Our energy-efficient all-electric home

Let's get something out of the way first: Our planet is burning, driven especially hard by our reliance on fossil fuels. Where I live in Victoria, Australia, we have historically relied on burning black and brown coal to power our state electricity grid. This is certainly a Bad Thing^TM. If you feel this is controversial, then I encourage you to stop reading now as you'll only get to the bottom and want to come tell me how much money I've wasted. Go away, I am not interested in that discussion.

I'm thankful that our household is in a position to do what's documented below. Being able to put my money where my mouth is won't make a dent in our country's disasterous CO2 emissions, but I hope that it's one of many small steps that individuals can take to help show how valuable energy efficiency is and how well we are actually able to adapt to clean energy here in Australia.

Do I think everybody should do this? No. Do I wish that everybody could do this? Absolutely. Do I wish that none of us needed to, because of improved building standards and a cleaner energy grid? Hell yes.

So, with that preamble out of the way, what have we done and what's been the end result?

If you're in a rush, jump to the costs and ROI calculations. Otherwise, grab a cuppa and read on...

Some background on what we were trying to achieve

In my 2022 running review I touched on the purchase and planning process for a new home we wanted to build, ideally to Passive House / Passivhaus standards. We wanted a home that not only met the needs of our family for the next decade or two, but was cheap to run¹ and comfortable to live in².

We decided to walk the walk and build a home that we hoped could be a workable example for others.

The short version of what came next was in that year-in-review post:

We decided in 2021 to build a new house and by mid-2021 we'd bought a block of land and started working with Passivehaus building designers. We had lofty aims and wanted a high quality home. We sold our family home, which was the only home our kids had ever known, and moved into a freezing cold rental home.

One key stress related to building a home was the rapidly escalating cost - due in no small part to builders attempting to recover financially from Covid and by materials shortages caused by a combination of an unexpected war and general supply chain bed-shitting.

So we added to do something about our stress. We decided to sell the land (we hadn't yet started building due to worry about costs) and buy an established home instead - which leads, inevitably, to multiple weekends of house inspections and stressful decision making - but it resulted in us landing in a comfortable family home that has given us some stability back.

It was, initially, heartbreaking to walk away from our build project.

After a few months of house hunting, we came across a home in an eco village that met many of our needs. It wasn't fully electrified, and it wasn't a Passive House, but it was pretty close and we decided it'd be a great canvas for us to work with.

The house has its bedrooms and living areas facing to the north³, and utility areas to the south. The garden space is mostly to the north of the house.

Photo: The front of the home we purchased. Photo taken at the tail end of Summer - the white netting is protecting our lovely espalier apple trees from the local birdlife!

Improving the performance of the home

Having a 'clean' or 'efficient' way to heat or cool a home is only part of the problem: if the house itself doesn't hold heat (or cool) well, you're fighting a battle that can only be won by paying ever-larger energy bills. So the best 'bang for buck' with energy efficiency can actually come from areas other than appliances: the home itself.

You want a home to hold heat in winter, stay cool in summer, and ideally allow for some natural heating or cooling. This is achieved with sensible window placement, windows facing North⁴, appropriately sized eaves⁵, good insulation, and no draughts.

In Australia we have a pretty shocking track record of building quality homes. Many houses have draughts - external air moving in and out in ways you don't intend or control - that cause houses to heat or cool quickly. We also have a reliance on cheap single glazed windows.

The home we purchased was around 10 years old. It's a timber frame construction, on stumps with a timber floor. The external cladding is polystyrene foam (the dark gray sections in the photo above) and plywood (the lighter gray sections). The roof and walls, on inspection, are well insulated and the underfloor area has a very light level of insulation in place. The timber-frame windows looked great, but were single panes of glass.

By using two panes of glass with a sealed gas insulating layer between, you can save up to 40% of your winter heat vanishing through the windows. Double glazing also helps address window condensation on cold nights, and reduces external noise. These are all good things.

