When I was a kid growing up in Yorkshire, wasting electricity was almost criminal. Coming from a place synonymous with frugality, I learned early that every kilowatt-hour was sacred. And fair enough: back in the 1970s, generating each kWh of electricity meant burning roughly a kilogram of coal mined by Arthur Scargill’s finest1.
Fast-forward to today and things couldn’t be more different. Solar and wind have free ‘fuel,’ and we often find ourselves with more electricity from wind and solar than we know what to do with.
The solution: curtailment, the practice of intentionally limiting renewable energy output when there’s too much.
Curtailment means we’re well on our way from energy scarcity to energy abundance. And counterintuitively it is not a sign to slow down or stop building more renewable generation.
Continuing to build more solar and wind capacity, which will only increase curtailment, isn’t wasteful; it’s strategic. It ensures our future electricity mix is cheap, clean, and abundant most of the time.
Renewables Are Already Dominant
To give this some substance, consider the work of renewables expert David Osmond, who runs simple weekly simulations2 of Australia’s main electricity grid using scaled-up amounts of solar and wind generation and real demand data. His findings show Australia can get close to 100% renewable electricity using 120GWh of storage (about 5 hours at average demand). His most recent results indicate that:
- Last week his simulation of Australia’s main electricity grid achieved 99.7% renewable electricity, despite demand being well above average, and wind being below average.
- Over the last 186 weeks, the simulated grid averaged 98.7% renewables, with about 16% of wind and solar generation regularly requiring curtailment.
David Osmond’s latest simulation of Australia’s main electricity grid.
How Curtailment Affects Homeowners
For homeowners with recently installed solar, curtailment can mean dealing with flexible exports, when your solar inverter’s exported power is remotely throttled to manage grid stability (but still producing enough solar to power your home).
I get it: it hurts seeing that beautiful solar curve squashed down on your monitoring app, not to mention losing out on feed-in tariffs (FiTs). But here’s the thing: if you crunch the numbers, at current FiT rates (~5 cents per kWh or less), the dollar loss is small relative to savings from self-consumption of solar.3
Some might still see curtailment as wasteful, but that’s old-school thinking. What really matters now is timing. A kilowatt-hour at 6pm on a cold, still winter evening is precious. But at midday on a spring day, electricity can be so plentiful some customers literally get paid to use it.
The challenge today is balancing abundant daytime energy with storage like batteries and pumped hydro, occasionally supported by gas peakers. This optimal mix lets us rely on renewables without fear during those tricky evening peaks.
Next time you hear complaints about curtailment being wasteful, remember it’s proof we’re on the right track, building enough renewable energy to make Australia’s energy mix plentiful, cheap, and clean. Curtailment isn’t just cool — it’s essential.
Footnotes
- I’m assuming 1970’s UK coal plants were half the efficiency of a modern Australian black coal plant ↩
- Yes – this is a very simplified model of the grid, and we’ll need more than just more generation and storage – but it is all doable if we are motivated ↩
- It would, however, take the sting out if more retailers offered higher FiTs in the late afternoon, rewarding savvy homeowners with big west-facing arrays who contribute power precisely when it’s most valuable. ↩
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It is OK to just switch off our connection to the grid, but cutting off our solar panels completely when we could be charging the car is really annoying.
Hi Mel,
It’s only very basic backstop control or critical emergency where inverters would be turned off completely.
SAPN are running flexible exports where a grid event would see *exports* throttled to zero at worst.
You can still use your own power.
Curtailment means there is a lack of storage pumped hydro is probably the way to go for longer duration storage many many suitable sites and best of all pump’s generation equipment and also earth works can be done using Australian materials and labour helping balance of trade independence and national energy security.
Curtailment, backstop, I’ve seen another term used in one state, but can’t recall that right now.
Yes, it will become more and more necessary to curtail more often, the more household PV, commercial / industrial rooftop, and large solar / wind farms, get more renewables into the grid.
Here in SA, SAPN have curtailed 2 or 3 times only since flexible exports began some years ago (2020 ?), and the annual test to make sure it’s working, for about an hour at most.
