That "savings" would equate to 300 Kwh per month. I simply cannot imagine saving more than 20% of usage due to standby losses on a well insulated tank. Therefore, for that level of savings, you'd need to be using 1500 Kwh just to heat hot water. I find that simply unbelievable.

My usage is reduced because I'm the only one in the house and the washer and dryer only run one load per week. Furthermore, the stove and the dryer both run on natural gas.

My perception is that the heating element is more efficient. My old water heater was a GE Smartwater that was stupidly inefficient. The demand heater is a Bosch AE125. In addition to replacing the main water heater, I put in an undersink unit (AE7.2) under the kitchen sink. The sink was the longest run of pipe in the house (~35' of 1/2" pipe, which has been abandoned and removed). The main demand heater is near to 12' feet closer to the bathroom and laundry. I will look up the efficiency rating of the old water heater tomorrow. The Bosch is ~95% Just a side note, the wiring for the Bosch consists of 3 runs of 3 conductor 6 ga copper, vs. 1 run of 3 conductor 10ga wire for the tank

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

I fail to grasp the "efficiency" of an electric water heater. If the energy doesn't go into heating the water.........where does it go? There's no chimney to send waste heat as would be the situation with a gas water heater.

These units simply expend Kwh and provide BTU's.........nothing more.

Some units expend more kWh for the same BTU's therefore more efficient?

Just grabbed a snipit from Oregon Dept of Energy describing their tax incentives for efficient water heater installation.

"Qualifying tankless water heaters must have a minimum energy efficiency rating of 80 percent....."

That, coupled with the stated efficiency of the Bosch at 95%, seems to indicate a variable degree of efficiency

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

Again.......where does the lost energy go? Most lost energy winds up as heat somewhere........but in an electric heater, it usually ends up in the water.

The insulation on a tank water heater is not 100% efficient. Loss there.
The pipes connected to the heater - loss there, even when no demand, which is most of the time.
The water itself, into the pipes, and out.
Up the copper wires.

Love my Rheem tankless. The electric comapny does not.

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport

I'm sure it ends up as heat, just maybe not as much heat?
Maybe the heat is not transferred as well. I agree that on the surface (which is about as far as my knowledge goes) it would seem that all electric heaters should be equally efficient. Are there different materials that the elements are made out of? My last water heater has the energy guide sticker on the side with the scale of energy usage, that upon examination showed the usage for that model to be off the scale (thanks home depot)

Maybe it is just the heat escaping from the stored water.

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

The insulation on the tank is not related to the efficiency of the heater........AFAIK.

The pipes that are connected to the heater are the same........whether tank or tankless........unless you're using a separate tankless at each outlet.

I cannot fathom where you fellows are getting the savings.........unless you replaced a giant inefficient tank.

That's my take. Anything else is a discussion of losses........not efficiency. The losses that occur with a tank are well documented........but, they don't affect the efficiency of the energy use.

Back to the original subject, pressure.

You can put 2 pressure tanks in, might be easier for space or ??

We are on a community well, things were terrible, if I was in the shower I could tell if the neighbor flushed SERIOUSLY.

OK I put in a pressure tank 45 or 60 gallon, made things much better.
When I remodeled the basement the area above the existing tank was pretty much useless because of the plumbing running through it.
So I changed the plumbing a bit, and added a second tank.

Well the county has tweaked the system, and found the cause of our problem (badly kinked 2 " copper pipe).
But now you can take a shower and if someone flushes the toilet in our house you don't even notice it.

__________________
KLK, MCSE

1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.

I have one already, and my mom's house has one that doesn't get used anymore. Free is my kind of price.

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif