Can you install an electric tankless water heater in the same line as a gas tank water heater. We have a small gas water heater that runs out of hot water with the first shower. I was thinking of adding a small tankless water heater in the line to heat the water prior to filling the gas water heater. My hypothesis is that we would always have hot showers and we would be able to use more than one hot water application at once without a problem. What do you think?

Yes you sure can, just be sure that the tankless is properly sized.

a small electric tankless would be useless. they don't put out enough to do what you want to do.

change your shower head to something with a lower GPM rating.

why not just upsize your gas water heater?

The entrance to the basement is too small for a larger tank to fit through

would a tankless water heater not more quickly fill the gas water heater tank with hot water?

Yes, as long as it is sized correctly.

might be better to put the tankless after the water heater, and use the gas as preheat.. then electric would only come on when required. So if hot water is going through it it wouldn't spin the power bill. If the electric is first..its always going to run. The ones Ive seen for probably what you are looking for could be 3 elements which is 3 50 amp breakers, that's what the steibel eltron ones required.

If you take a good look at the electric requirements for electric tanklesses, you may change your mind. They tend to use massive amounts of electricity, for mediocre results.

Have a look at the Seisco Supercharger! This is a small electric tankless designed to be used as a booster for tank water heaters and basically doubles the capacity of the tank. Rember that if you use something like this down stream of the tank, you are not asking it to heat 50*F ground water. You are asking it to BOOST what will be around 100* water, or 95* or whatever as you run out of hot water in the tank until it too can't keep up. This typically doubles the capacity of a tank per draw. Google it and check it out.

Paul and Packy. Things are changing in the tankless industry very quickly. This particular model is a 9kw, 30 amp max unit that takes a single 40 amp breaker. It comes on based on temperture NOT FLOW. When it does come on it fires at around 6 amps and ramps up from there avoiding the big slam to the panel and also providing for better temperture control. So typically you would set the Seisco Supercharger at 115* and have the ank around 120-ish. At 114.9* the supercharger is going to wake up and start doing it's job keeping the water at 115* for as long as it can.

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Scott....I'm not opposed to tankless units. I don't know about the electric rates in NC, but using an electric "booster" of sorts, attached to a gas water heater,here in CT, would not be very economical. To the OP....Remember, the water stored in a water heater should be stored at 140*, to kill any dangerous bacteria. Use a thermostatic mixing valve after the tank to prevent anyone from being scalded.

Most homes here in VA are still keeping them around 120-125, but either way, the idea in this case is not so much economics, it's capacity without making major changes or going to larger tanks. Remember in this case we are only asking these "boosters" to raise the temperture a few degrees so the homeowner can finish whatever they are doing at the time. when the tank is not out of hot water these machines don't use any energy at all so the increase in energy use is only what is needed to satsify those peak demands. (instead of keeping a bigger tank hot all the time)

If you set a tank at 140 you still have to have a Mixing valve to knock it down to a safe temp so this booster would still work just fine and still increase the capacity of the tank without a major tankless or tank upgrade. This kind of creates a hybrid system to increase capacity with the least likely impact on energy costs (although there will be some of course) and the least costly installtion v/s installing a larger tank, or whole house gas tankless conversion.

When the new energy standards hit next year and you can no longer get 80 gallon electric tanks, expect to see a lot of these superchargers going in. They are going to solve a lot of capacity problems for the least amount of money, space and energy.

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Ad by Plbg.com:

Seisco tankless available at:

[www.plumbingsupply.com]



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Scott...Have you seen this Supercharger in action? When I ran the numbers at, just shy of 31000 btus, it didn't look good.

YES! Put one in a friends house. He was running out of hot water with a 50 gallon electric tank. 4 morning showers back to back was leaving him getting the cold one and no gas for a Rinnai Conversion. Now no problem!

Remember it is only having to raise the water temperature a few degrees to keep the hot water going until the peak load stops. It does not take that many BTUH/KW to do that job.

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