Green Oversite



The All Electric House

By Bruce Barbour - February 2020, revised April and September 2021

When I walk around new estates it still seems that connecting gas to new houses is still very popular. It seems that builders put this in by default - because that is the way they have done it for the last umpteen years - and it may still be the cheapest in terms of initial build cost. However a number of recent studies have suggested that economically and environmentally it is better to go all electric. I certainly did when I built my new house 3 years ago - a decision that I am very happy with.

Here are three of the reports/ articles:
There is also a Facebook group called "My Efficient Electric Home" that is worth a look. If you are not a fan of Facebook you don't have to be registered with Facebook to be able to read this page.
Rather than just relying on the above reports before I go on I will look at why it is worthwhile to go all electric.

Financial: - Gas costs 3.53 to 2.31 cents per MegaJoule (MJ) - AGL Victoria "freedom" tariff inc GST - January 2020. The lower rate is for larger usage. Say electricity purchased from the grid costs 30 c/kWh. This is equivalent to 8.3 c/MJ (30/3.6). I hear you say - this is still more expensive than gas. Yes it is but when you account for the efficiency of use the story changes.

For gas you might have (generously) a 84% efficiency for the very best in room wall mounted gas space heater (with exhaust gas flue). If using ducted heating this efficiency will be a lot lower - 60 to 70% or even lower allowing for heat loss from the ducts from conduction and heated air leakage and energy to run the system fan. For electricity used by heat pumps (for water and space heating) you should get an efficiency of 400%. This can be variable - depending on the make and model of the heat pump and also the external temperatures. I also assuming the use of split reverse cycle air conditioners - rather than ducted reverse cycle air conditioners - which if used would still have duct heat losses lowering the efficiency - but then so would a natural gas ducted heating system. Using these factors the usable heat cost per MJ of gas is 4.2 to 2.75 c/MJ.  The heat usable cost per MJ for electricity used for heating with a heat pump is 2.1 c/MJ. Heating using an efficient heat pump run by electricity is cheaper.

There are other factors that further improve the favourability of electricity. If the electricity to run the heat pump is supplied by a roof top solar photo voltaic system (PV) then the marginal cost of electricity while the sun shines is zero - or if you consider the loss of income from selling that electricity back to the grid, 10.2 c/kWh (the Victorian standard solar feed-in tariff) instead of 30 c/kWh. On site generation is not an option for natural gas (unless you live on a pig farm!).

Further, if you have no gas to your house you don't have to pay the quarterly connection fee of approx. $90 ($360 per annum).

Old and poorly maintained appliances in houses may leak gas. For this reason it is recommended that gas appliances be checked by a technician every two years. This adds to the cost of having gas appliances. This type of checking is not required for electrical appliances.

Most of the commentators that I have read, including AEMO, predict that the cost of natural gas in Australia will increase substantially over the coming years. All in all, electricity is a better financial proposition at present and will improve even more going forward.

Environmental: - This is less straight forward than the financial comparison. Natural gas - primarily methane - has a carbon content of 0.051 kg(CO2)/MJ just considering the gas itself and not the carbon needed to produce it and get it to your door. Electricity in Victoria has a carbon content of 1.02 kg/kWh or 0.28 kg(CO2)/MJ (see Note 1). This is 5.5 times the carbon content of natural gas - due to the use of Victoria's dirty brown coal for generating most of the electricity. When the efficiency of use coefficients are applied (84% for gas and 400% for electricity used through a heat pump) the comparison is 0.061 kg(CO2)/MJ for natural gas and 0.07 kg(CO2)/MJ for electricity. Using this analysis gas seems to still have an advantage (14%) over electricity generated from fossil fuels in Victoria. However there are a number of factors that make this not so:
  • the extraction and distribution of natural gas leads to what are called (in some cases mistakenly) fugitive emissions. That is gas - which is largely methane - that leaks or is released into the atmosphere. On occasions as part of the gas extraction and production process methane may be deliberately released into the atmosphere. The industry may also deliberately release carbon dioxide and methane into the atmosphere as often with lower quality gas fields the gas contains a mixture of both methane and carbon dioxide. The carbon dioxide is vented off into the atmosphere as a waste material and may take some methane with it. This is worse as the gas fields get to their end of use and contain lower quality gas, and also with newer extraction methods such as fracking. With the the thousands of kilometres of gas distribution pipelines there are undoubtedly leaks of the gas (methane) into the atmosphere, small and large. The size of the release/escape of methane and carbon dioxide during production and distribution is unknown - or if it is known it is not being told to us by the industry. Watch the video for further information. Mass for mass methane has a lifetime warming impact 28 times that of carbon dioxide over a 100 year period (though this figure itself is misleading as methane dissipates out of the atmosphere in a decade or two so the short term impact compared to CO2 is much higher than this - potentially over 80 times the impact of CO2).
  • Old and poorly maintained appliances in houses may also leak - a direct health hazard to the house occupants as well as having a longer term environmental impact.
  • if you use electricity from a roof top solar PV system or you purchase "green power" then the amount of carbon produced from that electricity is much lower (if not zero).
  • And remember I have used a high gas burning efficiency - it can be a whole lot worse - especially for ducted systems.
  • The grid is converting away from fossil fuels to renewable energy, which has a much lower carbon impact. The World is coming to the realisation of the necessity to be 100% fossil fuel free by 2050 if not before. In Victoria it has been announced that the Yallourn power station will close by 2028. Yallourn represents 30% of Victoria's generation capacity. It is certain that this capacity will not be replaced by other fossil fuel generators. Instead it will be replaced by renewable energy generation and batteries. I anticipate that as more renewables come on line Yallourn will be phased out rather than the switch being thrown to off on all generating in 2028. (If a generating unit breaks down a couple of years before the deadline and would cost a fortune to repair the owners will decide to decommission it instead.) By 2028 we can anticipate that the average carbon content of Victoria's electricity will be 0.7 kg/kWh (0.19 kg(CO2)/MJ) or less, rather than the present 1.02 kg/kWh (0.28 kg(CO2)/MJ). The Victorian Government has also recently (May 2021) announced a target of a 50% reduction in green house gas production from 2005 levels by 2030 which would indicate our electricity should be below 0.5 kg/kWh by this date and 0.0 kg/kWh before 2050. These factors will make the environmental impact calculations much more favourable. Within a few short years even a simplistic calculation of greenhouse gas emissions such as provided at the start of this Environmental section will favour the use of electricity over methane.
  • Because it is such a big project to convert all the houses with gas to electricity - which must occur to become 100% fossil fuel free - and the timeline relatively short, the community cannot wait until the grid is 100% renewable energy and then start the conversion of gas heated houses to all electric. There would not be enough time. Both have to occur simultaneously. (This is a similar situation to the conversion of the internal combustion car fleet to electric vehicles.)
  • If the World is to achieve 100% conversion from fossil fuels then all natural gas use in homes has to go at some point. Might as well convert early as later. Make the cost savings and help close down the gas industry in the medium term. Lowering the demand for natural gas will mean that the industry will close down quicker.
Note 1: I was surprised that the amount of CO2 from Victorian electricity is still calculated as 1.02 kg/kWh. Over twenty years ago when I was doing a course on renewable energy the figure I was using then was 1.1 kg (CO2)/kWh for Victorian grid electricity. There has been a heck of lot of renewables introduced in intervening 20 years which I would have hoped would have reduced the average carbon content by more than 8 percent. However I can only use the figures published. As more renewables are introduced - as they have to be if we are to have any chance with climate change - and the coal power stations close down - this figure should improve. Ultimately we must be aiming for complete decarbonation of the economy, and this includes natural gas for domestic use. The figures for other states are lower than Victoria, ranging from 0.15 kg/kWh for Tasmania (due to all of their hydro) to 0.81 kg/kWh for NSW making the use of electricity more favourable in other states.

