Difference Between Tank and Tankless

First, here’s a quick explanation about the differences between these two types of water heaters.

Depending on the size, a tank water heater holds up to 50 or so gallons of water. That water is heated in the tank and used for showers, washing dishes, doing the laundry, etc. As the water in the tank cools and/or the tank empties, it continually reheats the cooled water and/or refills with cold water that then needs to be heated.

A good thing to know about tank water heaters is that over time sediment from the water sitting in the tank settles at the bottom. Over time this sediment starts to build up.

So as the years go on, it’s possible to have so much build-up that a 50 gallon tank will hold only 30 gallons. This is why manufacturers recommend draining and flushing the tank once or twice a year to prevent this build-up.

A tankless water heater uses an energy source—electric or gas—and heats the water “on demand.” There’s no tank, so no stored water (and no need to flush or drain).

However, a common misunderstanding about tankless water heaters is that it provides “instant hot water.” But unless you have a hot water recirculation pump installed, this is not the case.

Because fresh water systems always have water in them, if you haven’t turned on the hot water in a while, the water in the pipe has cooled. So the cooled water runs out first when you turn on the hot water.

What you get with a tankless water heater is endless hot water, not instant.

What to Consider When Going Tankless?

Electric vs. gas – If your house is all electric with no ability for natural gas, forget it. It is our experience that electric tankless water heaters do not work for whole house water heating.

Installation – When converting from a tank to a tankless installation is the most important thing.

If the tankless water heater is not installed or set up properly, it will never work properly. As mentioned above, a tankless doesn’t have a tank so it heats the water on demand, or as water flow through the tankless water heater. And to heat the water on demand, significantly more natural gas supply is needed to the water heater than with a tank model.

Many people—including some plumbers—believe you can just swap out a tank for a tankless, and you are done. But this could not be further from the truth. In reality, if the tankless does not have the correct amount of gas supply hooked to it, it won’t work properly. Ever.

The venting of a tankless is also completely different than a tank, therefore requiring changes from tank to tankless, during the installation process. And without the right venting, a tankless unit won’t run as efficiently as intended and can shorten the lifespan of the unit.

Gas supply – An important question to consider is does your home gas system supply enough gas (considering other gas appliances you have in your home) to properly supply a tankless water heater. Make sure you take into account all the other gas powered appliances in your home. If not, there is really no way to properly install a tankless at all.

And a major concern is, will the average plumber spend the time to figure this out before installing the tankless? Our answer is no!

Price – The average cost of just the tankless water heater itself is 2 to 3 times more than a tank water heater.

Then add the cost of installation/converting everything correctly using a company with enough experience and a great reputation with tankless, and it’s now at least 3 to 4 times more—sometimes significantly more—than replacing and reinstalling a tank water heater.

Environmentally friendly/utility savings – Because tankless water heaters only heat on demand, you save on utilities which also makes it environmentally friendly. However the truth is the amount of savings over the life of the tankless will never even come close to the extra money paid for a tankless over a tank.

Lifespan and ongoing maintenance – It is important to note that a tankless water heater will only last as long as a regular tank water heater before it has to be replaced.

Now to be fair, the replacement should not cost as much as the initial installation/conversion—as long as the replacement uses the same gas supply or less than the converted one. But it absolutely will be more than a tank water heater.

Another important thing to note that many don’t always consider is the extra yearly maintenance a tankless water heater needs for it to continue working properly. And this maintenance must be done by a certified tankless specialist.

When Would we Recommend a Tankless?

Building a brand new home – It is our opinion that if you’re building a brand new home, it might not be a bad idea to install a tankless.

If you’re building a new home, it can be built to the tankless. This means it’s usually much less in front-end costs for the materials, labor and tankless installation compared to converting a home built with a tank.

However, we think there’s another really good option when building a new home. Instead of using a tankless water heater, build a room in the house for the tank water heater where the slab slopes to the outside only. Then if the tank water heater breaks, there is no possible damage inside the house. Not to mention, using a tank water heater is cheaper in the long run when you consider the overall costs of a tankless.