Gas for a new build

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474 posts

Ultimate Geek

#1337602 6-Jul-2015 09:34

not sure where you got pricing from but ours is definitly cheaper on lpg than mains here in tauranga

mdf

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#1337624 6-Jul-2015 09:38

Because of the pricing structure of reticulated gas (high fixed daily charge, but low variable per unit charge), it only makes economic sense to have gas installed if you use it for pretty much everything - hot water, cooking and heating.

We have an infiniti hot water system (great with the kids spending hours in the shower), a large flued gas heater that heats most of the house, and gas cooktops. We went with an electric oven since you get better temperature control. We love it and wouldn't go back to electricity. The "instant heat" of the gas heater in particular is great (cf. the constant temperature of heatpumps). Friends of ours with a larger house have a really nice gas central heating solution and rave about it.

From an environmental perspective, if you're in Auckland, at least some of the time you're getting electricity from the gas fired Huntley power station. It's better from an environmental perspective to pipe gas to your house and generate energy (heat, in this case) at the point of usage, rather than converting it to electricity at the station and sending it down the wires. There's a lot less transmission loss, and you get a much higher conversion ratio going from gas --> heat rather than gas --> electricity --> heat. From memory, the efficiency ratio of modern gas appliances is around 90%.

That said, with increasing prices it's not the economic no-brainer it once was. If you have most of your heating and hotwater on energy efficient options (i.e. heat pumps), and only want a gas hob, you don't actually need the big (45kg?) cylinders. You can get hobs that run off a BBQ cylinder (9kg?). Keep it in the kitchen cupboard with a spare and you're sorted - no rental or delivery fees. I think hobs that do this are usually advertised as being "dual fuel" but don't hold me to that.

Electricity and heat pumps also gives you the option of summer air conditioning, which may be a bonus further north.

In terms of the heat of reticulated vs LPG, I've not heard this before but I don't think it matters. You just adjust your thermostats / cooking flame to suit.

floydie

474 posts

Ultimate Geek

#1337637 6-Jul-2015 09:46

the jets are different sizes for lpg/nat gas but you end up with the same BTU if youve jetted it right. we very nearly went with ducted gas heating as it is a great option but went with the heat pump for cooling in the summer. having no gas heating meant the decision for bottles was easy. if we'd done gas heating too we'd have gone on mains

Jaxson

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#1337660 6-Jul-2015 10:07

The two biggest consumers of power in your home will be hot water and heating.

Going gas only tends to make sense if you put everything onto it, as in hot water, heating, cooking. You're paying a line charge regardless of how much you use.

Gas tends to work out the same as running a heat pump for heating, especially if its cold outside, where heat pumps lose their efficiency.
Some models continue to work when it's really cold outside, but certainly not at the '300% efficient' level they're marketed at.
You don't get any cooling capability in summer with gas, which saves you money too, but is of no use during a hot summer day.

I do wonder if direct online solar PV is the way to go long term. By using time clocks you can ensure your hot water is only heated during the daylight hours of the day. It would be interesting to see if you have enough capacity available to make this work for evening and morning showers. Physical hot water solar looks to be on the way out, because you can use that same solar energy for electrical use throughout the home, and not just link it to water only.

Solar PV matches the loads for summer cooling with a heat pump really well, essentially giving you free cooling when it's a hot summers day for example.

A bit off track there, only mentioned because you said this was a new build. If I was new building, I'd be looking at layouts of the home to benefit from sun angles, some passive elements like overhanging roofs to block high summer sun, but allow low winter sun in etc, and maybe a wood burner close to a hot water cylinder with a wet back etc. New builds allow a lot of design decisions to cut your energy requirements, if you align for the sun and not just the road frontage etc like we love to do in NZ.

Aredwood

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#1338202 7-Jul-2015 00:40

floydie: not sure where you got pricing from but ours is definitly cheaper on lpg than mains here in tauranga

Since a 45Kg cylinder has 614 kW/hr of energy. And if we assume that it costs $100 per cylinder including delivery to your house.

$100 / 614kW/hr = $0.1628 per kW/hr or 16.28c per kW/hr/

And Genesis have Natural gas available is Tauranga for 6.37c per kW/hr (Price is excluding GST but before prompt payment discount, Cant be bothered looking up what their prompt payment discount is) And previously Contact have had even cheaper gas prices. But their website is horrible now. And I Don't want to try calling them just to ask what their gas prices are at the moment.

Either way, Natural gas is far cheaper than LPG. (On a per kW/Hr basis) Although agree that for low users LPG will still be cheaper after the fixed fees are factored in.

elpenguino

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#1338956 7-Jul-2015 23:16

I do wonder if direct online solar PV is the way to go long term.

_____

Are you suggesting generating electricity with photo voltaics to heat water? I would have thought a panel efficiency of 20% or less would make that very uneconomical....

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

floydie

474 posts

Ultimate Geek

#1339339 8-Jul-2015 16:09

when we looked at it. it was averaging at 80-90 dollars a month on natural gas and we are at $53 a month on our current useage. if you are heating your home too then go with natural gas. the install cost was also thousands more for natural than lpg.

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surfisup1000

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#1339384 8-Jul-2015 17:15

I'm on gas -- house built 7 years ago.

I don't think it's worth it. The daily fixed charge pretty much kills the economics.

My latest bill is $750 (400 gas plus 350 electricity). The gas is usually around $50 in summer, winter is higher due to underfloor heating which costs around 350 a month to run in winter.

