Post by Donna Ohl Post by ransley
98% water heaters are common even 96% boilers
I think the reason for this is somewhat misleading.
If I understand this correctly, almost all the heat energy put into an
electric heater gets put into the water. Basically, the water cools the
heater coils down by taking the heat off the heater coil.
In the case of a gas water heater, the water cools down the flame by taking
heat off the flame (figuratively speaking) but a LOT of heat goes up the
They baffle the flue to slow down the rising air but they have to let the
hot air out. If they cooled the hot air to room temperature, it wouldn't
rise and get out of the house and that would be a bad thing from the
standpoint of carbon monoxide poisoning.
So, I think the fact that all none of the heat energy that went into the
electric coils goes up any flue - it's all absorbed by the water - is what
makes the electric water heater 98% efficiency.
But, as someone stated, I suspect the power generation is about 70%
efficiency, so, the true efficiency of electric water heating must be
vastly lower than 98% taking distribution into account.
But, how can we account for that true efficiency?
Electric are all 100% efficent, all energy consumed is used to heat
water, and energy factor should be near 100 as well with great
insulation. Almost all gas water heaters burners are about 80-83%
efficent, but an additional 17-20% goes up the chimney 24 hrs a day,
Energy Factor ratings account for loss up the center uninsulated flue
part of the tank and reflect overall efficency, which for most gas
tank is 50-60 with one I saw of 70. Condensing gas water heaters,
Boilers, furnaces, are different, have a second exchanger that lowers
flue temp to near room temp and are forced out the flue by a fan. A
condensing 93% water heater wont loose 20% in flue loss since the fan
stopped some of the heat loss, but even the best condensing tank water
heater of 93% may only be 83% Energy Factor [I guess]. Condensing tank
water heaters are really commercial units costing thousands. AO Smith
has them, I own one a 175000 btu unit, a Cyclone. For most, electrics
are and always will be more expensive to run unless you have a cheaper
Hydro Dam nearby, since for most oil- gas products generate
electricity. Someone stated 70% for electric, that is not true to you
for what you consume and pay, he was talking about transmission line
loss, for you electric tank is 100% efficient, but here electricity is
still 30% more than NG. If nobody in your neighboorhood has an
electric furnace then you can bet Ng is still cheaper per Btu. Now in
the last 6 months all petroleum products are going up fast, but
electric will follow in the long run.