What if told you there was a petrol station selling half-price petrol?
Forget the dollar figure, just imagine the traffic chaos and thousands of manhours wasted queuing.
Read on and we’ll explain how to get cheap fuel dispensed with zero effort from the convenience of your own driveway… it’s an absolute no brainer.
Of Course We’re Talking About Electric Vehicles
They’re perhaps more accurately described as storage with a steering wheel, transport appliances or passenger batteries.
No matter which way you look at it, EVs are large batteries, they allow you to store free energy AND eliminate your petrol bills.
While compliant, warranted and well-installed home batteries cost around $1000/kWh, a 39kWh Nissan Leaf can be had for $35,000… the battery is cheaper, and you get a free car!
Plus, there’s the fact petrol is hellishly expensive compared to grid electricity as a motor fuel.
In this complex graph we see real time, self consumed solar in yellow, with almost all the solar energy available captured. The bright green is yield stored in a house battery, and purple represents charge to fuel an EV. In both cases these batteries are charged by “smart solar” that follows the inverter output without importing any energy. Only once both these vessels are full of sunshine, does the grey area show export of excess energy to the grid.
Is The Fuel Really Free?
Well yes, more or less. It can depend on how ruthless you are in counting beans but we’ll explore a few figures here using a rough average of 15kWh consumption for 100km travelled.
- A reasonably efficient car burns petrol at 10 litres/100km. By the time that fuel has been shipped halfway across the world it is $1.85/litre. 10 x 1.85 means the fossil industry has consumers well-conditioned to pay $18.50/100km.
- The most expensive electricity dispensed at highway fast chargers can be up to 80c/kWh. However Evie Networks provides very fast 350kW DC charging at 65c per kWh. Highway food might be bad and expensive but road trips are now much cheaper. 15 x 65c equates to $9.75/100km.
- Some slower EV chargers are used as loss leaders to attract customers to a winery for instance. Others like Jolt offer your first 7kWh for free, which is more than half a tank of fuel in my adorably modest EV. However, in traditionally expensive South Australia I’ve recently paid 25c/kWh. So CBD parking may still be a ripoff but charging while you’re at work isn’t. 15 x 25c equates to $3.75/100km.
- If you’re very lucky there are retailers paying 12c/kWh for energy you export to the grid. Forgoing this credit on your account means you “pay” 12c/kWh for storing energy. So at worst, home charging from solar is still less than a tenth of the cost of petrol. 15 x 12c equates to $1.80/100km.
- If you live in Victoria your retailer may be particularly scummy and only offer the mandated minimum 0.04c per kWh. At this point solar yield is almost free energy. 15 x 0.04c equates to 6cents/100km.
What About Sunk Costs?
If you invest $1 per watt installed, or $10,000 on a 10kW system, it should yield around 40kWh/day. Over 20 years that yield will have cost about 3½ cents/kWh, which considering inflation, is a lovely steady number.
- So it’s not unreasonable to say home grown energy to fuel your transport needs is 3½c/kWh. 15 x 3.5c equates to 52½cents/100km.
I’m not about to calculate the opportunity cost of missing a perfect ponzi, crypto, stock market investment where I could have better invested my money using 20:20 hindsight, personally I’ve got more interesting grass to watch growing.
However, if you’ve installed a 10kW solar power system which has a fixed 5kW export limit, your yield can be wasted by curtailment.
This is the worst kind of waste, where you’ve paid the money but the energy simply cannot flow to anywhere useful.
If we assume the worst case where your bell curve of potential is reduced to an Uluru of practical execution, there could be 13% of the energy you have paid for up front simply not coming to fruition.
While it’s raining down on your roof, curtailment sees energy pour down the drain. Using storage means you’ve captured truly FREE energy.
To start, the simple way to explain what I call a sunshine circuit is simply to turn on a load when your solar has ramped up to a certain yield. Solar diversion is the common terminology, because you take electricty destined for export to the grid and divert it into your own storage or consumption.
Storing Solar Energy Will Save You Thousands
They say planting trees is best done 20 years ago, so you’d best start digging today.
As batteries are many times cheaper now than they were 20 years ago, storing solar electricity is increasingly viable economically.
We aren’t talking about seasonal duration, like a tank of heating oil or a tonne of wood for your combustion stove. Rather it’s a shift in mindset, a matter of gathering fresh energy every day and using it over the next night or two.
Here we see light blue turns to purple once the battery (represented by the pink line) is full. The major consumption of stored energy runs 6pm till 9:30pm. Next day we do it again.
It’s Time We Got Smart
When there’s abundant sunshine, then really, there’s no problem. Having lots of electricity available is a feature, “wasting” it with mid-summer curtailment is not a bug.
What we need is clever ways to generate and store energy when conditions aren’t so generous.
That’s why efficiency will always be king, especially in a long overcast week of winter. Insulation, double glazing, thermal mass, automation & clever design will pay huge dividends economically.
What’s harder for the accountants to quantify though, is comfort. Going home to a place you find relaxing improves outlook, lifts productivity & lowers anxiety.
As does slashing your electricity and fuel bills, in any case. To turn your home into a giant storehouse of free sunshine read our guides on solar panels, batteries and EV chargers.