Our windows were one of the first things we addressed. For a week, our house was covered in scaffolding and tradespeople from DIY Double Glaze. DIY Double Glaze are a local company who specialise in supply and fit of high-performance double-glazed glass units into existing timber frames. This meant we didnt replace our window frames, but only the glass within them.

Adding double glazing had an immediate benefit on sound; the comfort of the house also increased noticibly. Our loungeroom - with a North-facing 3-meter wide window that's 2.1m tall - felt more comfortable. I've got no data or hard metrics to support this but it's impossible to argue with after you've been in the home for a short time.

This was not a cheap exercise. We spent $28,174 for the glass to be supplied and fitted. I have not, even for a second, had any regret or doubt about the spend. I highly recommend DIY Double Glaze for your home if you are looking for this type of upgrade. We include this as part of our capital cost up-front for the home, which makes it easier to justify, but this doesn't make it any cheaper.

Because we didn't live in the house for long before upgrading our windows, we cannot truly calculate a return on investment (ROI). We don't know how much our energy bills have reduced - but we do know the house is significantly more comfortable to live in and (spoiler alert) we only spend $120/year on electricity, so I'm pretty happy that we're saving money as a direct result.

Removing natural gas

Here in Australia, there is a large Natural Gas (NG, or Methane) industry that mines gas from underneath our oceans and pipes it into Victorian homes. It is not at all uncommon for a contemporary house in Victoria to have two or three of:

• Gas cooktop (usually with an electric oven)
• Gas hot water - either a gas-fired tank heater, or 'instantaneous gas' real-time heating powered by a gas burner, or a 'solar' evacuated tube heater on the roof boosted by an instantaneous gas heater when necessary
• Ducted gas-fired heating

Natural gas is a fossil fuel, and burning it in the house is not good for a number of reasons. It is smelly, it is poisinous, and its use generates greenhouse gases. Additionally, it's not cheap: in my area of Melbourne, Australia it costs approx $0.90 per day for a natural gas connection before usage fees. That's $300 per year even if you never light a flame.

Due to the environmental impact of Natural Gas there is a movement to remove it from unnecessary use being led by Dr Saul Griffith. This was reenforced by the Victorian Government's policy to ban gas connections for new homes. We've long been believers in gas being worse than electricity for most purposes (i.e. using a reverse-cycle heatpump is cheaper to run than a gas heater; the environmental impact is also lower if using clean energy sources) and so we were eager to see if we could make this work for us.

Our new home had two gas applicances: a gas cooktop attached to a freestanding 900mm wide oven, and an instantaneous gas hot water heater.

Photo: Our gas meter (surrounded by raspberry canes) prior to being removed.

Switching to electric cooking

Upon moving in we needed to remove the oven/cooktop temporarily to facilitate works on the timber floors. This gave us the opportunity to consider a replacement oven/cooktop.

Our preferred kitchen would have a cooktop installed in the benchtop with a separate oven installed in the cabinetry. However for what we can only assume are asesthetic reasons the builders of our home had used an 'all in one' unit: 900mm wide with a big oven and an attached cooktop. This takes away the ability to replace the cooktop without also replacing the (perfectly functional!) oven.

In our situation the cost wasn't overly friendly, primarily because of the wide all-in-one unit. There are very few options for 900mm wide ovens with induction cooktops. We paid $7,387 for a Smeg unit. This is not cheap, and it's frustrating that somebody's aesthetic decisions a decade earlier narrowed our choices.

For comparison, the equivilant Smeg induction cooktop (without an oven attached) would have cost approx $1,700 - a quarter of the price. The same cooktop (again, without oven) in natural gas is $1,800. Take note here: if you're installing a quality appliance anyway, in a new build an induction cooktop is cheaper than gas!

An electrician to do the install for us cost approximately $500 (to disconnect the previous oven, then return on a later date to install a new circuit from the switchboard to the kitchen for the new oven). Additionally we paid a plumber $140 to disconnect the gas supply from the stove; neither of these jobs are legal to do as an unlicensed tradesperson in Australia.

