Temporarily shutting off your solar panels when electricity prices are negative
With all the solar panels and wind turbines that have been installed in the Netherlands in the past years, the grid sometimes gets saturated with all this weather-related clean electricity. The result is that spot prices for electricity come tumbling down at those moments of high supply. High supply and weak demand can even cause the power prices to drop below zero at times.
Negative power prices: what does it mean?
If the spot price for power turns negative, it means that you would basically get paid for consuming power, instead of having to pay like you normally would. For some people, this is a reason to switch from a fixed energy contract (with fixed prices per kilowatt hour), to a “dynamic” energy contract, with prices that change hourly and are based on market prices for electricity.
Turning off solar panels as a solution
People with a dynamic energy contract AND solar panels on the roof have one more reason to watch out for negative electricity prices. Because if there's a negative price for the purchase of electricity, then there's a negative price for electricity feed-in as well: it means that for every kWh you let flow back to the grid, you would then have to pay money, instead of receiving money for it. Of course nobody wants that, so many people are saying: when the price drops below zero, I'll just switch off my solar panels. Problem solved, right?
If the electricity price turns negative, then it makes sense to turn off the solar panels for a while. But note that it's the 'all-in' price that needs to be negative for it to make sense, not just the net trading price on the electricity market. The “all-in” price for electricity is equal to the net price plus taxes and levies. The additional amount that comes on top of the net price is around 15 to 18 cents. That means that only when the net price for power falls below minus 15 to 18 cents per kWh, it starts to make sense to switch off your solar panels.
Even if the 'all-in' price is only just above zero, there is no point in turning off the solar panels. The net metering mechanism ensures that each kWh fed back into the grid is worth exactly as much as what you have to pay for it; therefore, as long as the all-in electricity price is above zero, the feed-in price is too. So it still makes sense to let the panels produce electricity at that moment.
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When does it make sense to turn off your solar panels?
If the electricity price turns negative, then it makes sense to turn off the solar panels for a while. But note that it's the 'all-in' price that needs to be negative for it to make sense, not just the net trading price on the electricity market. The “all-in” price for electricity is equal to the net price plus taxes and levies. The additional amount that comes on top of the net price is around 15 to 18 cents. That means that only when the net price for power falls below minus 15 to 18 cents per kWh, it starts to make sense to switch off your solar panels.
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And when doesn't it make sense?
Even if the 'all-in' price is only just above zero, there is no point in turning off the solar panels. The net metering mechanism ensures that each kWh fed back into the grid is worth exactly as much as what you have to pay for it; therefore, as long as the all-in electricity price is above zero, the feed-in price is too. So it still makes sense to let the panels produce electricity at that moment.
The picture above shows, on the left, the net power prices for April 13, 2024. Between 11 a.m. and 5 p.m., the prices are negative. But if you set the slider at the top right to 'show all-in price', it shows that in fact, at no time during the day, there were really any negative purchase prices, so no reason to shut off your solar panels.
It doesn't happen often that we have dynamic electricity tariffs that are so low that it is worth turning your solar panels off. But in any case it's good to know how to turn off the solar panels safely. Switching them off is always done via the inverter: if the inverter is off, the panels do not generate any power. You can turn off the inverter manually if you are home.
For SMA inverters, it's best to turn off the inverter on the AC side. If there is an AC switch mounted near the inverter, as shown in the picture, you can turn it off. Otherwise, you can switch off the circuit breaker for the solar panels on distribution board.
SolarEdge inverters can be turned off by pushing the pin located at the bottom left of the device from position 1 to position 0.
Can solar panels also be turned off remotely?
A remote shut off of the system is possible in some cases, but not all. Here's a list of options.
SolarEdge systems can automatically stop working based on the dynamic electricity prices. It's a feature that you can activate using the 'MySolarEdge' app. This video on Youtube explains how it works. When you select the option, don't forget to enter the additional costs per kWh (i.e. the difference between the net price and the all-in price)!
If there's a Sunny Home Manager in your system, then you can't turn the panels off completely, but you can set the feed-in power to zero. In that case, power will still be produced by the solar panels, but only as much as is currently being consumed in the house. If there are batteries installed, any surplus power will go to the batteries. That means there is no feed-in to the grid. To do this in the classic Sunny Portal, go to “Configuration” and then to “PV System Properties” and click on the “Parameters” tab. Scroll all the way to the bottom and click on 'Edit'. Under the heading 'Limiting of the active power feed-in' you can then set the feed-in to 0 kW (or to 0%). Remember to click 'save' at the bottom of the page. Of course, when the power price becomes positive again, don't forget to undo the above! On EnnexOS you'll find the settings under 'Configuration' and then 'Grid management service'.
SMA inverters that communicate on the EnnexOS platform can be turned off remotely, but only by someone with the role of 'administrator'. This works by logging into the ennexOS portal and clicking the cog wheel icon on the left for the 'configuration' menu. Then click on 'Device Parameter Adjustment'. A blue button appears with the text 'System parameter assistant': click on it. You will now enter a three-step menu. In the first step, you select the inverter. In the second step, you will see a list of parameters. Type 'operating mode' in the search bar. Now the 'General Operating mode' appears, which is set to the value 'start' or 'MPP'. You can change this value from 'start' to 'stop'. By clicking 'continue', followed by 'Save', the new value is adopted: the inverter switches off.
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Systems with SolarEdge inverters
SolarEdge systems can automatically stop working based on the dynamic electricity prices. It's a feature that you can activate using the 'MySolarEdge' app. This video on Youtube explains how it works. When you select the option, don't forget to enter the additional costs per kWh (i.e. the difference between the net price and the all-in price)!
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SMA systems with a Sunny Home Manager
If there's a Sunny Home Manager in your system, then you can't turn the panels off completely, but you can set the feed-in power to zero. In that case, power will still be produced by the solar panels, but only as much as is currently being consumed in the house. If there are batteries installed, any surplus power will go to the batteries. That means there is no feed-in to the grid. To do this in the classic Sunny Portal, go to “Configuration” and then to “PV System Properties” and click on the “Parameters” tab. Scroll all the way to the bottom and click on 'Edit'. Under the heading 'Limiting of the active power feed-in' you can then set the feed-in to 0 kW (or to 0%). Remember to click 'save' at the bottom of the page. Of course, when the power price becomes positive again, don't forget to undo the above! On EnnexOS you'll find the settings under 'Configuration' and then 'Grid management service'.
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SMA systems on the EnnexOS platform
SMA inverters that communicate on the EnnexOS platform can be turned off remotely, but only by someone with the role of 'administrator'. This works by logging into the ennexOS portal and clicking the cog wheel icon on the left for the 'configuration' menu. Then click on 'Device Parameter Adjustment'. A blue button appears with the text 'System parameter assistant': click on it. You will now enter a three-step menu. In the first step, you select the inverter. In the second step, you will see a list of parameters. Type 'operating mode' in the search bar. Now the 'General Operating mode' appears, which is set to the value 'start' or 'MPP'. You can change this value from 'start' to 'stop'. By clicking 'continue', followed by 'Save', the new value is adopted: the inverter switches off.
At the risk of : it will only rarely be worthwhile to really switch off inverters - only when the “all-in” price really drops below zero. That really only rarely happens: this year, for example, so far not at all! But it is nice to know what is possible. There are new developments all the time; when there is news again, we will be sure to let you know!
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