# Forum Home Renovation Plumbing  How long will a 9kg gas bottle last for a cooktop?

## Daren

Anyone using 2 x 9kg gas bottles and just refilling them yourself? 
I have to get gas installed (only for cooktop) and Im thinking of going this route. That way you're not paying for rental on the cylinders. 
Just wondering how long they last before filling up. Or should I just get one of those big buggers.?? 
thoughts, opinions advice?  :Smilie:

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## wonderplumb

OK, A 9kg bottle of gas x 49.9mj of heating energy p/kg will give you a theoretical 449.1mj worth of heating energy to use. 
This doesnt take into consideration any temperature variation factors and wouldnt seem relevant with you being situated in QLD as the gas boils and vapourises at different rates depending on ambient temperature.
So we take your 449.1mj and times it by your two bottles to give you 898.2mj.
Your cooktop should have a mj/h rating on it so for now we'll work on an average of 40mj/h for a 4 burner cooktop.
So 898.2mj divided by 40mj/h should theoretically give you 22.455hrs of continuous cooking.
However, being in QLD you will more than likely get butane rather than propane as it has a higher boiling temp. and isnt suited to colder climates so it then becomes,
9x49.2= 442.8mj  times your 2 bottles = 885.6 divided by 40 = 22.14hrs which is bugger all difference really. 
 As for choice of supply it depends on cost, here it costs me near enough to $30 for a 9kg refill at the servo but I get a 45kg bottle exchanged for $95 delivered and that does us all winter with a room heater.
Work out the price of your gas per kg doing it either way and from there you can calculate price per megajoule or per hour using the above figures which will ultimately make the decision for you. Hope it helps.

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## Vernonv

Hi Wonderplumb,
That's a very informative calculation.    

> Your cooktop should have a mj/h rating on it so for now we'll work on an average of 40mj/h for a 4 burner cooktop.

  I just have a question regarding the consumption - is the assumed 40mj/hr the maximum consumption if ALL burners were always used? So in theory if you only used 1 burner at a time you would get over 80 hours, 2 burners = over 40 hours, etc.

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## wonderplumb

Aaah, well spotted vern, I did mean to say that the mj/h rating is calculated with all burners going. So at 22 or so hrs of cooking is with the thing running flat out, but if say your having a roast each night and only boiling a pot of greens or spuds for mash this time is greatly increased.

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## Bros

> Anyone using 2 x 9kg gas bottles and just refilling them yourself? 
> I have to get gas installed (only for cooktop) and Im thinking of going this route. That way you're not paying for rental on the cylinders.

  I have a big bottle just for cooktop and it lasts a couple of years. I wouldn't go down that road again as if you run out you are out with no warning. 
A mate has the same set up you are contemplating.

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## dazzler

Hi 
we had two swap and go's at our last place and was very surprised how long they lasted.  Seemed like a couple of months between refills and having the second one meant you could swap it when it suited you! 
Highly recommended.

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## Smurf

I've got the same setup, 2 x 9kg gas bottles which run the cooktop only on a dual fuel stove (electric oven and gas cooktop in the one unit). 
I live by myself and am pretty conscious to not waste energy. I wouldn't call myself a green, but I can't see the point in wasting resources especially with the carbon issue etc. So I cook with the lids on pans, don't boil more water than I need etc. But on the other hand I never eat take aways so the cooktop is used most days. 
I moved in 6th of January 2008, just over a year ago, and the first bottle is still going fine. So at about $33 to swap that's pretty economical I think. 
When I had it installed (as soon as I bought the house - the previous cooker was broken), the gas fitter said it should be about 3 months for an average family. I've got 12 months so far, but there's only one of me and I do try to be economical. 
At a previous address I had a gas room heater in an open plan house. 2 x 45kg gas bottles and went through about 10 of them each year and that was despite insulation and not being wasteful. At $114 each last time I checked, I wouldn't recommed that option unless you're in a climate that doesn't need too much heating.  
It's a bit too expensive here in Tassie - and electricity works out at the equivalent of a bit under $70 per cylinder so that's certainly a cheaper option. Use a heat pump and it will be the equivalent of $20 - $25 so that's massively cheaper. Wood at $100 per tonne used in a combustion heater (not an open fire) works out about the same as the heat pump. That will vary in different locations - LPG might be cheaper than electricity in some places so check locally if you want to be sure. 
Overall I'd say LPG is economical for cooking and it's better than electricity in terms of how it works - temperature adjustability when cooking etc. But it's too expensive for heating if you use the heater a lot.  
I'm not sure if the gas supplied here is butane or propane but I'm guessing it's propane given that we get temperatures below zero in Winter. 
Natural gas is generally a lot cheaper than LPG. Worthwhile if you're using gas for heating etc but for just a cooktop I'd get the 2 x 9kg cylinders if it's just for normal household use. :Smilie:

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## Honorary Bloke

Wonderplumb, 
Have a Greenie!  Above and beyond. . . . :2thumbsup:

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## phillta

Is there any way of measuring how much gas is left in the bottle? I'm dreading mine running out before the snags are done.

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## SilentButDeadly

You can get simple LPG bottle stickers that are temperature sensitive and will show you where the gas level is OR you can put a pressure dial gauge on it. 
We use the big 45kg bottles and we don't pay rental for the bottles......'just' the $98 every time I replace the bottle.   
Since switching over to gas boosted solar hot water, gas consumption has fallen into a hole.  The gas boost to the solar has been off since October and will likely remain that way until the end of March.  Only the stove is using LPG and I expect that bottle to last another 12 months as it was near full when it was switched over at the end of August last year.