To avoid waste we donated the old cooker to a homeless kitchen who needed to replace their (identical!) unit that had just stopped working.

A brief aside here; induction cooking is amazing. The temperature control is very precise, there is no 'stray' heat up the sides of the pot, there's no additional humidity added to the room, and the clean-up is approximately eleventy million times easier than the grill and burner in most gas stoves.

Replacing instantaneous gas hot water

This left us with instantaneous gas hot water. Our running costs for this were easy to identify; because the cooktop was removed from the house before we actually moved into it we never cooked with it! To heat hot water cost us approximately $2.00 per day (including supply and usage charges).

We had a better plan than this: we removed the gas hot water heater and installed a Reclaim Heat Pump hot water service. Heat pumps are ✨magical✨. 1kW of energy input results in about 5kW of equivalent heating for the water. Thats 500% efficiency! Energy out of thin air!

Our power metering shows our hot water heat pump runs for approximately 90 minutes a day, drawing approximately 1100 watts for that time. At 40c/kWh (which is a slightly-high-but-normal retail rate for my area on the AusNet electricity network) this costs a maximum of about 66 cents per day; I am comfortable excluding supply charges here as we have many other needs to pay that underlying daily fee anyway.

A timer runs the hot water heat pump at midday. The sun is typically shining at this time so the hot water is using solar power that would otherwise be fed back to the grid. This makes it, effectively, a battery that 'stores' solar power during the day for use at a later time (albeit as hot water, not as electricity). With a solar feed-in tarrif that is currently about 6c/kWh we can carry a daily running cost of 10c/day. The reality is that we are export limited in our solar production, so on clear spring/summer days the true running cost is much closer to $0.00 per day as we are still getting our maximum export payment.

Supply of the hot water system (heat pump unit, 315L storage tank, and controller unit) plus labour (to run a new power circuit from the switch board, remove the gas hot water, and plumb in the new unit) cost us $5,643.99 after rebates.

To calculate payback here we need to consider the price, the $2/day price for gas, and the 10c/day price for electricity. Assuming power prices never change, that $1.90 delta will take 2,970 days - a bit over 8 years - to pay back. That's a payback within the warranty period of the hot water system.

Further, recent trends have shown electricity feed-in tarrifs (i.e. what we are paid for sending our excess solar energy back to the grid) are decreasing and gas consumption prices are increasing. These both cause the payback period to shorten. I will note here that the opportunity cost - i.e. investing - should also come into a payback discussion, but for our situation the 'feel good' value of getting off gas is just as valuable so I'm chosing to ignore that.

Heating / cooling

One thing we didn't have to replace was our space heating and cooling. When it was built, the house had multi-head split-system reverse-cycle heat pump units installed. These provide nice cold air during the summer and warm air in winter.

With the double glazing, these don't have to work as hard as they otherwise would have. This lowers the running cost further and might also increase their lifespan.

The technology for heat pump space heaters is the same as the hot water system above - ✨magic✨. They are incredibly energy efficient to run. When you combine that with solar (see below) they're cheap to run, even during winter.

Actually getting rid of the gas supply

This was a whole debacle that involved many hours of heated discussions with our energy provider. Eventually they removed the gas meter, capped the supply line so it couldn't be used, and left with a smile. This should have cost us $70 to do, but due to the consistent administrative errors and my constant follow-up, the fee was waived - our gas removal cost us $0.00 (and about 30 hours of phone calls - no joke!)

Photo: It's gone! The space our gas meter USED to be. Those pipes go nowhere now!

Generating our own electricity

I mentioned above that we have solar electricity generation to cover our hot water heating during the day. We achieved this by installing a 9.84kw solar system on our rooftop.

It feels like in Australia we have an obsession with complicated roof lines that leave very little uninterrupted roof space. Something we had planned for our new build (that didn't eventuate) was a somewhat "flat" roof at about 10% pitch, with little interruption for peaks and valleys. When we first looked at this house the roof stood out to us as a highlight - gently sloping down to the north and the west, and no interference from trees in neighbouring homes!

