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Cost to run 40 vs 50 gallon Gas Hot Water Tank?

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  • Mar 8th, 2013 2:41 pm
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Sr. Member
Aug 11, 2008
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Cost to run 40 vs 50 gallon Gas Hot Water Tank?

Our hot water tank was replaced this morning because it was leaking. It was 16 years old. They were supposed to install a 50 gallon tank, but they messed up and installed a 40 gallon instead.

Info:

- There are only two of us in the house, but we have guests twice a month or so
- The tank is a basic vent-to-the-chimney gas hot water heater
- The cost difference to rent a 50 gallon over a 40 gallon is negligible
- We aren't planning on staying in the house long enough to make purchasing one cost effective (our rental cost is going up to $12.50 next month)
- One bathroom, but we will be converting the powder room into a full bathroom in the next year

We could barely get two showers out of our old 40 gallon tank, so I want them to install the 50 gallon they were supposed to install. However, they argued the following:

a) It costs less to run a 40 gallon tank
b) The old one was probably filled with sediment so we got very little hot water

Is there any truth to either of these? Is there a noticeable difference in the cost to run a 40 vs. 50 gallon tank?
16 replies
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Oct 6, 2010
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inmyturret wrote:
Mar 5th, 2013 3:28 pm
Our hot water tank was replaced this morning because it was leaking. It was 16 years old. They were supposed to install a 50 gallon tank, but they messed up and installed a 40 gallon instead.

Info:

- There are only two of us in the house, but we have guests twice a month or so
- The tank is a basic vent-to-the-chimney gas hot water heater
- The cost difference to rent a 50 gallon over a 40 gallon is negligible
- We aren't planning on staying in the house long enough to make purchasing one cost effective (our rental cost is going up to $12.50 next month)
- One bathroom, but we will be converting the powder room into a full bathroom in the next year

We could barely get two showers out of our old 40 gallon tank, so I want them to install the 50 gallon they were supposed to install. However, they argued the following:

a) It costs less to run a 40 gallon tank
b) The old one was probably filled with sediment so we got very little hot water

Is there any truth to either of these? Is there a noticeable difference in the cost to run a 40 vs. 50 gallon tank?
Seems like you already answered your own question with your info section, 'The cost difference to rent a 50 gallon over a 40 gallon is negligible', I would say you wouldn't notice the cost difference. The stickers on the tank should tell you. Then look up a 50G to compare. Confused though. You are not planning on staying because of a $12.50 a month increase, but you are reno-ing a powder room into a bath? If you are renting the house, I'm confused as to why you are dealing with the tank and doing a reno IF you don't plan on living there much longer.
t3359 wrote:
May 13th, 2016 9:56 am
...The magic eight ball would randomly say things and logic would never work. The eight ball is just a gimmick and a waste of time and effort. So equivalently, there is no possibility to "debate" you.
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Apr 4, 2009
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A 40 gallon tank cannot provide enough hot water for two showers ??? !!!!

May I ask how long these showers last? 1 hour (or more)?

40 gallons is a LOT of hot water for a household of two.

Normally, over a life of a tank, we do not expect 10% of the tank to accumlate sediment. So, I am thinking there was something very wrong with OP's orginal tank to begin with.

How big is OP's house. If it is ment for a family of four, then a 50 gallon tank may be warranted - for the next family. But for 2 people, 40 gallons is plenty.
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Mar 8, 2002
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We use less than 1 cubic meter of natural gas a day for our 50 US gallon hot water heater, which costs about 23 cents a day. Pretty good deal for hot water if you ask me. If a 40 gallon uses any less, it will be pennies a day and maybe amount to $10 a year.

