I need to replace my 50 Gal. gas water heater.
I've been living alone in a house and never run out of hot water. I
always take showers, never baths, and my overall hot water use is
I'm wondering about two things.
Would a 40 Gal. tank meet my needs and would I realize a noticeable
savings by going with a smaller tank?
BTW, I rent the tank.
You mean by a 40 gallon gas heater? Or a 40 gallon electric heater?
If comparing electric versus gas do a cost comparison of the two
fuels, for your area.
As long as it provides sufficient hot water each time you use it is
doubtful that you would save very much, if anything noticeabl;e by
installing a smaller tank.
the amount of heat lost from a well insulated tank/heater being very
Also the heat 'lost' from the heater helps, in winter anyway, to warm
Note. The difference in surface area of a 40 gallon compared to a 50
gallon tank will be approx. of the order of 22% (very roughly). So the
slight difference in loss of heat from the hot water inside a well
insulated tank to the ambient air temperature of whatever room in
which it is installed will be very slight!
My electric company says that my hot water costs, typically, less
than 20% of my total electricity bill. In my case as a single person
less than that. So even if that could be reduced by one quarter the
reduction in cost each month would hardly be significant. maybe 30
cents per day; at best?
most folks used 20 galon heaters decades back no problem. even with
if you are in a cheap electric area. pacific northwest, an instaneous
water heater will save you a lot
I can get by with a 5 gal heater in my motor home ,, 40 is gross
Probably. I just checked and we have a 40G gas unit. House of 3. We do
have to time our showers/tub baths a bit but it is not hard. The dishwasher
has to be accomodated for as well. Nominally need about 20 mins between
40G is plenty for one person. Ok for 3 with a little timing.
Yes, and you are right. It's an older unit and was not maintained at *all*
by the renters. I am pretty sure we are getting about 50% efficency out if
I dont expect anyone to really 'track' all any of our posts to add things up
so I'll add I'm the one who was in Japan almost 7 years with house rented.
I am pretty sure this unit was replaced while we were gone, about 6 years
ago? I bet it has a coil problem of some sort.
We have to unpack the last of the boxes in the garage before we can just
drain it and see what's up. Having only just repaired the 'sunroom' we have
not yet repopulated all the stuff stored in the garage so this isnt an
option to just drain it.
It is very possible the unit is about 7 years old now with zero maintenance.
With regular maintenance, they nominally last 15 years. Not sure what you
can expect with none at all though?
It is not impossible to think we might be getting about the efficency of a
20G unit just now? I only can see it is a 40G and a long shower (over 10
mins) means a reheat time of about 20.
FWIW, we had a 40 gallon for our family of four in our old house and we
never ran out of hot water. Showers, laundry, dishwasher, it kept up with
The savings to be had are the difference it takes in gas to keep 50 gallon
versus 40 gallons at temperature. This is a direct ratio of the heat loss
of the two tanks as the larger tank has more surface area. In either case,
if you use 10 gallons of hot water it will be replaced by 10 gallons of cold
water and on either sized tank it will cost the same to bring it up to
If you heat your house in the winter there will be no savings. The heat
lost from the water through the tank and into the air is just the same as
the heat from your furnace or boiler that would have to run longer, so, your
savings may take place only half the year or so.
I'd replace it with the easiest solution. If the connections of the 50
gallon tank line up, it is an easy swap. If, however, you'd have to re-plumb
for the smaller tank, you'd probably wipe out a year or two in savings.
I was just thinking that a 50 gallon tank that needs to be kept at a
certain hot temperature would require more gas than a 40 gallon tank.
I don't know how the tanks work, but I was assuming that the tank's
complete contents are kept at a fixed temperature.
Yes, they are. The greater the mass the more heat to be stored and the more
heat given off during the down times. What you need to know is how often
and how long the burner runs just to maintain the heat level. As I said, if
that "lost" heat from the tank is helping to heat your house, there is no
additional cost during heating season.
If you do downsize, under your circumstances even a 30 gallon would be OK.
That is really a lot of hot water for showers or even a batch of laundry,
especially since most can be done in cold water these days.
As pointed out the cost of the slightly less heat leaking from the
surface area of a 40 gallon tank as compared to that leaking from the
surface pf a 50 gallon tank would be minimal.
Also that heat, if you heat your house during say the winter or longer
(depending where you live) merely means that your furnace or other
heating devices would operate slightly longer to make up for the heat
'not' coming from the hot water tank.
Personally thinking the the difference will be so slight that the most
economical plan is just to slap in another heater with exactly the
same dimensions and plumbing hook-ups.
Also as pointed out the cost of hot water is not, usually, one of the
major ongoing household costs. Unless you consider that cost of gas
will increase drastically?
Intensive discussion about the difference in cost of the amount of
heat leaking (into the house itself) from keeping the difference of 10
gallons of hot water at a certain temperature seem rather pointless.
Presumably the water heater/tank is insulated???
What we do is leave warm shower water and the occasional hot bath to
cool down warming the air etc. in the bath room before drainuing it
away. Of course because of moisture we run the bathroom fan while
doing that which 'wastes' some warmed air to outside.
If you are really agonising about the overall cost of hot water and
your hot water use is low; look at the cost of electricity versus gas
in your area and the costs of installing a cheaper and smaller
electric hot water heater. There will also be plumbing costs if you
can't do it yourself. And then get rid of the gas connection, chimney
or flue vent completely.
This discussion is getting far too complicated.
Why rent, buy it its cheaper in the long run, you will save with a
smaller tank. You will also save because the new tank wont have scale
at the bottom. To save more shop and compare by EF energy factor, alot
of cheap ones are still 50 EF
Well had I known I would be still be in the same house ten years ago,
I would have bought a tank then.
If I buy a new tank now and move in a couple of years I think I would
lose out on the deal. A move is a distinct possibility for me in the
next few years.
Check out the following:
It's a rather indirect but valid way of guesstimating the annual savings
a 1 person household would see in replacing an old water heater with a
40 gal vs a 50 gal.
So, assuming that the 40 and 50 gal heaters are equally efficient and
adequate to your needs, you should save approx 20 therms per year with
the 40 gal. Where I live, gas is running between $1.25 and $1.50 per
therm, so that would be a $25 to $30 savings per year.
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