Gas vs HeatPump Heating

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#657392 18-Jul-2012 08:49

Flued works well as the flues are double walled. Intake air is drawn down one leg of the flue while exhaust gas is pushed down the other leg. This has 2 benefits. The first is that you aren't touching the atmosphere in your house. The other is that the flue acts as a (low efficiency) heat exchanger by cooling the exhaust gas and preheating the intake air via conduction though the flue.

If I had the opportunity to start from scratch with a house, and had reticulated gas, I would probably go for either a gas central heating system, an inslab underfloor heating system with a gas boiler or a radiator system.

There are califonts (i.e. infinity hot water) available which have a secondary side which can be used to heat water for radiators. The concept here is that you only have one piece of plant for heating domestic hot water and your radiators. Adds 25% ish + the cost of the radiators and pipework onto the cost of your instantaneous hot water system but also heats your house.

To me only heating the lounge is a waste of time. If you want a warm home you need to look at the whole floor plane and figure out how to efficiently heat the whole thing. We spend as much heating the bedrooms with oil column heaters as we do heating the lounge with a heatpump.

scuwp

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#657402 18-Jul-2012 09:06

There was a comment earlier about a gas 'fire' which I assume relates to one of those imitation real fire places. We have one of those in a separate lounge and it doesn't heat up much more than just the room it is placed in. Wouldn't consider for heating a house at all. Looks nice though.

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Niel

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#657715 18-Jul-2012 15:32

davidcole: Definitely go flued and fan assisted if going gas. We have a large - 1983 Manufactured Flued Gas heater in the lounge, can wam pretty much the whole house about about 30 mins if the doors are open. Is only just needing a new fan now.

Next time install another 1983 model as they seem to last for ever ;-). I wonder if there is any info on longevity of a modern unit. But as an electronic engineer I agree with electronics not lasting as long as mechanical solutions. Brand name is a good start.

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MikeB4

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#657719 18-Jul-2012 15:35

We have been considering this of late we are tosing up between Flued Gas Panel, hot water radiators or heat pumps. It is almost impossible to get unbiased advice on this and it costs a lot of money to discover you have got it wrong.

Niel

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#657827 18-Jul-2012 16:59

With any option if you buy new you will end up equal. It is a personal preference, whatever makes you happy. Lower running cost is offset by higher up-front cost and/or shorter life. Products are priced that way. Unless you get a really good deal or "mates rates".

Whichever option you go with, don't just go for the cheapest option (i.e. buy quality) as you will have to use it for a number of years.

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richms

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#657832 18-Jul-2012 17:05

If you get an infinity watch for water temperature shifts if you have it plumbed into multiple bathrooms etc as the demand on the water changes. Friends ended up getting a second one installed since turning on the kitchen tap caused a massive cold blast come thru till the infinity ramped up to cope.

Richard rich.ms

hewittj

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#658030 18-Jul-2012 21:38

Hi there

Just wanted to say thanks for all the useful feedback its most appreciated. We have been doing some comparisons of running costs and are finding that the running costs are very close between gas and electric heat pump.

For our specific installation we are leaning more towards gas as we have limited outdoor space near our main living area and by choosing a vertically orientated gas heater we can slot it into a part of the room that is out of the way rather than having the heat pump in a high wall location.

Anyways once we are installed and have an idea of running costs I will be sure to add some details here.

Thanks
Justin

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Jaxson

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#658046 18-Jul-2012 22:05

Niel: But gas cost per kwh (equivalent) is roughly the same as electricity per kwh so with a heat pump using power to transfer heat rather than generating heat, the running cost will probably be about 1/3 of gas.

Sorry but this just not right.

See Regs comments below.

Regs: i pay 6 cents per kWh for gas, and around 25-28 cents per winter kWh for electricty. (i was already paying for the gas pipe (hot water & cooking) so its pointless trying to factor daily charges into a calculation to make gas sound more expensive). even with the extra efficiency of the heatpump i still reckon its cheaper to run my central gas unit

Couple that with gas being a consistent efficiency at all temperature vs heat pump efficiency varying as the indoor to outdoor differential increases. That means you need to be wary of overly simplified comparison calculations etc.

Heat pumps are all the rage but watch closely what is real versus advertising spin. Either approach is capable of heating your space and there's no huge right/wrong answer to it all.

nakedmolerat

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#658055 18-Jul-2012 22:25

Regs:
nakedmolerat: Go for heat pump... It is way better than gas.

why? because you said so?

perhaps you could add the reasons why you think that...

in many scenarios a heatpump may well be better than gas. not always though.

1. work as a heater, dehumidifier and air conditioner

2. i dont know about cost, mine run from 4am - midnight every day during winter. last bill was only ~$360

timmmay

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#658085 18-Jul-2012 23:06

Jaxson:
Niel: But gas cost per kwh (equivalent) is roughly the same as electricity per kwh so with a heat pump using power to transfer heat rather than generating heat, the running cost will probably be about 1/3 of gas.?

