Tankless hot water?

If your current hot water heater is getting old or starting to experience issues, it may be a good time to consider switching to a tankless hot water system. Also known as an on-demand or instant water heater, they heat the water only when it is needed. A conventional tank water heater keeps heated water stored in a tank. The tankless option eliminates this need for a large storage tank. This saves on space and it reduces energy consumption by not heating and reheating water continuously.

According to energy.gov, for homes that use 41 gallons or less of hot water daily, a tankless water heater can be 24%–34% more energy efficient than a conventional storage tank water heater. They can be 8%–14% more energy efficient for homes that use a lot of hot water -- around 86 gallons per day.

Tankless water heaters may use either electricity or gas as a fuel source. 

Electric tankless water heaters heat water using thick copper wire rods. They’re less expensive than gas fueled heaters but are not as efficient. They may have a difficult time providing hot water to multiple appliances at the same time. You also might need to upgrade your electrical system to handle one of these.

Electric tankless water heaters are better suited for smaller households, and regions with warmer groundwater temperatures.

Gas tankless water heaters burn either propane or natural gas. They are a better option for larger households or areas where gas is a more accessible and affordable energy option.

There are two types of gas tankless water heaters: non-condensing or condensing.

Non-condensing tankless water heaters have a single heat exchanger. The water flows through the exchanger, any unused exhaust heat releases through a vent. They’re less expensive than condensing units, but the metal venting they require because of their higher exhaust temperatures can raise the total installation cost. They also aren’t as efficient as condensing heaters because they don’t use recycled heat from the exhaust to warm your water.

A condensing tankless water heater traps condensation and then recycles it to heat water rather than releasing it into the atmosphere. It can also collect the heat from exhaust gasses by using an additional heat exchanger. The benefit of using a condensing tankless water heater is greater energy efficiency, resulting in lower costs. Another advantage is that your options for ventilation are less expensive since the exhaust from the system is cooler.

How does a tankless water heater work? When a hot water tap is turned-on, cold-water flows into the unit. The heater’s sensors detect the water flow and activate the heating process.  The water is then heated instantly by either a gas burner or an electric element. The unit adjusts the power output to maintain the desired hot water temperature. This allows for a continuous supply of hot water, as long as the demand does not exceed the unit’s capacity.

Pros of tankless water heaters

Continuous hot water supply

Because they provide on demand hot water, you won’t be stuck with only cold water and icy showers if you’re the last one up in the morning. With a conventional tank heater, the amount of hot water available at any given time is limited to what is heated and stored in the tank.

Energy efficiency

Because tankless water heaters only turn on when hot water is needed, they use less electricity or gas than a tank heater that has to maintain a full tank of water at a specific temperature 24 hours a day. This saves on energy costs.

Space-saving design

If you’re short on space, a tankless water heater is a great option. These units are much smaller than conventional storage tank water heaters and can be installed on a wall where you can easily reach them to perform maintenance.

Longer lifespan

Tank water heaters typically last only 10–15 years, whereas tankless versions usually last over 20.

Better temperature control

Many tankless water heaters have advanced thermostatic controls, allowing you to set and maintain precise water output temperatures. This is particularly helpful for households with young children or elderly members at risk of scalding.

What size tankless water heater do you need?

Evaluating your household’s hot water requirements is a crucial step when considering a tankless water heater. These heaters can generally deliver between two and ten gallons of hot water per minute. This may seem like an unlimited supply for many households. However, without the right size unit it is possible for demand to exceed capacity.

Understanding your desired flow rate (GPM) and temperature rise (ΔT) are critical to selecting the right size tankless water heater. The flow rate is the sum of the flow rates of all hot water devices expected to be in use at the same time. The required temperature rise is calculated by subtracting the incoming water temperature from the target output temperature.

Below are some average flow rates of common appliances

Dishwasher: 1–2.5 GPM

Kitchen or bath faucet: 1.5–2.2 GPM

Showerhead: 1.25–2.5 GPM

Tub filler faucet: 4 GPM

Washing machine: 1.5–3 GPM

Typical flow rates for a gas tankless water heater are around 5 to 10 gallons per minute, while electric tankless water heaters usually have lower flow rates of 2 to 5 gallons per minute. Most units will accommodate two to three people taking showers simultaneously with newer low flow shower heads.

Measure the incoming water temperature with a thermometer. Subtract that number from your desired output temperature (usually about 120 degrees Fahrenheit) to get the temperature rise that you are looking for.

Evaluate the specifications on your various tankless water heater options to your expected flow rates and desired temperature rise to find the correct size for your household.

While tankless water heaters generally cost less for daily operation, the initial installation costs are higher than those of a conventional tank water heater. Your existing water lines and gas or electric supply need to be reconfigured to accommodate a tankless water heater, and you might need to upgrade your electrical panel before installing the unit.

Regular maintenance is also necessary to keep your tankless water heater in top condition. Even with the best tankless water heater, you should expect to pay a few hundred dollars annually maintaining it for optimal performance. Flushing the system, checking for scale build-up, and replacing any worn parts will extend the life of your unit and help it maintain its efficiency.

For homes with multiple showers, appliances, and fixtures that require hot water simultaneously, a single tankless water heater may not be sufficient to provide enough heated water at all times. Installing several units is an option.

Point-of-use tankless water heaters are also available. These point–of–use systems are smaller and specific to particular fixtures or appliances, such as a single shower or faucet.

Elbert Heating & Air will be happy to discuss your tankless hot water options and pricing in more detail. Just give us a call.