the unit for a remote application, for example, just in the bathroom.
The first thing to do is identify the number of different hot water devices you plan to use simultaneously. Then, calculate their total flow rate, which is typically gallons per minute. This is the number you will use when sizing your on-demand water heater.
For example, let’s say you intend to use a faucet with a .75-gallon per-minute flow rate and a showerhead with a 2.5-gallon per-minute flow rate. You would know that you are looking at a total flow rate of at least 3.25 gallons per minute. Next, you need to determine the temperature rise. You can do this by subtracting the water’s incoming temperature from the water’s desired output temperature.
In most cases, the incoming water temperature is around 50°F. Most people want the hot water in their home to be about 120°F. In this case, you will want your on-demand water heater to have a temperature rise of 70°F.
There is a slight exception when discussing dishwashers that don’t have internal heaters. In that case, you may want the water to rise up to 140°. This would mean that your desired temperature rise would be approximately 90°.
Most instantaneous water heaters are rated for different inlet temperatures. You will find that a 70°F water temperature rise is easily attainable at a flow rate of five gallons per minute if you have an on-demand unit heated with natural gas. You can attain the same temperature rise with an electrical unit, but your maximum flow rate is reduced to around two gallons per minute.
Another factor to consider when sizing a tankless unit is how far away the unit is from the most distant faucet. You want the unit to be able to produce sustainable hot water at the farthest faucet while at the same time not producing water that is so hot that it is scalding from the faucet that is closest to the unit. The best way to ensure accuracy when calculating the right size of tank for your home is to have your home’s plumbing system inspected by water heater technicians.
Sizing a Traditional Storage Water Heater
Conventional storage water heaters are North America’s most commonly used water heater type. A single-family stored water heater has a reservoir of between 20 to 80 gallons of hot water. This type of water heater releases hot water from the top of its tank when you open the hot water tap.
Cold water is pushed into the bottom of the tank through a dip tube, where it is heated. This ensures that the tank is always full. Most conventional storage water heaters use propane, natural gas, oil, or electricity to heat the water.
The water heater’s first-hour rating is used to size a conventional storage water heater for your home. The first-hour rating defines the number of gallons of hot water the heater can be supplied to a home within the first hour. This number will vary based on the heat source, tank capacity, and heating element size.
You want a water heater with a first-hour heating rating that matches your home’s peak demand. This is when you are using the most hot water. For example, in the morning, you might have multiple people using the shower, someone washing the dishes, and someone using hot water to wash clothes.
After determining what time of day you use the most amount of hot water, calculate the maximum usage of hot water during this one-hour time frame. Record this as your peak hour demand. You can create a chart outlining the number of gallons used during a peak hour for showering, shaving, washing dishes, washing clothes, etc. A water heater technician can work with you to help you determine when you use the most amount of water and the amount of water you use at your home’s peak time. This will help you better determine what size of unit and water heater model is right for you.
General Guidelines for Selecting the Right-Sized Traditional Water Heater for Your Home
When selecting a tank based on its first-hour rating, you should estimate 20 gallons of water for each person showering, 6 gallons of water for each person washing their hair, 2 gallons of water for each person washing their hands, 6 gallons of water for washing dishes by hand, 14 gallons of water for the dishwasher, and 30 gallons of water for washing clothes in the washing machine.
On average, a home with one or two people will be fine with a 23- to 36-gallon tank. With two to four people, it is recommended to get a 36- to 46-gallon tank. If three to five people are in the home, a 46- to 56-gallon tank is recommended. For each additional person, you must add 10 gallons to the tank size. For an average family of four, a 40-gallon water heater is more than enough to get the job done.
Work With a Top-Rated Plumber in San Jose
At Plumbtree Plumbing & Rooter, we have been helping residents in our area for years and are committed to being your neighborhood plumbing experts. We are proud to be the only plumber our customers need. We deliver high standards and workmanship at an affordable price.
Our services include general plumbing, installation, and maintenance. We work on new construction and remodels. We offer emergency and sewer services, install water heaters and plumbing features, and offer additional water services. Contact Plumbtree Plumbing & Rooter today and benefit from the experience that comes from working with your neighborhood plumbing experts.