The Hybrid Tankless Water Heater

A conventional water heater uses natural gas or propane to heat a tank of water that's typically 40 to 50 gallons in size. The drawback of this design is that the water heater is constantly keeping that water hot (so its ready when you need it), but doing so can cost you a lot of money. And if the first person in the shower spends 15 minutes there, everybody else is getting a cold shower... Yikes!

A tankless water heater is one that doesn't store any water. It only creates hot water when you need it, so its much more energy efficient and costs a fraction to operate. Plus your hot water is endless. Carbon Bigfoot says... Oh Yea!!

Now let's not confuse "tankless" with "instant" hot water. The amount of time it takes for you to get hot water to your fixtures is still going to depend on how far the hot water heater is from the fixture, regardless of whether it is conventional or tankless. An "instant" hot water heater is usually a small device under the sink. You'd need one of these next to every fixture if you wanted instant hot water everywhere. Your typical "tankless" hot water heater is a small box that mounts to the wall and replaces your old conventional water heater.

So why doesn't every new home have a tankless water heater. Well, there are some issues with them that many plumbers are not aware of and current tankless owners wont tell you about until you've already got yours installed and you're complaining about it.

The first issue is that they require a minimum flow rate to kick on the hot water. In short, you can't trickle hot water out of your faucet while you're washing your face or your dishes. The typical tankless water heater wants to see between .5 and 1 gallon per minute flowing before it will light up the flame. And everytime you turn on the hot water, their will be a delay as it waits to be sure that you've turned the faucet high enough. So you'll be getting hot water and turn the faucet off. Turn it back on and you'll get a blast of cold water again. Its infuriating if your trying to do dishes in the kitchen sink.

The second issue is that there is a lag time as they respond to changes in demand. So if you're in the shower and someone turns on hot water in the kitchen sink, you'll get a blast of cold water while the tankless is thinking about turning up the flame to supply the two fixtures. Your pissed-off wife is going to do this to you often because you installed that stupid tankless water heater. "Yes ma'm may I have another!"

But wait all is not lost. There is a solution. I call it the Hybrid Tankless Water Heater. Just add a small electric water heater, say 4 to 8 gallons, on the output of your tankless. I have the Bosch Aquastar 250SX-NG Tankless water heater and I've added the Bosch Ariston GL8 Ti electric water heater to its output. The tankless water heater uses it's gas flame to heat the water which then goes into the 8 gallon tank. This small tank is well insulated and uses only a small amount of electricity to keep the 8 gallons hot over night. The 8 gallon tank buffers out all the temperature fluctuations from the tankless and it is still highly efficient to run. It's the bomb!! And it's endless! You can spend every last penny that you saved on energy on your new expensive water bill. Give yourself a hand!

The 250SX and Ariston tank is enough to supply two fixtures at once, which means a its great for a 3 Bedroom, 2 Bath house like mine. The 250SX has been recently replaced by the 2400E, but I can't tell you anything about the newer model. I'd expect at least as good perfomance from the 2400E.

The final caveat is that the tankless water heaters have strict gas supply requirements as well as flue venting requirements. You'll need a new stainless steel flue and probably a dedicated 1" gas line to the water heater. Make sure your installer knows what they're doing!

I purchased my Aquastar 250 SX online at http://www.tanklesswater.com and the Ariston GL8 Ti from a local plumbing supply shop, though tanklesswater.com has the Ariston GL6 Plus which would also work fine. I had to get some extra flue segments because I couldn't mount it directly to an exterior wall. My cost was as follows:

• Bosch Aquastar 250SX-NG - $985.00
• 3" Stainless Steel Horizontal Vent Starter Kit - $229.00
• Extra Stainless Steel Flue Vent Pieces - $150.00
• Bosch Ariston GL8 Ti - $199.00
• TOTAL = $1563.00