We have a strong residential solar energy industry in Australia, and there are government benefits (means-tested, historically available at state and federal government levels at various times). In Melbourne a solar energy system will generate approximately 1676kWh per kilowatt of solar panels per year. The average home consumes 4,400kWh according to that same resource. However not all energy generation occurs when energy is being consumed; the excess energy from a system is 'exported' back to the grid. Homeowners are credited on their electricity bill at a rate approx. 15% of the price of electricity import/purchase⁶.

Soon after moving in to our home we gathered a number of quotes for this work, and ended up using a small local company called Linked Solar to do the installation. We were very happy with Christian's approach and the way he and his team engaged with us during the sales process, the lead-up to installation, on install day, and then with the follow-up actions needed.

We went with the biggest system we were permitted to install by our electricity wholesaler. This turned out to be 9.86kw of solar panels paired to a 8.2kw Fronius inverter. We also had a consumption meter installed to give detailed (and realtime) import/export statistics. I also pay $40 per year for Solar Analytics, a great product that provides very detailed analysis of our system. I also use the Solar Analytics 'Plan Optimiser' multiple times a year to switch energy providers, using our exact usage profile to chase the best deal - Australian electricity providers tend to change their rates on a regular basis so the cheapest provider a year ago is likely not the cheapest today.

Photo: One of four banks of solar panels on our 2nd story roof.

On most days of the year, our sunrise-to-sunset electricity consumption is covered by the solar system. The exceptions are the darkest and cloudiest winter days. On ideal days, we generate approx 4x more electricity that we use, in raw kWh terms. In reality we still import power from the grid to cover electricity use during the evening and overnight.

At the time of install, adding a battery system would have reduced our grid reliance to a very low number however the cost was still prohibitively high for us.

Our out-of-pocket was $13,147 after STC discounts. There were additional state-government rebates running at the time that we were not eligible for.

Solar Analytics has calculated that in 2023, we paid to import $953 of electricity from the grid. We were paid $833 for electricity we exported. We also used electricity that we generated to save a further $999.80 of electricity that would otherwise have been imported.

In real cashflow we paid $120 for the entire year of electricity in 2023. On paper, our total savings was $1,834 for the year. Assuming this is a normal year, our payback period is 7 years. With a system warranted for 25 years (10 for the inverter) we're pretty happy - and as electricity prices continue to rise, we're mostly insulated from that external cost.

Photo: Solar Analytics calculations for our electricity usage in 2023

Changes in electricity behavour

The biggest benefit to having solar power generation is not from the grid export. Over time the legislated feed-in tarrif, i.e. the amount you are paid for exporting excess electricity, reduces (i.e. in 2022 it was 6c/kWh and today it is 5.6kWh minimum in Victoria. Some retailers currently pay 8-11c/kWh). The biggest benefit is from self-consumption: running your appliances when the sun is shining and your system is generating.

The biggest user of electricity in most households is in heating and cooling, of both spaces and of water. By using an electric hot water system (of any type - even the classic resistive units) during the day rather than at night, you're using your own solar generation.

Our heating/cooling is mostly run during the day when the sun shines, except for weather extremes. Our large north facing windows help heat the house naturally during winter, and the well-insulated roof and walls (including that double glazing we splashed out for when we bought the house) cause the home to hold the temperature well.

The next biggest users are large whitegoods - dishwashers and washing machines. These are actually incredibly easy to make the most of: fill them at night or in the morning, and then before hitting 'start' just press the 'delay' button so that it doesn't actually start cleaning until the sun shines. It's basically zero extra effort, but real dollar savings.

Unless you mine bitcoin the remaining usage is mostly from running the stove or oven in the evening to cook dinner. Running your household lights, your fridge⁷, your TV, and your phone / laptop charger have a negligible impact on your true energy usage.

So, where we can, we use timers to run energy-intensive jobs during the day. For everything else we just get on with our lives and mostly ignore it.