The volume of the tank is not the important spec, you need to look at recovery rate - how fast the heater can heat up cold water coming in as hot water is being consumed. This will be a bigger help to "not running out of hot water"
[OP]
Sr. Member
Aug 11, 2008
630 posts
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koffey wrote:
Mar 5th, 2013 3:48 pm
Seems like you already answered your own question with your info section, 'The cost difference to rent a 50 gallon over a 40 gallon is negligible', I would say you wouldn't notice the cost difference. The stickers on the tank should tell you. Then look up a 50G to compare. Confused though. You are not planning on staying because of a $12.50 a month increase, but you are reno-ing a powder room into a bath? If you are renting the house, I'm confused as to why you are dealing with the tank and doing a reno IF you don't plan on living there much longer.
Our total cost to rent the hot water heater is $12.50/month. We do not plan to be in the house long enough (max 5 years) to make purchasing a hot water heater cost effective (I only brought this up so I wouldn't just be told to buy one). The house is currently a 4 bedroom with 1.5 bathrooms. We plan to reno it to a 2 bathroom before selling since based on comparables in our neighbourhood, we will more than make our money back. We bought it as a fixer-upper. We had no choice but to deal with the tank, since it was leaking.

I am more questioning the cost to operate the tank, since the difference in the cost to rent is negligible. It if will actually save me money, then I won't make them come back. If they cost the same to operate, I will make them come back and put in the 50 gallon.
Busybuyer888 wrote:
Mar 5th, 2013 3:52 pm
A 40 gallon tank cannot provide enough hot water for two showers ??? !!!!

May I ask how long these showers last? 1 hour (or more)?

40 gallons is a LOT of hot water for a household of two.

Normally, over a life of a tank, we do not expect 10% of the tank to accumlate sediment. So, I am thinking there was something very wrong with OP's orginal tank to begin with.

How big is OP's house. If it is ment for a family of four, then a 50 gallon tank may be warranted - for the next family. But for 2 people, 40 gallons is plenty.
Two showers for a total of about 30 minutes. The third person would have to wait for hot water. I agree that there was probably something wrong with the tank, it was 16 years old after all! I'll try out the 40 gallon for a week or two. If I can't get at least three consecutive showers out of it, we will make them replace it.
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inmyturret wrote:
Mar 5th, 2013 4:14 pm
Our total cost to rent the hot water heater is $12.50/month. We do not plan to be in the house long enough (max 5 years) to make purchasing a hot water heater cost effective (I only brought this up so I wouldn't just be told to buy one). The house is currently a 4 bedroom with 1.5 bathrooms. We plan to reno it to a 2 bathroom before selling since based on comparables in our neighbourhood, we will more than make our money back. We bought it as a fixer-upper. We had no choice but to deal with the tank, since it was leaking.

I am more questioning the cost to operate the tank, since the difference in the cost to rent is negligible. It if will actually save me money, then I won't make them come back. If they cost the same to operate, I will make them come back and put in the 50 gallon.



Two showers for a total of about 30 minutes. The third person would have to wait for hot water. I agree that there was probably something wrong with the tank, it was 16 years old after all! I'll try out the 40 gallon for a week or two. If I can't get at least three consecutive showers out of it, we will make them replace it.
Gotcha. Again, the savings are going to be minimal, but look at the sticker on your tank, google a 50g of the same brand, ect... Should tell you.
t3359 wrote:
May 13th, 2016 9:56 am
...The magic eight ball would randomly say things and logic would never work. The eight ball is just a gimmick and a waste of time and effort. So equivalently, there is no possibility to "debate" you.
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OP should also ensure the showers have low flow shower heads, to help minimize water usage. Old shower heads could end up wasting a lot of water.
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You should see not difference at all. The cost of the hot water is really based on what you use, whether it is an 40 or 50 gallon storage tank. If you drain the tank regularily, well yes, you may see something but even then, it will be minimal as you cannot isolate your hot water tank from any other gas appliance.
As for getting enough hot water out of a 40 gallon tank, we raised 2 kids with a 40 gallon tank, no problems at all.
It’s not how far you fall that counts. It’s how high you bounce that counts! General G Patton
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Pete_Coach wrote:
Mar 6th, 2013 7:19 am
You should see not difference at all. The cost of the hot water is really based on what you use, whether it is an 40 or 50 gallon storage tank.
There is also a cost to lost energy while the heated water sits in your tank waiting to be used (standby loss). Surface area on a 50 gal tank would be about 15% more (assuming the tank diameter increases rather than the height) and I seem to recall hearing that up to 20% of water heating costs can be lost in standby so that would mean a 3% higher operating cost. Not much but there is a difference. (20% may be too high but at the result is small already it doesn't matter if that number is too high).

