The 70 % feed-in cap: what curtailment really costs your installation

“Solar panels: feed-in will often be limited to 70 %”. The sentence is accurate, and yet many owners took something else away from it: that a third of their production would go to waste. That is not what the rule says, and it is not what the grid operators applying it measure. Here is what the 70 % cap really does to an installation, with the figures.

What the rule actually says

The Electricity Act accepted at the ballot box in June 2024 came into force on 1 January 2026. Its article 17c, specified by article 19c of the ordinance, allows grid operators to limit the feed-in power of photovoltaic installations at the connection point. The value adopted by the industry is 70 % of the module capacity. The aim is to shave the midday peaks that saturate neighbourhood lines, so that more installations can be connected without reinforcing the grid.

Three points the headlines leave out:

• The law caps the loss: at most 3 % of annual production may be curtailed. If a fixed limitation cost more, the operator has to switch to a dynamic limitation, tied to voltage or remotely controlled.
• The rule applies to inverters installed from 2026. For existing installations, the industry recommendation is to apply it only when the inverter is replaced. Very small installations, under 800 W, and those above 1,200 metres are exempt.
• The energy that is not injected is not lost for everyone: it can be consumed on site or stored. The limitation applies to what leaves towards the grid, not to what the roof produces.

The loss caused this way is not compensated, the law says so explicitly. That is precisely why it caps it.

Why 30 % of power is not 30 % of energy

A solar installation reaches its nominal power only a few hours a year: perfectly clear sky, sun at its zenith, panels still cool. The rest of the time it produces at 20, 40 or 60 % of its capacity, in the morning, in the evening, under clouds, in winter, or simply on a hot July afternoon when the panels lose efficiency with temperature.

Plot the production of a fine summer day: a bell curve. The 70 % cap cuts off the top of that bell, a thin cap over the two or three strongest hours. The whole area under the line, that is the vast majority of the day’s energy, passes untouched. And on average days, the bell does not even reach the line.

That is why the measured loss is so small. Swissolar gives less than 3 % for a fixed limitation at 70 %, and the grid operators that have applied it since January observe less than 1 % of annual production in most cases.

In francs, on a single-family house

Take a 10 kWp installation in western Switzerland, producing around 10,000 kWh a year. The worst case allowed by law, 3 %, is 300 kWh. The curtailed energy is that of the midday peaks, so surplus that would have gone to the grid at the feed-in price, 6 centimes at the legal floor. The maximum shortfall is in the order of 18 francs a year, and in the usual case, under 1 % loss, a few francs. On an installation that saves several hundred francs a year through self-consumption, the cap does not show in the profitability calculation.

And that worst case assumes nothing absorbs the peak. A heat pump, a controlled hot water tank, a car plugged in at noon or a battery consume precisely the energy that would have been curtailed. Many inverters are in any case already sized below the module capacity, because that top of the bell never justified a bigger inverter.

What the limitation does not touch

• Your self-consumption. The limit applies at the connection point, after the house has helped itself. What you consume at noon is never curtailed.
• Your subsidies. The one-off remuneration is calculated on the installed module capacity, not on the injected power.
• The sizing. Nothing forces you to reduce your installation. On the contrary, an installation sized to the building’s consumption injects less at peak hours.

Two things to do, and one not to do

Ask the installer: how the limitation is implemented on your inverter, fixed setting or dynamic control, and whether an energy manager can steer the peak towards your appliances. That is one more line to read in a quote, just like the inverter warranty.

Watch: once the installation is running, the production curve of fine days shows a plateau at noon. That is the cap, not a fault. Monitoring your production lets you tell it apart from real underperformance, which shows other signs.

Not to do: give up the project, or undersize it, on the strength of a headline. Thirty percent less power for three hours on fine days is less than 3 % of energy over the year, and the law forbids going beyond that.

What decides the profitability of your roof is your consumption, your roof and the price of the installation. The free online study by SOLARSPLIT starts from those three inputs to estimate your production and your self-consumption, before putting installers in competition on an identical specification.