Series Vs Parallel Water Heater – Which One is Right for You?

The main difference between the series and parallel water heater is its functions. In a series water heater, heating begins with the first water tank and continues until all of the tanks have been heated. But in a parallel water heater, all of the tanks are set to operate altogether parallel.

This article will cover the differences between series vs parallel water heater. And in the end, you will find which one will be best for you.

Series Vs Parallel Water Heater Comparison

Comparison PointSeries Water HeaterParallel Water Heater
Temperature in each tankRemains sameCan be at different temperature
Ease of InstallationEasier to installChallenging to install compared to series
AffordabilityMore affordable when water requirement is hugeAffordable when water requirement is less
LifespanHave longer lifespanHave shorter lifespan
Energy-EfficientLess energy-efficientMore energy-efficient

Functioning – the Major Difference

When water heaters are in series, the water heater heats the water in the first water tank. The water then flows to the next water tank, and the water heater heats that water. This system continues until the water reaches the last water tank.

However, in a series water heater system, all water tanks must be at the same temperature for the system to work correctly.

When water heaters are parallel, each water heater heats its water. In a parallel water heater system, each water tank can be at a different temperature. It is helpful if you want to use one of your water tanks for a different purpose than the others. For example, you could have one tank for drinking water and another for dishes.

Wiring Diagram

Water tanks must be of equal capacity while wiring water heater in a series. The water heater with the smallest tank should be at the beginning of the series, and the water heater with the largest tank should be at the end of the series. The water heaters in between will have progressively larger tanks.

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Wiring water heaters in parallel is slightly more complicated. When water heaters are wired in parallel, the water tanks must be the same size, and water heaters should be placed next to each other with no water heaters between them.

Ease of Installation- Series or Parallel Water Heater

You will find each tank connected to the next one in line with water heaters in series. It means that the water heater will only be as powerful as the weakest tank in the line. If one of the tanks fails, then the entire system goes down.

On the other hand, water heaters in parallel are connected side by side. It allows each tank to function independently, so the others will continue to operate if one fails. However, water heaters in parallel are typically more expensive and take up more space.

When it comes to consider the ease of installation between water heater in series vs parallel, heaters in series are usually easier to install. There is only one pipe that needs to be connected to the water heater. With water heaters in parallel, each tank has its pipe, making the installation process a little more complicated.


Which one is more efficient? Water tanks in series or parallel? Water tanks in series are more efficient because the heated water from the first tank circulates through the second tank. This way, you don’t lose any heated water as it passes through the pipes.

In contrast, water tanks in parallel are less efficient because each tank heats up independently of the other. As a result, some of the heated water is lost as it travels between the tanks.

Again, the water flows through one tank after another in a series system. It is a more efficient option if you have a large home and need multiple tanks to provide enough hot water for everyone.

In a parallel system, two or more tanks are linked together. It allows the tanks to share the workload, making them more energy-efficient overall.

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When you are hovering between a water heater in parallel or series, the lifespan of a series water heater is typically longer than that of a water heater in parallel. The water tanks in series are offset, so if one tank leaks, the other will still have water. With water heaters in parallel, the entire system will be without water if one tank leaks.

Additionally, each tank can be different when water heaters are in series. It is helpful if one water tank is larger than the other, accommodating more water. When water heaters are parallel, both water tanks must be the same size.

However, before buying that water heater in series or parallel, keep in mind that using gas is a more efficient and longer lifespan. Electric water heaters are cheaper to purchase, but their demand for continuous electric supply limits their use in some areas. Moreover, they have a shorter lifespan than water heaters that use gas.

Water Heater Tank Preference-Series or Parallel

Water tanks in series heat water one at a time. The water from the first tank is heated and then sent to the second tank, and so on. This system is suitable for homes with limited water storage space.

Contrarily, the water heater in parallel heats water simultaneously. The water from each tank is heated and then combined. This system is suitable for large homes that quickly need a lot of hot water. It’s also ideal for homes with two water heaters because it can provide backup if one water heater fails.

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Frequently Asked Questions (FAQs)

Can you put water heaters in series?

Yes, but keep in mind that the heater with the maximum input should be placed at the beginning of the series when installing water heaters in series.

Can you parallel hot water tanks?

Yes, you can parallel 2 or more than two water heaters. And you see the water tanks when connected in parallel can provide more water than that of connected in a series connection.

Can you put tankless water heaters in parallel?

Yes, two tankless heaters can be put together to produce a greater amount of hot water on demand. You could also use more tankless units in parallel for a greater flow rate.

Can you run tankless water heaters in series?

Yes, to produce more hot water on demand, you can run two tankless water heater I series. Even, it will give better result if we compare 2 tankless water heaters in series or parallel.

Which Water Heater Setup Is for You?

Series water heaters are usually used in commercial settings, as they allow for more water storage capacity. In a series water heater set up, each tank is connected to the one before it so that water flows through them in sequential order. If one tank fails, the whole system shuts down.

Parallel water heaters are more common in residential settings. In a parallel water heater set up, each tank is independent of the others, meaning that if one tank fails, the others still operate. It also means that you can use only some of the tanks if you’d need all of the water heated at once.

Which water heater setup is right for you between series vs parallel water heaters? It depends on your needs. If you need a lot of water storage capacity, go with a series water heater. If you’re looking for a more flexible option that you can tailor to your specific needs, go with a parallel water heater.

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