Need some real numbers on replacing my Electric Water Heater with a Tankless system.

Bill Door’s comments got me thinking…

I’m an HVAC/Plumbing contractor and sell some gas tankless WHs. (Rinnai) I was told (and never questioned) that the average family would save $250-300 per year.

And I’ve been telling people that. In our industry (like many others) salesman play fast and loose with the facts. And so his comment made me wonder, “Have I been lying to people?”

Only later did I notice his example was for electric WHs, but I was already interested enough to find out if this applied to natural gas.

That bugged me enough to call Rheem’s engineers. **Now speaking about gas fired units only, ** they tell me that their energy efficiency ratings already take into consideration losses through the jacket. According to him, most tank WHs average 58-62% efficiency. We picked a model at random that had an efficiency rating of 61%. The [gas] tankless unit we chose had an efficiency of 84%.

So, my question to Bill Door, (or Una Persson et al) is this:

Given a reasonable set point, cost/therm and useage for a typical family of 4, what’s the average savings on a NG tankless vs a standard NG 40 gallon tank?

The Gas company said nothing was available, they verified and actually took their time.

As to propane, I just don’t want another delivered item. I already get oil for heating. I also don’t really want the tank outside, minor but enough to stick to the water heater and just buy a more efficient one in 4 or 5 years.

I will start looking into replacing the AC unit, it might be 15-17 years old at this point. I should see a substantial savings in replacing it.

Jim

BTW: Great questions the raindog. I hope we get a good answer.

I would say gas would have a much higher efficiency improvement than electric. Using either a point-of-use or tankless gas heater you only run the flame when actually using water, limiting one of the worst aspects of the gas fired system, the hot exhaust going up the flue. With an electric heater you only gain the amount of energy lost through the tank walls.