Cheaper than free, to fill the car
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Beautiful spring day. Flowers soaking up the sun. Solar panels soaking up the sun, but I’ve switched the solar off. Why did I turn off free fuel for the car? There’s a cheaper option today than free. Say what?
There’s so much electricity in the grid, mainly from renewables, that the wholesale price has gone negative, so retailers are actually being paid to use it. Our retailer is Amber Electric, which passes on the wholesale price to us.
Right now, they’re paying us up to 9c per kWh to charge the car or run any appliances. Probably less than 5c per kWh on average, over the afternoon. Our house battery is “unfortunately” full from solar yesterday, so we can’t use it to soak up more of the cheaper than free electricity and get paid more.
Realistically, we’re not going to get rich from this. We might make a few dollars today. But getting paid a few dollars to refuel the car is better than paying $100 for petrol.
Charging
We returned home from a drive with 81% remaining car battery charge. As usual, we just plugged in when we parked in the garage.
If we allowed our solar panels to produce right now, it would have exported all to the grid, which the Amber app says would actually cost us up to 14c per kWh, during this reverse pricing period. Fortunately, the Amber app is smart enough to “curtail” the solar production from our Enphase solar panels, now that the electricity price is negative. But it’s apparently not smart enough to realise that when I plug in the car during reversed pricing, it should charge that from the grid. It starts the solar ramping up again. But, I want cheaper than free, dammit! So, I manually flicked the solar off at the control box (like a Neanderthal).
Frustratingly, Enphase seems to provide very little control for the owner to curtail solar. Amber has managed to find a way to turn off production or turn it on. But there’s no way to just tell it to not export. That means, for example, that when our system produces 9.6 kW solar, and the car takes 7.6 kW, it will still export 2 kW to the grid. It’s all or nothing, and won’t just lower production so export is zero. In some circumstances, I’ve actually switched our Tesla gateway to off-grid, as a workaround. But, I’m a nerd – most people wouldn’t care about this.
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- The other extreme: the night wholesale power went over $10 a kWh Why grid electricity is so expensive tonight 13 Jun 2025
- Our solar install day, with Enphase microinverters Solar-panel install day, with Lightning Energy 20 Dec 2023
Links
- Amber Electric, our retailer Amber Electric
- Enphase Energy, who make our solar microinverters Enphase Energy
Car , solar and battery
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Yes Amber does a negative FIT. I have EV, solar, and home battery. Yes sometimes I get a few cents back to my account. Based on your system setup, if you're in credit or pay less than $50/month, then this is great. Home battery could be an option to save extra cash
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Other wise manually turning breakers off
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