Underfloor heating is rubbish too - they sold us on how efficient it would be, unfortunately the sales people are long gone and we are left to pay the bills.

DarthKermit

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#1339400 8-Jul-2015 17:30

Are gas hot water cylinders available in mains pressure versions?

Aredwood

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#1339595 9-Jul-2015 00:01

DarthKermit: Are gas hot water cylinders available in mains pressure versions?

Definitely. You can't even get low pressure gas hot water cylinders anymore.

Get the Rheem Stella outdoor cylinder. They are far more efficient than indoor gas hot water cylinders.

bazzer

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#1339700 9-Jul-2015 09:35

surfisup1000: I'm on gas -- house built 7 years ago.

I don't think it's worth it. The daily fixed charge pretty much kills the economics.

My latest bill is $750 (400 gas plus 350 electricity). The gas is usually around $50 in summer, winter is higher due to underfloor heating which costs around 350 a month to run in winter.

Underfloor heating is rubbish too - they sold us on how efficient it would be, unfortunately the sales people are long gone and we are left to pay the bills.

If you're using that much gas, I can't imagine how the daily fixed charge would be material. The daily charge is still around $30 so the usage part is $370, that one month is probably enough to warrant natural gas over LPG even if all the other months were $50 months.

Ditto for electricity, underfloor heating is expensive, is that a surprise? If you'd gotten electric, would it have been any more efficient? Probably not, so you just end up paying even more to heat it in electricity.

My calcs could be wrong, and I'm basing on Auckland prices, but the idea probably holds elsewhere (at least to a degree).

Jaxson

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#1339945 9-Jul-2015 13:11

You don't have to use underfloor heating if you don't want to. You could argue you paid a capital cost upfront for it when you purchased the house, assuming it was considered to have added value to the property, but you simply do not have to use it now if you don't want to.

Typically it will take a lot to heat up the floor slab, but it should retain this heat for a while, so the system should ideally button off. Maybe you should investigate to ensure it's working correctly, to lower the setpoints, or consider upgrading the control system? Maybe it's in need of some maintenance to ensure thermostats are still working correctly etc.

Bazzer I think that's the monthly charge of $30, not the daily charge...
Essentially though, the more you use the lower the impact of the daily charge on the total bill, which is why I said it's effective if you're going to go the whole way to include heating, hot water and cooking on gas. Gas for just one of those items alone means the daily charge really does become something to consider.

As an aside, for anyone building new, I'd seriously recommend investigating direct online Solar PV instead if you are considering solar for your hot water. With an electric element on a time clock control you can still use the solar energy to heat your water, but it's also available for other use, such as air con during summer.

Hammerer

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#1339983 9-Jul-2015 13:51

floydie: the jets are different sizes for lpg/nat gas but you end up with the same BTU if youve jetted it right. we very nearly went with ducted gas heating as it is a great option but went with the heat pump for cooling in the summer. having no gas heating meant the decision for bottles was easy. if we'd done gas heating too we'd have gone on mains

+1 As floydie points out CNG and LPG are not interchangeable when it comes to cooking hobs. You need the correct jets for each gas.

CNG and LPG are different gases with different characteristics. One of the biggest issues is safety. In a residence I would always prefer CNG (methane) over LPG because CNG leaks disperse more easily. LPG (butane / propane) is heavier and pool in low points. LPG is also used at higher pressures which probably contributes to some of the safety issues. But for an outdoor BBQ, where the dispersal of leaks is less difficult than indoors, I would always go for LPG particularly where I can get butane which gives more energy - that extra 12% or so of heat makes a lot of difference on a windy day.

Jaxson:
As an aside, for anyone building new, I'd seriously recommend investigating direct online Solar PV instead if you are considering solar for your hot water. With an electric element on a time clock control you can still use the solar energy to heat your water, but it's also available for other use, such as air con during summer.

+1 As a user of solar water heating (with evacuated tubes) I would prefer to have solar PV now that the prices are more economic. The benefits of flexibility outweigh the lower efficiency. In summer we have to run off 80C water on many summer days. With solar PV we would have more options to use that excess energy.

bazzer

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#1339995 9-Jul-2015 13:58

Jaxson: Bazzer I think that's the monthly charge of $30, not the daily charge...
Essentially though, the more you use the lower the impact of the daily charge on the total bill, which is why I said it's effective if you're going to go the whole way to include heating, hot water and cooking on gas. Gas for just one of those items alone means the daily charge really does become something to consider.

Yes, sorry, I didn't make my point clear. I meant that on the monthly bill of $400, about $30 would be the daily charge ($1ish x 30ish) so the usage of $370 means a significant saving compared to LPG and electricity (on a per kWh basis). Enough to mean the daily charge is immaterial in comparison, probably over the entire year even. In other words, I agree with you.

It's pretty straightforward to figure out the usage bands that correspond to the cheapest source, the same as deciding low-use plan over high-use. For our house, technically we'd be better off on LPG bottles, but there's not much in it and this way we'll be better off if usage increases.

andrew027

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#1340062 9-Jul-2015 15:27

mdf: If you have most of your heating and hotwater on energy efficient options (i.e. heat pumps), and only want a gas hob, you don't actually need the big (45kg?) cylinders. You can get hobs that run off a BBQ cylinder (9kg?). Keep it in the kitchen cupboard with a spare and you're sorted

I know people used to do this, but I'm about 99% sure it's not legal to have the cylinder in your kitchen any more - it has to be outside. Maybe someone else can confirm?

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