# Forum Home Renovation Heating & Cooling  Reverse Cycle Air Cond versus Gas Heating??

## martyjames

Hi All 
I was thinking of buying a natural gas unflued heater (i have a bayonet gas outlet) to heat my old federation house. I have a R/C air conditioner and assumed it would be expensive to use as a heater. However a friend said the R?C a/c would be cheaper to run than a gas heater. Is this right??? Also , i think this place will have big mould problems (the prev owner intimated as such)- would the rev a/c be a "dryer" heat?? ie better from the mould perspective?? 
thanks 
Marty

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## Smurf

Unflued gas heaters produce moisture in the air, reverse cycle A/C does not add moisture to the indoor air. A flued gas heater will also produce moisture but will send it outside where it's not an issue. 
So from a moisture perspective, a flued (not unflued) gas heater or reverse cycle A/C would be the way to go if dampness / condensation is a concern. 
As for running costs, it will depend on your local electricity and gas prices. For me here in Tasmania, reverse cycle A/C would certainly be a lot cheaper than gas. But in other locations the opposite is true. 
But a reverse cycle A/C will use about one third as much electricity as other electric heaters (for the same heat output) so it's certainly a better option than electric fan heaters, bar radiators etc. 
Do you know what your gas and electricity rates are? Gas is sold (usually) by the MJ and electricity by the kWh.  
Assuming 94% efficiency for an unflued gas heater versus 300% efficiency for a reverse cycle A/C, 11.5 MJ of gas will be equivalent to 1 kWh of electricity. 
If comparing with a flued gas heater, you'll typically need around 13.5 MJ to equal 1 kWh (assuming the flued gas heater is 80% efficient - they do vary quite a bit). The higher gas usage is because some heat eascapes out the flue whereas that doesn't happen with an unflued unit. 
So all you need to do now is find out the cost of 1 kWh (electricity) and the cost of 11.5 MJ (gas - unflued) or 13.5 MJ (gas - flued) and compare them to see what the relative costs are.  
There's also a personal preference issue that varies with locality. Victorians tend to like gas, Tasmanians tend to like electricity. Most homes in Melbourne have gas heating, even those with air-conditioners installed. But in Hobart where most have electric heating, people commonly install air-conditioners for heating use only with cooling mode rarely if ever used.  
People in both cities will tell you that their method is best - and as a Tasmanian I'll have to say I'd have reverse cycle A/C over gas any day. Those in Vic will probably disagree...  :Biggrin:

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## GraemeCook

Good Morning Marty 
I would like to add a little to what Smurf has said. 
You also need to consider the installed capital costs of both - you can buy a lot of gas/electricity with a $1,000 cost difference. 
Secondly, a gas heater is purely a heater, a heat pump is both a heater and a cooler - you are in Sydney so cooling is probably more important than heating.   This additional benefit might favour the heat pump. 
Cheers 
Graeme

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## murray44

We bought a house a few years back that had only 1 split system. It heated OK but wasn't really good, seemed to keep blowing cool-ish air when it had reached operating temp. 
We have since added 2 unflued gas heaters, we are now spending about the same money on combined bills but the house is way warmer. 
the moisture may be an issue for you, Canberra is generally very dry.

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## strassenkoeter

A reverse cycle AC does blow heat from the top which is not very healthy. Heat should always be radiation heat. But Sydney isn't very cold so this might not be important. Gas heaters are quite expensive.

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## martyjames

Wow- thanks very much all for the very informative replies and thoughts. I will do some calculations , but seems initially at least i'll run the r/c aircond before committing to buying a gas heater 9and getting a new otlet installed which would be another few hundred dollars!!) 
May thanks again 
cheers 
Marty

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## Uncle Bob

> We bought a house a few years back that had only 1 split system. It heated OK but wasn't really good, seemed to keep blowing cool-ish air when it had reached operating temp. 
> We have since added 2 unflued gas heaters, we are now spending about the same money on combined bills but the house is way warmer. 
> the moisture may be an issue for you, Canberra is generally very dry.

  We have both. We used the R/C last winter which worked well enough but found the same issue with cool drafts. Another thing was the air got too dry and caused static problems. Every time one of the kids jumped on us we would get a belt from the static.

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## Bloss

These replies should tell you something - look at the locations of the posters (its why those with a location like 'Australia' often aren't as useful). Canberra is not a suitable climate for heat pumps alone to provide winter heating (excluding ground source or water source heat pumps which almost no-one has) because their performance drops off dramatically under 10 degrees and is effectively zero -10 degrees. Canberra average maximums in winter are around 12. So in Canberra and other cool temperate climates you need some other heating capacity. I would argue that there is no need for cooling based on fossil fuel energy systems at all, but that's another issue. 
In Sydney where you live you'd have to ask why you need much heating or cooling at al when good design would give very comfortable living, but that too is another discussion. Sydney has a warm temperate climate so reverse cycle heat pump systems are a good choice (not the best) and IMO you would be wasting your money putting in gas heating as well. 
Whatever you chose make sure you do the other things that cost less and give greater overall year round comfort - external shade for summer and also sun access (insolation) in winter, insulation in ceilings and walls, ceiling fans etc, heavy curtains to control summer sun ingress and winter heat loss and all the other passive thermal design stuff. This site is still a good one and has example of what works in Sydney. Your Home Technical Manual - Home Page  :2thumbsup:   I still reckon that for most of us Billy Connolly was right when he said "There's no such thing as 'bad weather', just wrong clothes!". That equates to 'There's no such thing as a cold or hot house,  just a badly designed one!".

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## Smurf

> These replies should tell you something - look at the locations of the posters

  Indeed. 
If you're in Queensland then basically any heater will be good enough for the relatively infrequent use it will get. It's just not something anyone is realy going to worry about too much. 
Tasmania, on the other hand, is very different due to the climate. You either have an economical means of heating, or you have a house that doesn't need much heating due to design, or you spend a fortune trying to keep warm each Winter, or you sit and shiver. They are the 4 choices - very different to a warmer climate where it won't really matter.

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