Recovery times are a function of the heating element in the unit. Larger units will often have larger heating element and therefore faster recovery times.

I agree with others that the performance of your previous unit was not what it should have been. A 40 gal tank should be sufficient for your needs. Especially with just one bathroom. A few handwashes in a powder room will not change that.
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Oct 22, 2007
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I agree that the cost difference to heat up to 40 vs 50 gallong tank is minimal that you probably won't notice it.

When we bought our home it had a 40 gallon tank, and it worked out well untill we had 2 kids, and eventually guests. When it came time to replace we went with the 50 gallon and on rare occasions we run out of hot water even though the tank is around 140 F which is quite high. The only time we run out is if showers are taken back to back. When we have guest stay over, then it's definately a problem, as well as when we fill up our soaker tub. In future, we'd probably upgrade to a larger tank only because future home owners may have more the 4 people in this home and we tend to run out on occasion as it stands now.

In your situation I don't think you'll have a problem, but I can't speak on behalf of future home owners. If it ain't broken.........................
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Nov 21, 2004
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They were supposed to install a 50 gallon and screwed up...and want you to live with their mistake.... Why would you do that?
Deal Guru
Mar 23, 2009
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40 is pretty limiting even for just two people IMO. In fact, a 50 (with sediment) couldn't even fill our soaker tub even once. Even if we didn't use the soaker tub, if we tried to use a second regular tub and a second person tried take a long shower, we would sometimes run out of hot water. Add in a washing machine and a dishwasher, and it's definitely a royal pain. This was seasonal though. We'd only run out of water in the dead of winter. In the summer it was fine, presumably because not as much hot water is needed to mix with the cold. Cold water in the winter is colder for obvious reasons.

They should install the promised 50 gallon tank. Hell, I wanted to install a 75, but they said it wouldn't fit in the space, so I installed a tankless instead.
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Aug 27, 2009
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JWL wrote:
Mar 6th, 2013 8:20 am
There is also a cost to lost energy while the heated water sits in your tank waiting to be used (standby loss). Surface area on a 50 gal tank would be about 15% more (assuming the tank diameter increases rather than the height) and I seem to recall hearing that up to 20% of water heating costs can be lost in standby so that would mean a 3% higher operating cost. Not much but there is a difference. (20% may be too high but at the result is small already it doesn't matter if that number is too high).
The typical heat loss from a tank WH is about 30W so the additional heat loss of a larger WH is pretty inconsequential.
Plus that heat loss goes into your home from Sept. to May so that heat isn't really lost though it is produced at a typically lower efficiency than your furnace.

My actual cost of gas used for water heating is less than $10/month for a family of four including 2 teenage girls, 3% of that is $0.30.
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Sep 16, 2008
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I hate low flow shower heads...show me the pressure!!!! LOL :)
Busybuyer888 wrote:
Mar 5th, 2013 10:40 pm
OP should also ensure the showers have low flow shower heads, to help minimize water usage. Old shower heads could end up wasting a lot of water.
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aple wrote:
Mar 7th, 2013 2:34 pm
I hate low flow shower heads...show me the pressure!!!! LOL :)
Pressure is the same, just the amount of water is altered. The design of the head is important and most designs you would not even know it was low flow.
It’s not how far you fall that counts. It’s how high you bounce that counts! General G Patton
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