Cute thought, but it doesn’t work like that… the limit is the size of the breaker on the circuit, and if you want to pull 4.8kW from an outlet it’s pretty easy to install a 20A outlet. Nobody should EVER cross connect powerpoints. If your house is wired for 3-phase, you risk doing LOTS of damage to the wiring.
Easy when one pays a licensed electrician to install a separate 20A circuit and outlet or to connect the charger. There’s always a cost.
Gary1, thanks for raising the topic. I’m in QLD and right in the middle of investigating options for fast-charging a Mitsubishi Outlander PHEV that will arrive in November.
A number of people have mentioned the cost of three phase. Obviously every premises will be different. When we installed solar, about 18 months ago, we made a decision to rip out the existing switchboard and convert the house to three phase.
Including costs of our electrician for labour, switchboard replacement (including significant cost of complete cutover to Earth Leakage Circuit Breakers), upgrade to a board big enough to take 40 DIN units of breakers, replacement of the two underground feed wires with four underground wires, and the charges from the electricity supplier to cut us over from single to three phase, the three-phase project cost us around $2000. We thought that was a great investment in the future, and quite affordable as a component of what would come next.
Next the solar inverter was specified and implemented as three phase, and we’ve just added around 20kW of aircon (6kW power draw), at small incremental cost over single phase and significant benefit in terms of power handling. A three-phase car charger is next.
Note that an immediate benefit of three-phase is that we can push more than 5kW of solar generation into the grid. We routinely deliver above 8kW with the panels we have - 10kW at peak - and even at the pitiful 9c/kWh feed-in tariff we’re balancing out quite well.
What we really want to do is enable Vehicle to Grid, and have wiring that will allow us to run the house from the car overnight. From a regulatory perspective that’s only possible in SA right now, but I’m considering whether we can implement switching to allow us to completely isolate from the grid when it suits us. That’s an ongoing project.
The chances are that a lot of the capital investment we’re making will never be offset by whatever financial return comes from self-generated power. However we definitely feel good about the way we’re able to manage household opex, and the value we get from the solar panels. Ask me again next August when we’ve had a season of cooling, then heating, and 10 months of car charging. 
What you are describing is effectively an off grid system. That will require a different type of EV charger to implement conventionally. The switching and operation of your system will also need a technical appraisal to ensure the solution chosen meets the QLD connection rules.
The cost of Australian approved V2H or V2G chargers may be prohibitive. Compare that cost to the alternative of a small capacity home battery connected to your solar PV inverter. One able to power your home during the evening peak period.
We find that after around 9pm our power use drops significantly. Even in summer with the bedroom aircon running. It may provide a more flexible option for less cost without the need to implement a change over switching design. Consider also the lower night time cost of electricity on a Time of Use tariff or Solar Soaker plan. The average savings over night on our usage would be less than $1 per day (1-2kWh consumption over 10 hrs).
Consider the more one self consumes the less electricity exported. Feedin credits become less valuable possibly not even covering the fixed daily connection charge. If the payback on the capital investment is not important, and only the daily running costs, would one be better to go off grid and use the EV as backup when needed. It’s a divergent discussion.
Is there a point at which the QLD connection rules and prospects of future cost increases/changes will open up more owners of EV’s to seek alternatives to grid connection? Independence considered more valuable relative to the investment required.
P.S. Mitsubishi news release related to it’s V2G options.
Not quite - I’m foreshadowing a self-managed hybrid arrangement that complies with a regulatory regime, as opposed to the hands-off system that I’d really like to have in place.
…and that’s true. I’m in discussion right now, and - even if the hardware is available - it’s likely to be 10x the cost of a three-phase on-grid car charger. Annoying.
Our consumption rises a bit from sunset until bedtime, but we know exactly why. We have a high-tech environment with an atypical amount of technology. The house uses around 450W overnight, 750-1000W in the evening, and variable amounts during the day.
How do we know this? One of the best investments we made along the way was the network-connected smart-meter integrated with the solar system. The incremental installed cost of the meter along with three years of expanded reporting was about $350. I can’t recommend that highly enough as an investment. It was worth the cost just for amusement value, and it’s definitely telling us about our power habits, so at least some of the cost is offset by changes in our behaviour.
Just by interpreting the online metering graphs we can identify when the hot water is recovering, when someone has boiled water, what the air-con consumes, how long an iron was running, and more. We’re making surprisingly granular interpretations of power use, and we’ve changed our habits accordingly to maximise self-consumption. And when I borrowed a loaner car to test drive, we could see exactly what it consumed from the grid on recharge - so I’m heavily motivated to charge it from self-generated solar.
And this is where it gets interesting. After spending $85k on a car that has 20kW of battery and can run the house if allowed, do I want to spend another $20-30k for equivalent additional capacity (batteries plus implementation) that still won’t actually deliver the same outcome as the batteries I have in the car? And assuming I’m allowed to do it, there’s significant benefit in being able to isolate from the grid: if the grid goes down, the house doesn’t. Right now if the grid goes down I could be generating 10kW of solar and the house will turn off to protect the grid. Absolutely understandable for a simplistic system, and compliant with how the regulations work, but not at all helpful.
Again true, but only if you don’t actually want to consume the electricity you generate. Under all circumstances using the power you generate is better value than feeding it into the grid. Yes, by not feeding power to the grid you forego revenue or cost-offset. But the whole point is to use solar to offset the 3-4 times cost of running the household from the grid, and self-generated power - whether live or from a battery - is the cheapest way to do that.
By the way, what an excellent thread. Thanks to everyone who has chipped in information. It’s very just-in-time.
Positive feedback is always welcome. It’s worth noting the current topic is focussed on the issues specific to connecting EV chargers to the grid in Queensland. Useful for others to share different strategies to work within the current rules.
For a more appropriate and broader discussion of home Solar PV with battery storage or EV charging, etc note the following topics.
‘Home Electric Vehicle Chargers - #10 by Mpainesyd
‘Solar and Grid Connections - #96 by grahroll
‘Solar Feed-in Tariffs - #71 by person
‘Solar batteries - #38 by PhilT
‘Home battery storage (solar systems) - #191 by PhilT
There are more readily found using the search tool (magnifier symbol) near the top right hand corner of each Community web page.
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