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You might have read a post on Business Insider last month that told of a moment where the price of energy in the German electricity markets dipped below zero.

Last week, it happened in Queensland.

In Germany, it occurred due to a rare windy day which also happened to be sunny. The combination of wind and solar power entering the grid met nearly three-quarters of Germany’s total demand for an hour or so.

Because Germany’s grid is by law required to buy every kilowatt produced by renewable sources, it’s utilities were (excuse the pun) powerless to make any money as free supply outstripped paid demand.

Here’s how the same situation unfolded in Queensland on July 2, starting with this graph from reneweconomy.com:

Negative pricing does occur, but usually it’s around midnight and the early hours. You can see it nearly happened here on the morning of July 2.

It actually happened just after 2pm.

According to reneweconomy.com.au, it was a “combination of low demand and strong output from Queensland’s 1.1GW of rooftop solar”.

Queensland – the Sunshine State – has the lion’s share of solar output. More than 350,000 homes soak up that 1.1GW out of a total of 3.4GW across Australia.

July 2 was a perfect solar storm that hit coal-fired power providers in Queensland. It was a warm, sunny day, yet not hot enough for Queenslanders to be running airconditioners, and not cold enough for them to switch their heaters on.

The result was a blip that one trader told reneweconomy.com.au “he could not remember” having happened before.

Of course, it doesn’t mean that switching their lights and ovens on was free for Queenslanders during that magical 15-20 minutes. They still have to pay for network and retailer charges to have it delivered.

But for coal, according to The Guardian, those charges add up to 19c/kWh. Industry estimates put the same charges for solar between 12c/kWh to 18c/kWh, and forecast for under 10c/kWh in the not-too-distant future.

The point is, that for a moment last week, the coal power providers of Australia got a brief glimpse of what a widespread uptake of solar power in the suburbs can do to the price of energy in the right conditions.

And the larger the uptake, the less ideal the conditions have to be to have it happen again.

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