Their written policy is to curtail large solar / wind ops first, then larger commercial / industrial rooftop, then lastly residential rooftop.
“Curtailment means we’re well on our way from energy scarcity to energy abundance.”
Only of we can store it, and use it in non solar hours early morning and evening.
This is vital for residential, as it can make homes with suitable PV size and battery capacity totally independent for grid needs, and have enough to contribute to peak demand times . . . it needs to be a VPP type thing, with excess to a households need put back into the grid when needed in the peak demand, perhaps in exchange for subsidy contribution to get a battery and installation.
Commercial and industry rooftop can also be used if they don’t require battery power after normal business hours, as a VPP type arrangement almost all of their battery excess could be used similarly to assist peak demand times.
There’s a long way to go with that, but experimenting is taking place with trails like the SAPN / ARENA / AGL Solar Grid Savers plan starting May, and they have done a couple of these in the recent past few years here too.
I feel one issue is that some people think curtailment means the inverter is turned off, & their own requirements are fed from the grid. This is incorrect as modern inverters can be throttled back to reduce the grid feed, but self consumption of excess is allowed.
A better way to look at this is thinking of a variable feed in allowance. Many systems are already curtailed due to the Export limit (Rural NSW 3kw/phase in some areas, 5Kw/phase most common). If curtailment is merely seen as a temporary tightening of the export limit, it is less frightening. Also, the daytime grid voltage is often high, so the inverter cannot push much excess to the grid anyway.
Remember: Perception! Perception Perception!. The Media fear-mongering about curtailment is a far larger problem than the actual curtailment.
However, I think energy resellers should be asked to assist customers to better use their self consumption & batteries, if fitted. These retailers should get a report about curtailment, so can pass that information to the consumer.
Absolutely agree, if you have a battery you can also make some real cash with a controller at the other end of the spectrum to help the grid when there is a lack of energy https://www.smartmotion.life/product/solar-and-battery-controller/
Your figures of 99.7% & 98.7% are misleading unless you include other information. 99.7% is not so impressive if it was for 5 mins at midday.
I find that very hard to believe, looking at the open electricity data for Queensland for last week, at no time did Coal drop below 40% of the power mix in use. It never does.
Hi Andrew,
Aside from rooftop solar, Queensland is a bit backward in renewables but they’re making progress.
Have you heard about South Australia recently?
Now running a rolling average of 70% renewable over the last 12 months. 80% over summer.
South Australia has just chalked up what is undoubtedly a world first – a run of more than 10 consecutive days over which the average production of wind and solar accounted for 100 per cent of local demand.
No other gigawatt scale grid in the world has come close to this amount of “variable renewable energy”, or for such a long time.
https://reneweconomy.com.au/south-australias-remarkable-100-per-cent-renewables-run-extends-to-over-10-days/
“South Australia set an impressive new renewable energy record in the final days of 2021, with the state’s solar and wind farms and rooftop solar systems supplying an average of just over 100% of local demand every day for a period of almost one week.
https://reneweconomy.com.au/south-australia-winds-up-2021-with-smashing-new-renewables-record/
Net exporting interstate via two interconnections (soon to be three) into Victoria two years running. The world’s first Gigawatt scale grid to have ever been run solely on rooftop solar.
https://reneweconomy.wpengine.com/wind-and-batteries-saved-the-day-when-storm-cut-south-australia-adrift-22060/
https://reneweconomy.com.au/world-first-south-australia-achieves-100pct-solar-and-lowest-prices-in-australia/
https://opennem.org.au/energy/sa1/?range=1y&interval=1M
Like Queensland, VIctoria is also nowhere near having enogh renewables to meet demand. Low prices and curtailment here require two things: lots of solar AND coal generation that cannot or will not turn off. When the coal goes, we will be able to use much more renewables.
David
How do those graphs relate to graphs on apps such as NEM Data and PocketNem, which show that across Australia, coal and gas still dominate the supply by fuel type?
As the post says, it’s “a simple weekly simulation of Australia’s main electricity grid using scaled-up amounts of solar and wind generation and real demand data”. Follow the link in the post for more details of the simulation’s assumptions etc.