Is gas hot water cheaper per unit than a standard HWC?

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mudguard

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#3455621 24-Jan-2026 13:51

Bowie:

Wouldn't gas bottles would be cheaper than gas main from the street?

To be fair I've never looked into it. Plus I don't know how easy it is to setup a bottle connection vs the mains.

Scott3

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#3455659 24-Jan-2026 19:02

Bowie:

Wouldn't gas bottles would be cheaper than gas main from the street?

If you go the solar power way.

You would only benefit if you were home during the day to use the free power. Getting batteries for storage would be very costly so I am told from the neighbor's who have solar.

It depends how much gas you use.

Street gas (natural gas) is cheaper per unit energy, but the daily costs of being connected are now around the $2 mark.

LPG (bottle gas) is more expensive per unit energy (and even more expensive than low user power in many area's), but the daily cost of renting the bottles is much lower.

Note that the gas composition is different, so injector size changes are often needed to swap between the two gases.

If one is solely running a cooktop, LPG is likely the way to go (and if you are a low user, like a batch, it may even be cost effective to run 9 kG BBQ cylinders, rather paying rental on 45kg bottles).

But if you are running other stuff like hot water on natural gas, you will need to run an evaluation.

Natural gas is a little safer than LPG (lighter than air vs heavier than air). And having it piped in from the street means no need to occupy space for bottles, or need to turn on the second bottle and order a replacement when one goes empty (and the water in your shower goes cold).

LPG has the advantage of being stored on site. As part of disaster planning, one should not count on the piped gas network functioning, but somebody running the typical 2x 45kg LPG bottle setup, and who orders a new bottle as soon as one is empty, will have at least a few weeks LPG on hand. (make sure you have a manual means to light your cooktop as the electric lighter won't work without power).

gzt

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#3455671 24-Jan-2026 19:45

Bowie: Wouldn't gas bottles would be cheaper than gas main from the street?

You'll be paying for delivery, and most likely bottle rental (unless you want to pay for and lug man size cylinders to the filler at regular intervals. If you live next door to the station you could do it on a hand truck. Otherwise, forget it.)

gzt

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#3455673 24-Jan-2026 19:55

Genesis bill in my area is $175 per 45kg LPG bottle delivered (inc)
+ $6.75 rental per bottle/month. It's unclear to me if the price varies by region.
--
Coincidentally - our gas is used only for the shower and hot tap now. The dishwasher and washing machine use their built in electric heating. Consumption dropped after I switched the washing machine to 100% use it's internal heater. Nos I'm thinking I can change to 9kg swappabottles and eliminate the 45kg rental. I've been running a 6lpm shower head for a few years. I intend to drop that to a 5lpm when convenient.

AklBen

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#3455712 25-Jan-2026 08:44

gzt: Genesis bill in my area is $175 per 45kg LPG bottle delivered (inc)
+ $6.75 rental per bottle/month. It's unclear to me if the price varies by region.
--
Coincidentally - our gas is used only for the shower and hot tap now. The dishwasher and washing machine use their built in electric heating. Consumption dropped after I switched the washing machine to 100% use it's internal heater. Nos I'm thinking I can change to 9kg swappabottles and eliminate the 45kg rental. I've been running a 6lpm shower head for a few years. I intend to drop that to a 5lpm when convenient.

Don't you get pressure issues with 9kg bottles?

Kickinbac

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#3455726 25-Jan-2026 10:42

AklBen:

gzt: Genesis bill in my area is $175 per 45kg LPG bottle delivered (inc)
+ $6.75 rental per bottle/month. It's unclear to me if the price varies by region.
--
Coincidentally - our gas is used only for the shower and hot tap now. The dishwasher and washing machine use their built in electric heating. Consumption dropped after I switched the washing machine to 100% use it's internal heater. Nos I'm thinking I can change to 9kg swappabottles and eliminate the 45kg rental. I've been running a 6lpm shower head for a few years. I intend to drop that to a 5lpm when convenient.

Don't you get pressure issues with 9kg bottles?

You can do. The amount of gas drawn from the gas bottle to fuel your gas appliances must be matched by the vaporisation rate. Better explained here: https://www.elgas.com.au/elgas-knowledge-hub/residential-lpg/9kg-gas-bottle-instead-45kg-gas-bottle-house/

I was at friends place and the only appliance they have is gas hob on two 45kg bottles. They’ve been there 2 years and never changed a bottle! In their case I’d change to a 9kg bottle.

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gzt

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#3455734 25-Jan-2026 11:14

AklBen: Don't you get pressure issues with 9kg bottles?

I've run on a 9kg for a week or two when we ran out the two 45kgs and forgot to reorder. I didn't notice any problems, several times. I seem to recall I asked the gas company before doing it. The delivery guy has never commented on it just unplugs the 9kg and plugs in the 45kgs. Back when we had a gas hob. (now replaced with induction).

You've got me thinking. The 9kg has always been at least half full. I'll try for a longer period and use a whole 9kg bottle before I let the 45kgs go. Just in case.

gzt

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#3455747 25-Jan-2026 11:42

Kickinbac: https://www.elgas.com.au/elgas-knowledge-hub/residential-lpg/9kg-gas-bottle-instead-45kg-gas-bottle-house/

That was a good read. My summary:

- gas hob/oven - potential increase in carbon monoxide from incomplete burning
- potential lower combustion temperature and lower heat output
- potential safety issues if 9kg bottle is not grounded
- potential intermittent functioning of water heating systems and appliances
- lower pressure at lower temperatures in winter = worse issues
- lower pressure gas flow when 9kg below 80% full

Also a warning that hanging a 9kg in the air from a short gas connection hose is a bad idea. My 9kg sits on top of the 45kg on the rare occasions when it's used.

Boiled down to general advice that Australian supplier says don't do it - but if you must then make sure your 9kg is over 80% full.

I'm reconsidering my plan. It sounds like it might be viable for short periods only, and only for people with zero indoor gas appliances.

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