Note 2: If converting an existing house to all electric or building a new house  there are a couple of things to keep in mind. In Victoria especially you should include adding a PV system, if the house does not already have one, or allow for the purchase of 100% “Green Power” – preferably both. If shifting from a gas hot water service the new unit should either be solar thermal or (preferably) a heat pump. To just shift to a storage heated by an electrical resistance element (if these are indeed still available) would be retrograde step (unless this is to be substantially powered from the roof top PV system). Heat pumps should be used for the main heating functions – hot water and space heating. Resistance (preferably radiant) heating can be used for short term spot heating – say in a bathroom. Install an induction cook top.
One of the issues in Victoria when I was building my new house was that there was a silly regulation in place  that said that if you did not have a gas boosted solar hot water system you had to have a minimum 2kL rainwater tank - I assume that regulation is still in place. So there is an additional cost of a couple of grand to do that if you were not initially intending to have a rainwater tank but even with this requirement going all electric is still worthwhile. And having a rainwater tank has some benefits. (I have since been advised that this regulation can be worked around - I don't know how.)

If you do go all electric it is best to have a heat pump hot water system - with a reasonable storage tank size. When used in conjunction with a solar PV system with the hot water system set to heat in the middle of the day it works well. (Make sure you purchase a heat pump system that can be put on a timer to heat during the day.) The PV should be at least 4 times the size of the energy use of the heat pump so that even in Winter the PV system will generate enough electricity to run the heat pump on the majority of days - so long as other usage is minimised in that period. (In winter I have programmed the room heater to turn off at the time the hot water system starts up - at 11am. If there is sufficient sun it will be providing sufficient heating for the house from that time, if not earlier. If not, I will turn the AC heater on a couple of hours later, when the water heater has finished. This is of course not mandatory - you can run them both simultaneously if you need the heat in the house - you may be using more grid electricity rather than the cheaper PV.)

If you have a good cook in the house it would be worthwhile investing in an induction cook top rather that a cheaper electric cook top. Also make sure any electric oven you purchase does not blow hot air into the room like my model does (making it unusable on warm summer days and inefficient on all other days). Ovens do not have an energy star rating, which means the manufacturers can get away with lower energy efficiency standards, with efficiency comparison to other brands and models difficult. But that is another story. For some reason quite a few of the modern units available blow heat out - so you may be stuck with this "feature".

Also use split RC air conditioning for heating (and cooling) - probably multi-head to allow for zoning which sections of the house are heated. It is more efficient than ducted due to losses in the ducting and more difficulty in zoning. The RC units should use inverter technology - I think most of them do but it is best to check. Inverter technology allows the RC unit to ramp up and down depending on the amount of heating (/cooling) that is needed. The alternative is that the unit is either working at maximum power or switched off on thermostat - an arrangement that is inherently less efficient than an an inverter system for RC aircon and allows greater temperature variation in the room.

Think about how the house will be used and install additional doors if necessary to allow zoning.

A parting quote:

"There is no pathway to stabilising the climate without phasing gas out of our homes and buildings.  This is a must-do for the climate and a liveable planet." 

- Rachel Golden of the Sierra Club

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