Negative power prices and solar panels on a large connection

What negative power prices, curtailing and the export limit do to solar panels on a large Dutch grid connection, calculated on 2025 quarter-hour data.

Why the price per quarter hour counts

A connection above 3x80 amps¹ could never net meter². The end of Dutch net metering (salderingsregeling) on 1 January 2027 therefore changes nothing here. What it means for a small connection is explained in the end of net metering in 2027 for businesses.

On a large connection, the contract states what exporting earns. If that compensation follows the day-ahead price, as in the worked example below, the value of solar power changes every quarter hour. On sunny afternoons the whole of the Netherlands generates solar power at the same time, and then that price is low or negative.

In 2025 the Dutch day-ahead price was negative for 585 hours, about 7% of the time³. Those hours fall in the middle of the day, exactly when the panels generate most: in 2024, 20% of all Dutch solar power already fell in an hour with a negative price³. Whoever exports at the day-ahead price then pays to get rid of the power.

Three things therefore decide what solar panels earn on a large connection.

• Self-consumption. A kWh you use yourself is one you do not buy. It is worth the power price plus energy tax, on a sunny afternoon too.
• The price at the moment of export, minus the supplier's discount. When that drops below zero, curtailing pays. For an installation of 200 kW or more per connection with SDE++ from 2023 or later, there is also no subsidy for power exported while the price is negative, counted per quarter hour since 1 October 2025⁴.
• The export limit. How much power you may export is fixed in the transport contract. In a congested area it can be less than the inverters deliver.

Worked example: a wholesaler with 400 kWp on the roof

A wholesaler has a warehouse with an office in the centre of the Netherlands. It is open on weekdays from 6:00 to 18:00 and on Saturday morning, and closed on Sundays and public holidays. The site runs lighting, packing and conveyor lines and a cold store, and the forklifts charge after closing time. The business uses 503 MWh a year, with a peak of 175 kW. On the flat roof are 400 kWp, east-west at 10 degrees, with 320 kW of inverters.

The business is an example: its consumption was built for this article quarter hour by quarter hour over 2025. The solar power was calculated from the weather KNMI measured in 2025, and the prices are the actual day-ahead prices of that year⁵. The roof produced 406 MWh, just over 1,000 kWh per kWp.

Buying costs the day-ahead price plus a €0.02 margin and €0.03868 energy tax per kWh⁶. Exporting earns the day-ahead price minus a €0.01 discount. Wattix calculated the year twice: with panels that always export, and with panels that curtail as soon as exporting costs money.

The difference in self-consumption comes from the lowest prices. Below −€59 per MWh the business gets paid to buy power even after energy tax, and then Wattix takes the power from the grid rather than from the roof.

Three things stand out.

• An exported kWh is worth little. A kWh used on site saved €0.12 of purchases on average. An exported kWh earned €0.06 with curtailing, and €0.01 without.
• Curtailing starts above zero. With a €0.01 discount, exporting already costs money once the day-ahead price drops below €10 per MWh. That is why Wattix curtailed 99 MWh, more than the 70 MWh that fell at a negative price. It saved about €2,300 a year.
• Weekends cost the most. 62% of the exports at a negative price fell on a Saturday, a Sunday or a public holiday, when the warehouse is mostly closed. On Sunday 11 May 2025 the price was negative from 9:00 to 18:00, down to −€350 per MWh. The roof exported 2,318 kWh that day, and that cost a net €308.

And the export limit? Say the business may export only 150 kW, less than half of what the inverters can deliver. Then Wattix curtails just 1.3 MWh more over 2025, about €45. The largest surpluses fall on sunny weekend days, when exporting already costs money: 90% of the power above 150 kW fell in a quarter hour below €10 per MWh. A low export limit need not break a business case. Whether that holds for another business depends on how consumption, output and price line up per quarter hour, and you only see that by calculating it.

“Before, we couldn't really back up our recommendations with a proper business case. With Wattix we can calculate multiple scenarios, compare the results side by side, and let the customer decide.”

Jesse Moms, Kremer Installatietechniek

What this means for the advice

On a large connection, annual totals say little. The example business uses more than the roof generates, and still exports 178 MWh, almost 40% of it at a negative price. What solar panels earn follows from how consumption, output and price line up per quarter hour. That is how you weigh the levers against each other.

1. Inverters that curtail as soon as exporting costs money.
2. Moving consumption to the sunny hours, such as charging the forklifts on weekday afternoons instead of in the evening. That does not help at weekends, when the warehouse is mostly closed.
3. A battery that keeps the surplus for later. How to size one is explained in sizing a battery for a business.
4. A different feed-in contract, for example with a fixed price instead of the day-ahead price.

What Wattix does here

Wattix calculates a year quarter hour by quarter hour with the Dutch day-ahead prices, negative ones included. Per contract you set the feed-in compensation and any feed-in costs, and per scenario whether the panels may curtail and how much you may export. That puts the levers above side by side and shows, per quarter hour, when exporting costs money. How to enter contracts is explained at compare energy contracts, and what Wattix does with solar power at use more of your own solar power.

If you do not know yet which contract the client will get, calculate several variants. What else a simulation calculates and how accurate it is, you can read in what an energy simulation is.

“You always have to make assumptions. But a platform like Wattix gives you the freedom to present results to your client in your own way, with the confidence that the underlying calculation model provides the same solid foundation every time.”

Fred Theunissen, De Installatiemakers