Note: the original version of this article wrongly described Victoria’s minimum mandated FiT as four tenths of a cent, when it is actually 0.04c, not 0.4c. Apologies, and thanks to Les in the comments for the correction.
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yeah,
but the problem is the greedy state governments looking to replace lost fuel excise and making lots of noise about a per km fee for electric cars, which, if truly replacing lost fuel excise, is going to run you about 80c a km travelled. This will far exceed the cost of power for charging your battery even at the most expensive price you mention.
That will make EV’s far less attractive.
Putting a battery on your house is still far better bang for your buck than an EV. Mind you as you say, buying the EV and putting it on blocks to act as a large battery might prove quite cost effective, whilst but buying one and running it down the road wont be saving you a lot.
Great article couldn’t agree more and v2g or v2h will be a game changer !!
The solar batteries make more and more sense. I understand the Electricity prices will increase with 9% from 1st July (Qld Southeast) and not to mention that the Solar export was recently reduced down to 4 c/KW.
Do you really want to export and get paid 4 c and to buy back electricity at over 35 c?
And yes 35 c is cheaper than $ 1.80 per L petrol..if you have a charger at home but even 65 c seems to be a bargain
And yes, the battery price have come down but still $ 1,000 per KW..not many people can fork this amount of money upfront..Just food for thought..
“If you live in Victoria your retailer may be particularly scummy and only offer the mandated minimum four tenths of a cent per kWh.”
Anthony, I read of this Vic proposed 0.04 of a cent feed in sometime ago, likely here on solarquotes.
That is actually 4/100 of a cent.
I thought it might be an actual typo ow way they presented the figures in para 2 here . . .
https://www.esc.vic.gov.au/media-centre/regulator-releases-draft-decision-solar-minimum-feed-tariffs-2025-26
But when they later say down from 3.3c, you know they really do mean 0.04 of 1c, ie 4/100th of a cent.
Now this is the proposed minimum, it remains just how many retailers would be willing to push that button first.
But if one or two jump on it, the rest will likely follow.
Goes to show FITs are going to be gone everywhere in the coming year or two, and how important using and storing as much production possible has become.
Fixed – thanks for catching this Les.
We opted for a Powerwall 2 about 3 years ago, when having solar installed, and many friends thought it was a crazy decision, not ‘cost-effective’. But at the time, and it’s proven to be have been a good call, what appealed to me as much as storing solar-generated excess was also being able to make use of cheap or even free grid rates, as well as protect against climate-driven outages (the number of which grow every year in my area).
Now the battery is the most interesting part of the whole home energy system. We have 3 energy sources, solar, supercheap (8c/kW) grid power and free grid power. I don’t even use peak grid, the battery has allowed us to avoid it pretty much all year. At first I used Tesla’s excellent app to manage the automation of the multi-component system (which also includes an EV), but now I find NetZero’s built-in automations are by far the most useful and powerful.
Have you done an article on NetZero’s automation options? They’re superb (I think). Can avoid using any battery storage for EV charging, set a whole smorgasbord of conditional chanrging and discharging options etc.
Hi Anthony, I agree with the logic of your article and it is in the same line of my thinking to proceed. I do have a 15 kW solar system tith a 19 kWh battery. We running on the hot days here in victoria up to 12 at night the AC to cooldown the house and the battery is not drained by the next morning even if we use the heat pump to boost the hot water for the morning showers. Similar to your system, graphs above, at around 10:00 to 11:00 the battery is fully charged for the next cycle.
The stats that I saw quote about 20 kWh for 100 km but it most probably depend on what car you have. I am looking at the HAVAL from GWM. It have a 34 kWh battery and they claim 180 km range, it is a HYBRID.
My problem now is the winter here in Victoria, I am sure that there will not be enough sunshine to charge the battery. There is not enough wind around to install a wind charger and I am not interested in a generator. I am thinking very hard for en energy solution outside the grid. Perhaps thermal?
Solar to charge EV is great is retired or WFH, but if you commute to work, then you’re not plugged in during solar peak. A short commute might be covered by a home battery, but that’s a big investment for limited ROI. There was an attempt to be able to send code with packets of electricity, so in theory you could plug in anywhere and withdraw a proportion of the power you send to the grid (not the actual electrons generated), but a form of trading at some nominal fee – while technically possible, it was a bureaucratic nightmare.
Hi,
For those who commute to work there is a simple solution. Many familes nowadays are two car families. If both cars are electic, then you drive each of them to work on alternate days. The day that a car is not being driven it can stay home and recharge. The car that is at home recharging can still be used to go shopping, or for emergencies, which is usually only a short trip, if need be, or the car that was driven to work can also be used to go shopping on the way home.
Hi,
I have a Nissan Leaf e+ and would absolutely love to have V2H. Unfortunately, it doesn’t look like it’s ever going to happen. Finding the necessary hardware is proving extremely difficult.
So if someone knows of any, that doesn’t involve also spending money on an unnecessary Lithium ion battery, then please let me know.
Ideally it would be a DC coupled hybrid inverter.
(Quasar wallbox 1 is no longer available, and IMO was too expensive anyway.)