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## wonderplumb

An easy way to check a 9kg bottle is to tip a 10L bucket of hot water over it while its running. Run your hands over it from top to bootom and you will find that the bottle will be hot untill you get to where the level of the LPG is where it will be much colder. The difference is very noticeable, you'll be suprised.

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## Gooner

I think Wonderplumbs comprehensive response deserves some reputation points from Daren  :Smilie:

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## Daren

Sure, why not. How do I do that? 
Thanks to everyone for your replies.  :2thumbsup:

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## Gooner

bottom left hand corner on each persons posts under their name, location etc. You will see the middle icon of the balance scales. Click on it.

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## Daren

done  :Peace2:

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## Smurf

My first gas bottle ran out a couple of weeks ago. 12 months of use on one 9kg bottle but that's only for one person.

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## WillyInBris

Thanks Smurf and guys most informative. 
The wife decided to go window shopping today for the new house and decided she wanted a big ass cooker no real problems with that on my part she bitches her ass of that all ovens are to bloody small to work with and she wants a gas cooktop (I guess thats what you get for marrying an ex Chef, Gorden Ramsey has nothing on her when things are going pear shaped in the kitchen). 
We have plenty of room for it so no real problems and she has money set aside for it but what are we talking about saving when it comes to a 45kg bottle vs the 9kg bottles. 
For  a 9kg refill I pay $20 at BCF for a refil for the BBQ so how much more does it cost for a 45 I guess you need to pay rental as well but it couldn't be that much more could it over a year or is it? 
5 x 9kg =$100  
Anyone got any idea on the costs of 45s in regional areas I am guessing you have to pay for a hire as well? 
Willy

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## WillyInBris

Ok So I thought I would just add the following I spoke to Elgas and was quoted the following I couldn't imagine Country Energy being and less. 
45kgs $103 prepaid order $98 
Service fee annual charge $44 for 1 cyl or $66 for 2 if your going to put a heater on etc 
One thing I wanted to ask people are the 9kg bottles put outside as well that some of you are using, I am thinking so because of safety issues probably a stupid question but just though I would ask.

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## Smurf

> One thing I wanted to ask people are the 9kg bottles put outside as well that some of you are using, I am thinking so because of safety issues probably a stupid question but just though I would ask.

  I have two 9kg bottles outside. They are sitting on the ground next to the house quite some distance from the kitchen (they are out of the way where they are located). 
They are both connected to the regulator, you just turn the knob on the regulator to select which bottle is used. All the plumbing from the bottles to the regulator and then into the kitchen is in copper.

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## Bloss

Just me, but the thread title makes me smile every time I see it as I think of the answer 'depends how much you use!"  :Biggrin:   
Would be having the bottles inside, but have a number of friends who have bush and coast blocks who have found a problem getting any of the gas bottle companies to deliver and so use the 9kg bottles (filled to 8.5kg by Bunnies for some reason!) without problems. A couple have had twin copper pipes run in by their plumber with  two-way-off tap so that they can swap over when one runs out without going outside. 
If you had to use a bottle inside then a GasFuse http://www.gasfuse.com/index.htm  would be a must - but as you need to be able to depress the device while lighting that would need to be adjacent to the stove or other gas device.  :2thumbsup:

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## ThornyBob

G'day,   

> Hi 
> we had two swap and go's at our last place and was very surprised how long they lasted.......

  you did well, our experience with these bottles has been dismal. They almost always refuse to supply gas when you need it !!  We have two bottles, one of theirs and one of our own, ours always goes right to end no problems. 
I've got no idea what the problem is, the bottles all look the same except ours is "nicer" and the tap always works properly.... 
Maybe it's the gas in the swap 'n goes ? does it freeze up and block the outlet ? water in the mix ? 
cheers,
Bob

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## Black Cat

No idea what you could be doing Bob. I have been using swap and go nine kilo gas bottles for the last two and a half years. In the caravan I was getting through one bottle every couple of months as I was using it to heat water, as well as cook, and boiling the kettle for drinks etc. Now I am inside the house I am still using the partly finished bottle I took off the caravan when I moved out over a year ago. Still waiting for that sad little flicker and stinkie death scene. This is after making litres of jam as well as cooking for myself (alone) all that time. I tend to cook up a storm, so no chances of it being underused. 
No problems with freezing, leakgin, blocking or similar. All sweet. I would get a gas technician to have a look at the lines if I were you.

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## Smurf

Sounds like something is wrong with the lines, regulator etc as I've never had a problem like that with ANY gas bottle (and between home and work I've used quite a bit of LPG over the past 20 or so years). I'd get a plumber or gas fitter to have a look - better safe than sorry when dealing with gas or electricity in my opinion.

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## ThornyBob

G'day, 
didn't ignore you, just found the subscription default  :Redface:  
Only bottle problems we have are with the swap 'n go [or their mates], our own bottle runs right to empty without any problems - all on the same BBQ. 
Damn weird, drives me nuts, and it's gonna get worse cos I reckon that in the future either we won't be allowed to have our own bottles or it will get to the stage that the suppliers will decide that personal bottles are not worth the hassle and will only stock swappers. 
cheers,
Bob

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