How do I determine what tankless water heater I need?

A properly sized water heater will meet your household's hot water needs while operating more efficiently. Therefore, before purchasing a water heater, make sure it's the correct size.

With competitive price and timely delivery, Hitfar sincerely hope to be your supplier and partner.

Sizing Tankless Water Heaters

Sizing Solar Water Heaters

Sizing Storage and Heat Pump Water Heaters

&#; Subscribe to Energy Saver Updates

Here you'll find information about how to size these systems:

• Tankless or demand-type water heaters
• Solar water heating system
• Storage and heat pump (with tank) water heaters.

For sizing combination water and space heating systems -- including some heat pump systems, and tankless coil and indirect water heaters -- consult a qualified contractor.

If you haven't yet considered what type of water heater might be best for your home, learn more about selecting a new water heater.

Sizing Tankless or Demand-Type Water Heaters

Tankless or demand-type water heaters are rated by the maximum temperature rise possible at a given flow rate. Therefore, to size a demand water heater, you need to determine the flow rate and the temperature rise you'll need for its application (whole house or a remote application, such as just a bathroom) in your home.

1. List the number of hot water devices you expect to use at any one time.
    
2. Add up their flow rates (gallons per minute). This is the desired flow rate you'll want for the demand water heater. For example, let's say you expect to simultaneously run a hot water faucet with a flow rate of 0.75 gallons (2.84 liters) per minute and a shower head with a flow rate of 2.5 gallons (9.46 liters) per minute.
    
3. If you don&#;t know the flow rate, estimate it by holding a pan or bucket under the faucet or shower head and measure the flow for a minute. The flow rate through the demand water heater should be at least 3.25 gallons (12.3 liters) per minute. To reduce flow rates, install low-flow water fixtures.
    
4. To determine temperature rise, subtract the incoming water temperature from the desired output temperature. Unless you know otherwise, assume that the incoming water temperature is 50ºF (10ºC).
   
   You can also estimate the temperature by holding a thermometer under a cold-water faucet. For most uses, you'll want your water heated to 120ºF (49ºC). In this example, you'd need a demand water heater that produces a temperature rise of 70ºF (39ºC) for most uses.
   
   For dishwashers without internal heaters and other such applications, you might want your water heated at 140ºF (60ºC). In that case, you'll need a temperature rise of 90ºF (50ºC). Be cautious of a water temperature of 140ºF because it increases the possibility of scalding.

Most demand water heaters are rated for a variety of inlet temperatures. Typically, a 70ºF (39ºC) water temperature rise is possible at a flow rate of 5 gallons per minute through gas-fired demand water heaters and 2 gallons per minute through electric ones. Faster flow rates or cooler inlet temperatures can sometimes reduce the water temperature at the most distant faucet.

Some types of tankless water heaters are thermostatically controlled; they can vary their output temperature according to the water flow rate and inlet temperature.

Sizing Storage and Heat Pump (with Tank) Water Heaters

To properly size a storage water heater for your home -- including a heat pump water heater with a tank -- use the water heater's first hour rating. The first hour rating is the number of gallons of hot water the heater can supply per hour (starting with a tank full of hot water). It depends on the tank capacity, source of heat (burner or element), and the size of the burner or element.

The EnergyGuide label lists the first hour rating in the top left corner as "Capacity (first hour rating)." The Federal Trade Commission requires an EnergyGuide label on all new conventional storage water heaters but not on heat pump water heaters. Product literature from a manufacturer may also provide the first hour rating. Look for water heater models with a first hour rating that at least matches within your peak hour demand (the highest energy use during a single 1-hour period for your home).

To estimate your peak hour demand:

• Determine what time of day (morning, noon, evening) you use the highest amount of hot water in your home. Keep in mind the number of people living in your home.
• Use the worksheet below to estimate your maximum usage of hot water during this one-hour period of the day&#;this is your peak hour demand. Note: the worksheet does not estimate total daily hot water usage.

The worksheet example shows a total peak hour demand of 66 gallons. Therefore, this household would need a water heater model with a first hour rating of 66 gallons or more.

Worksheet for Estimating Peak Hour Demand/First Hour Rating * Use Average gallons of hot water per usage Times used during 1 hour Gallons used in 1 hour Shower 20 × = Shaving (.05 gallon per minute) 2 × = Hand dishwashing or food prep (2 gallons per minute) 3 × = Automatic dishwasher 7 × =

Clothes washer

× =  - Top-loader 25  - H-Axis 15 Total Peak Hour Demand = EXAMPLE 3 showers 20 × 3 = 60 1 shave 2 × 1 = 2 1 hand dishwashing 3 × 1 = 3 Peak Hour Demand = 66

*Estimates  are based on averages from a variety of information published on websites. Some water heater manufacturer websites also provide calculators based on the duration for the use case and other factors.

Want more information on induction tankless water heater? Feel free to contact us.

Making sure you have a properly sized water heater is very important. If your water heater is too small, your home won't have enough hot water to meet demand, which is an obvious inconvenience, and overloading the unit may cause premature wear and tear.

There's no benefit to oversizing a tankless water heater. If your tankless water heater is too large it will never operate up to full capacity, and the system may cost more than necessary.

Tankless Water Heater Size Calculator

Our free Navien water heater sizing tool, NaviSizer, is especially effective in helping people find the right size water heater for their project. 

Try NaviSizer

NaviSizer uses information you provide, including number of people in your household, number of bathrooms, fuel type and region (for local groundwater temperature) to help you choose the right size model.

How Tankless Water Heater Sizing Works

There are two primary factors to consider when determining the right size water heater.

The first is the maximum flow rate required by the hot water system, measured in gallons per minute (GPM). Maximum flow rate is determined by the number of fixtures (e.g. washing machine, dishwasher, shower) that will be used at the same time, and the flow rate of each. 

For example, if your home would use a dishwasher (2-3 GPM), a shower (2-3 GPM) and a washing machine using hot water (3-5 GPM) all at once, that would be a maximum flow rate of 7-11 GPM.

These are estimated flow rates - a licensed plumber can provide a more accurate estimate for the fixtures in your home. Your water pipe sizing, especially the incoming water supply, can also affect flow volume.

Temperature rise is the other critical factor. Temperature rise is simply the difference between the desired temperature setting of the water heater and the inlet water temperature.

For example, if the hot water temperature is set to 120°F and if the incoming water temperature is 55°F the resulting temperature rise is 65 degrees (120-55=65).

Typically, residential hot water temperature settings are 120°F or 125°F, and commercial temperatures can range from 140°F to 180°F, depending on the application.

Since incoming water supply temperature can vary based on the season, temperature rise should be calculated based on the coldest days of the year.

When you you know the required flow rate and the temperature rise, you can compare them to the tankless water heater output.

You can find this information on each Navien tankless water heater model page on our website, in the QuickFacts section under Temperature Rise. Maximum flow rate can also be found in the QuickFacts download for each model.

Domestic Hot Water (DHW) Capacity

Tankless water heater capacity is rated based on the gas energy input, which is given in BTU/h (British Thermal Units per hour). You&#;ll see this measurement when comparing different models of Navien tankless water heaters.  The higher BTU, the greater the maximum flow a tankless unit can produce.

If you want to learn more, please visit our website Gold & Platinum Melting Furnace.