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Are Two Water Heaters More Efficient Than One?

Traditional water heaters usually have a large storage tank to conserve hot water. But as they need to run continuously, the energy cost rises quickly. Installing two tankless heaters usually deliver slightly reduced water flow.

So, are two water heaters more efficient than one? Yes, they are. The energy loss during standby is higher in one water heater. If you use two water heaters for small homes, they will save up to 35% of energy costs. The savings will drop to 14% if you use dual heaters for large homes.

Let’s know more about the upfront cost and long-term savings of two water heaters instead of one.

How Does a Traditional Water Heater Work?

These water heaters are mostly used for small to medium families. They have a storage tank of twenty to eighty gallons, depending on the requirement of the family. The heater usually runs on gas or electricity. Gas burners or electric elements heat the water in the tank.

When you turn the water faucet on, hot water flows to the faucet from the tank. And the empty space inside the tank is filled with cold water, and the heater continues to heat up the water. This way, you receive hot water instantly.

tank water heater work image

But the problem with these heaters is they waste a lot of energy. For example, the heater will run until the water temperature has reached a certain level. If you don’t use the hot water for a while, the water temperature will drop.

Once the temperature drops, the heater will start working automatically to keep the temperature constant.

This is where traditional water heaters waste the most energy. Though the energy loss can be reduced with proper insulation, it is still pretty high compared to tankless water heaters.

How Does a Tankless Water Heater Work?

These water heaters don’t have a storage tank. Instead, they only have a heating element, and water flows through that element. When you turn the water faucet on, the water goes into the heating chamber and gets heated up.

In this method, you might not get hot water instantly. But the heater will only run when you need water. This way, it saves a lot of energy. However, as these heaters are smaller compared to traditional heaters, homes with higher requirements can install two or more heaters.

What Are the Benefits of Two Water Heaters?

Installing two water heaters can give you several benefits. Check them below.

  • Dual water heaters are more suitable for small to large homes. If a home has a 40-gallon water heater, two water heaters can replace the system. And they will save up to 35% of energy cost that is wasted during standby.

Though the energy loss reduces in water heaters with 80-gallon or bigger water tanks, two water heaters are still better.

  • Using two heaters can deliver hot water faster than one heater. If you use one heater, the water needs to travel larger distances to reach remote fixtures. But two heaters reduce the distance and provide hot water faster.
  • When one heater is on, the water waste is higher until the temperature rises. But if you install two heaters, the heating time reduces. As a result, you need to drain water for a shorter period.
  • Having one water heater might not be enough for emergencies. If the heater fails, you won’t have hot water at your disposal. When two systems work together, one can still work if the other is faulty.
  • The service life of two tankless water heaters will be over twenty years. On the other hand, traditional water heaters have a service life of about fifteen years.

What Are the Drawbacks of Two Water Heaters?

Despite better efficiency, two water heaters of tankless type can cause some issues. Here is a quick overview.

  • The biggest disadvantage of installing two water heaters is the upfront cost. Each tankless heater can cost up to $4,000, which multiplies when you have two or more heaters. Additional costs for installation and accessories also rise accordingly.
  • One traditional water heater can deliver 8-10 gallons of water per minute. But the capacity of a tankless water heater is much lower. Even if you use two heaters, they will hardly deliver about 8 gallons per minute.

Which Should I Choose: One or Two Water Heaters?

A traditional water heater with a large storage tank is more suitable when it comes to having hot water instantly. But they waste a lot of energy maintaining the water temperature.

On the other hand, tankless heaters are more energy efficient than traditional heaters. You can install multiple units at convenient points to reduce the waiting time and save on energy costs.

Although multiple units cost a lot to install, their efficiency and service life will compensate down the lane. So, you should choose two smaller tankless heaters instead of a big traditional one.


Check the answers to commonly asked questions.

1. Do I really need two water heaters?

In large houses, fixtures can have a huge distance from the heater. So, you might need two or more heaters to quickly get hot water.

2. Can you run two water heaters together?

Yes, two water heaters can run together. They can be installed in series or parallel, which affects the performance.

3. How many water heaters do I need for two showers?

If there isn’t any other appliance, one heater should be okay. But if you have more appliances, you might need two water heaters.


Efficiency is one of the most significant reasons behind the popularity of multiple water heaters. As traditional single-tank heaters take up a lot of space and consume more energy, they aren’t suitable for homes with less frequent use.

Installing two water heaters lets you get hot water faster without keeping the heater on all the time. Though multiple heaters can be more expensive than one heater, the cost will be balanced throughout the service life. And you will also enjoy an extended service life with two heaters.