One thing which will screw with this logic is the introduction of an EV to the house. We currently run two internal-combustion cars; inevitibly this will change over the next few years. If a car is only home during the evening, it isn't possible to charge from the sun. A household battery is one option here. Today that isn't financially feasible, but with the constant price reductions it may become realistic before we know it. That's a maths problem for Future Ross to deal with.

Costs and savings

The total we spent is $54,991. At face value it'll pay for itself in 21 years, which is about how long we intend to stay in the house.

Item	Cost
Retrofit Double Glazing	$28,174
Induction cooktop and electric oven	$7,387
Labour for cooktop (electrician + gas plumber)	$640
Heatpump hot water (supply and installation labour)	$5,643
9.8kw Rooftop Solar Generation System	$13,147
Total	$54,991
Total excl double glazing	$26,817

Our home already had a 63 amp connection to the street power supply which is enough to run the appliances we have installed. Some older homes seem to have 40 (or even 30?) amp supplies, which will definitely be maxxed out by all-electric homes. That would add to the cost for some homes. Thankfully not for us in this case.

Item	Annual Savings
Electricity savings *1	$1,834
Gas savings *2	$730
Comfort	?
Smugness	?
Annual savings	$2,564
Naive ROI *3	21 years
Naive Appliance-only ROI (excl glazing) *4	10.5 years

*1: Electricity savings based on solar generation; doesn't take into account efficiency gain from double glazing.

*2: Gas savings based on extrapolation of gas hot water usage and daily supply charges. Excludes savings from removal of cooktop.

*3: The ROI here is naive: it excludes inflation, interest, rising gas/electricity costs, or opportunity costs. However that means the real ROI is likely shorter. Sorry to my accountant father and my 7 years of economics and accounting lecturers for the laziness... it's getting late.

*4: I have included an ROI without double glazing here, to provide a comparison only focused on appliance replacement. This is obviously a much more appealing ROI but doesn’t truly reflect our personal investment here.

I'm very aware that this ROI is almost entirely made up of savings due to a large solar generation system. We see this as a single cohesive investment so I am happy to group these costs for ROI purposes.

There's also a non-financial saving: CO2 emissions. While it's technically possible to calculate pretty accurate figures here, even though this was an important side effect of our investment it wasn't a primary driver. As such I am rounding down our greenhouse gas emissions to "less than before" for this conversation.

The final factor that ROI should include is the impact on our capital growth. Since we're not selling our house tomorrow, and since it's impossible to truly understand the impact these improvements have had on our house value, I'm choosing to put my fingers in my ears, yell nyah nyah nyah nyah, and then just say it's increased the appeal and value of our house by approximately lots. Please, stop writing that complaint email right away... this isn't the reason we made these changes.

What if we went ahead with the new home we had planned to build?

It's hard to say exactly how much any of this would have changed for a new build. If we quickly review the decisions made above, we can pretty safely assume the incremental cost for a new build would be significantly less than it would have been to retrofit.

This is assuming you are electricity-only, which is now the baseline standard for homes in Victoria, and assuming you build to at least a 7-star standard which is also the legislated minimum for energy efficiency.

If I were to personally build today, I'd still incur the cooktop, hot water, and solar costs as they are above. I might save a few thousand dollars on the cooktop by uncoupling the oven and cooktop, but that's about it.

For solar, I'd likely scale up as much as possible so actually spend more on a new build.

It's possible to do this cheaper, for sure - by choosing cheaper appliances, using a resistive hot water instead of heat pump, and having a smaller solar system. This is just the way we decided to do this project.

What's next?

There are two key things we want to change to further our household's transition away from fossil fuels. Both involve huge boxes of lithum-ion batteries.

At some point in the next 12-18 months we're likely to replace one of our two cars; this will almost certainly be an EV. We're often able to juggle our car usage enough that we can do most (but not all) charging at home from solar, with a 'cost' of our feed-in-tarrif or less (i.e. $0.00 - $0.11c/kWh real cost).

