But is there realy enough insulation on any tank, maybe 2" of foam for say R 12, but code for attics in my area is R35 and optimal is R60. Loss also continualy occurs through the water pipes, you are keeping water hot, there is alot of loss.
Based on the comparison for tank type electric and tankless electric where there was clearly little standby loss from the heated tank I'd say yes.
Newer heaters have little valves that are designed to limit heat loss to the pipes in standby. Certainly insulating the hot water pipes is still a good idea.
Pete C.
Model Energy Factor Cost to Operate* Annual Savings=B9 Annual Savings=B2
250SX/SXO 0.85 $250 $110 $151 125B/BS 0.69 $308 $52 $93 125HX 0.80 $266 $95 $135 125FX 0.78 $273 $88 $129 40-gallon tank 0.59 $361 75-gallon tank 0.53 $410Note the stated savings. In the winter the extra gas used helps heat your home If the heating season lasts 6 months then divide the savings by ONE HALF.
Now the largest savings bosch lists is $153 divide by 2 it saves about
76 bucks a year. Thats nice BUT the install costs several times the cost of a standard tank.Thats ridiculous that the extra gas heats a home with a tank, exactly the oposite will happen with an open flue to a chimney, its called draft. Savings, at what price a therm, certainly not what is charged now. Look hallerb you can run your numbers any way you wish to make yourself feel better you don`t own one, but I have proof of a 4yr payback, my utility bills. You need to talk to owners of Ng tankless.
The heat from the extra gas used mostly goes up the chimney, not into your home since it's mostly stack losses, not losses through the exterior of the heater. What heat does get out into your home may assist in heating it in the winter, but it also hurts when air conditioning in the summer.
Pete C.
You dont know what BTU yours is running at, unless theres a digital readout?
besides its largely of flow.
some folks are happy with a anemic shower and never have more than one hot water thing on at the same time.
whereas I like a nice strong shower and removed the flow restrictor from my wand shower.
I also occasionally have 2 washers and a dishwasher running at one time. although I avoid showeriung when anything else is on.
Our tank from november of 2000 is a Rudd 50 gallon 75,000 BTU unit. It was the largest tank that would fit the space.
with normal showering we never run out of hot water
Losses in pipes are NOT a part of the Bosch comparison. Yes, we must recognize them as they will extend our use of hot water while we wait for the pipe to heat back up (or we use a recirculation pump).
The Bosch comparision said that electric tankless was a infinite payback at 50 gallons and a near infinite payback at 80 gallons.
Yes, stack losses and insulation losses are the dominant factors in energy use difference between tank and tankless gas heaters. In this case, gas tankless makes a large enough difference to perhaps get a positive payback in 5-7 years.
Tank type Gas water heaters are not allowed, by building code, in many locations to be inside the heated/cooled space. Tankless can be, if combustion air is brought in.
So energy losses by a gas tank type water heater do not add to building heat, not always.
At the instant that the gas tankless fires, if it fires anything close to its max setting, and yours is not, will rival or exceed the gas demand of natural gas furnace.
Even at 30,000BTU input it consumes a large volume of gas in a very short interval. This gas use is smaller, and shorter in duration, than the gas use of a 40,000BTU gas tank type.
Yes, the efficiency of tankless is great!!!
You are clearly saving money. But $20/mo, $240 a year will take you several years to payback this investment.
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