Sorry but this just not right.

See Regs comments below.

Regs: i pay 6 cents per kWh for gas, and around 25-28 cents per winter kWh for electricty.? (i was already paying for the gas pipe (hot water & cooking) so its pointless trying to factor daily charges into a calculation to make gas sound more expensive).? even with the extra efficiency of the heatpump i still reckon its cheaper to run my central gas unit

Couple that with gas being a consistent efficiency at all temperature vs heat pump efficiency varying as the indoor to outdoor differential increases.? That means you need to be wary of overly simplified comparison calculations etc.?

Heat pumps are all the rage but watch closely what is real versus advertising spin.? Either approach is capable of heating your space and there's no huge right/wrong answer to it all.

Remember heat pumps are 300 to 400% efficient, meeting them Similar to gas.

richms

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#658087 18-Jul-2012 23:10

3-400% at minimal difference. As it gets cold that falls. As you take it closer to full power it falls. Ok for mild auckland. Not so good down south.

Richard rich.ms

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#658089 18-Jul-2012 23:17

nakedmolerat:
Regs:
nakedmolerat: Go for heat pump... It is way better than gas.

why? because you said so?

perhaps you could add the reasons why you think that...

in many scenarios a heatpump may well be better than gas. not always though.

1. work as a heater, dehumidifier and air conditioner

2. i dont know about cost, mine run from 4am - midnight every day during winter. last bill was only ~$360

The problem with blanket statements is... they are blanket statements. Whether a heat pump is better or worse in any given situation depends on all the factors involved.

In some areas of NZ, for example, heat pumps work out to be both terribly inefficient and very expensive, simply because the areas have high humidity and dew points that are above zero (think Waikato and Manawatu here - both areas where heat pumps are not good heating choices, despite their popularity).

I was advised that in Palmerston North heat pumps can spend more time defrosting than heating, and in defrosting mode the power usage really ratchets up. Then, in April, Consumer came out with a FAQ to explain why this happens:
http://www.consumer.org.nz/reports/heat-pumps/heat-pump-faqs

The other factors to consider are suitable walls for placement, whether the house is fully (and properly) insulated or not, and the local cost of electricity.

As to costs, Consumer put out a comparison graph, as at April 2012:

http://www.consumer.org.nz/reports/heating-options/fuel-prices-compared

Regs

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#658112 19-Jul-2012 01:52

if you look for a flued gas heater, its probably going to cost you about $5000 installed and it will only heat one room.

You can get a central gas heating option installed for around $8000 (depending on brand + options), the heating unit lives outside the house (no flue needed), and you get the whole house heated.

Not sure what the average cost of a single heatpump installed is.

When i was looking, it was going to cost around $20K - $25K for heatpump central heating installed.

central ducted heating - whether gas or heatpump driven - is much better looking install that either a single heatpump or flued gas heater hanging from the wall...

The first place you need to start is figuring out how much you want to spend and whether you're going to be living in the current place short-term, or long term. If long term, then looking to pay more for a central heating option might be worthwhile :-)

P.S. if i was building a house from scratch, i'd probably look into one of those heated water pipes running through the concrete slab systems, with the boiler running on either gas or heatpump. I believe thats a pretty good and efficient way to heat a house.

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Niel

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#658119 19-Jul-2012 06:03

Jaxson:
Niel: But gas cost per kwh (equivalent) is roughly the same as electricity per kwh so with a heat pump using power to transfer heat rather than generating heat, the running cost will probably be about 1/3 of gas.

Sorry but this just not right.

Agree, this was an older post of mine. A newer post states it will be similar cost, which someone else also stated.

Something to keep in mind is depending on your electricity provider you can get a large discount if your ripple controller can control your electric hot water cylinder. If you do not have an electric cylinder then your ripple controller is pointless and then you cannot get the reduced rate. If you cannot find info about ripple control rates on your electricity retailer's web site then phone them because they all have the option but some (most?) do not advertise it as they will make less profit. But it is on the "what's my number" web site.

We built a new house on our section and then removed the old house. We were with Mercury for over 10 years, but with the temporary 2 houses at one address we had to open a new account and then close the old. In the process we were placed on the standard rate. I've discovered this after 6 month, phoned them, and they put me on the reduced rate plus credit the difference of the 6 months I was on the normal rate (and I did not ask for compensation, it was just offered).

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timmmay

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#658140 19-Jul-2012 07:58

A Fujitsu ducted heat pump to heat three rooms, call the night pump I think, is $7-$10K. Larger ones get a lot more expensive.

The largest 8-11kw Fujitsu Nocria (which has a pretty high output) costs about $4K installed. A smaller one might cost $2500 - $3500.

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