This should also do a good job of using up our otherwise exported solar power, which is a better use case than exporting it to the grid for a pittance.

Lastly we'd love to add a household battery, however the economics of this don't add up today (Approx $14,000 for a Tesla Powerwall that won't save us enough imported electricity within it's usable life). Having an EV will dramatically change the need for a battery, so we need to re-run the numbers at that point in time.

A battery lets us grab any remaining solar generation, save it, and use it overnight. This reduces our exported solar but also reduces (or ideally removes entirely!) our electricity imports, making us almost grid-independent.

We'll keep an eye on both vehicle, and battery, costs over the coming years and add them into the mix as it makes sense.

Was it worth it?

Was it worth it? For us, yes it absolutely was. We love our home every day and regularly talk to each other about the particular bits that we're enjoying on that day. We get more joy than we should out of receiving an electricity bill for $0.36. We do intend to live here for 20 years so I am happy that we do break even - including the double glazing cost! Our position only grows stronger as energy prices continue to increase.

But is it worth it for you? Honestly, I can't say. Possibly not. And that's OK.

It's important that in Australia we move towards an electrified economy that doesn't rely on dirty natural gas or burning coal. Individual action only goes so far, but where we're able to help push for progress we should do it. Putting my money where my mouth is was an important way to send my own little message.

It shouldn't be forgotten that we were about to invest a very large amount of money building a house from scratch that incorporated the above technologies. For that, the incremental costs would have been lower than above (i.e we wouldn't have needed to remove a hot water system to install a new one). When that emotional investment is already made, spending the money on the same item in a different context becomes much easier to talk yourself into.

Similarly, I should call out that when we bought rather than built, we spent much less than we were intending to. This left us with a comfortable buffer to absorb these up-front costs.

The physical good feeling from a comfortable house is very valuable to us and we were prepared to pursue that outcome. The emotional good feeling from being free of natural gas, and having a low level of reliance on the dirty Australian power grid, is also very valuable to us.

I'm fortunate to be in a position where the sometimes eye-watering prices above felt reasonable. I don't take that for granted.

Discussion

I will talk - and have talked - about all of this to anybody who will listen. While I have no interest in debating policy or science, I love to talk about energy efficiency and both retrofitting and new homes. If you want help with decision making, or understanding what's worthwhile, reach out.

Community and other resources

I have learned a metric shitload about all of this from My Energy Efficient Electric Home (MEEH) - a huge Facebook community focused on electrification of homes and efficiency. The knowledge in that group is a very valuable source of information and discussion about all of the points I've covered here, and so much more.

Thanks to Tim Forcey for setting up MEEH and the broader community for the knowledge shared over the past few years.

For information on household energy efficiency, design principles, and detailed calculations for window size / eave projections / insulation / much much more, the Australian Government's Your Home website (and associated book) is invaluable. We used the book extensively during our house design process, and it was very helpful for our retrofit work.

Sustainability Victoria has quite a bit of information, in particular about heating and cooling.

I really liked this 99 Percent Invisible episode on gas stoves and our strong emotional ties to Cooking With Gas.

Sources

Where possible, I've linked external sources for e.g. the average power consumption of Australian households or for the historical dirty power usage.

The labour costs provided here are from the invoices we paid to third parties. Similarly, the costs provided for physical goods (the oven, solar system, etc) are from the invoices we paid. The price of "equivalent" induction and gas cooktops are today's prices from Appliances Online Australia, which is where we purchased our new cooktop.

The natural gas costs were taken directly from the bills we paid for ~70 days of service prior to the heat pump hot water install. This was a mid-winter to mid-spring period.

Electricty prices are taken from our actual electricity bills. Savings were calculated by Solar Analytics, which always has our up to date electricity costs along with our precise minute-by-minute generation/consumption/import/export.

Also? This entire post is full of opinion and if you don't like it, too late - it's my blog and you've just spent 20 minutes reading it. Sorry not sorry 🙃

Cover image: One of four banks of solar panels on our 2nd story roof. Photo by Ross Poulton.