How long does an inverter last, and when to replace it

The inverter is the only part of a solar installation that really works: it converts the direct current from the panels into alternating current for the house and the grid, thousands of hours a year, while heating up. It is also the only part that will certainly be replaced over the life of the installation. Here is what you need to know so that day is neither a surprise nor a badly placed expense.

Ten to fifteen years, against thirty for the panels

A string inverter, a single unit on the wall of the utility room, is the standard for houses in Switzerland and lasts ten to fifteen years. Micro-inverters, one small inverter under each panel, are rated for twenty to twenty-five years because each one works little and stays cool, but the comparison is misleading: on a 25-panel installation that means 25 electronic devices on the roof, exposed to frost and heat, and replacing a single one means climbing onto the roof and removing a panel. They keep their place on a heavily shaded roof or one with several orientations, where they let each panel produce independently. For an ordinary roof, the string inverter remains the simple, accessible choice with the lowest maintenance cost, and it is the one installers propose first. The panels themselves still deliver 85 to 90 % of their initial output after twenty-five years. An installation planned for thirty years will therefore see one inverter replacement, sometimes two, and it is better to have it in the profitability calculation from the start.

What wears it out: heat first of all, an inverter placed in a poorly ventilated room or in full sun ages faster, then the electrolytic capacitors, which dry out with the years, and the daily cycles of starting and stopping.

The signs that announce the end

• Error codes and restarts that become more and more frequent, especially in hot weather. The inverter drops out, restarts, drops out. On the production curve, these are short, repeated zeros in the middle of the day.
• A falling yield: the curve keeps its shape but levels off lower than in previous years, in comparable weather.
• A noisy fan, or a silent one when it used to run, a smell of heat, a casing that is abnormally hot.
• Indicator lights or a screen that go off intermittently.

None of these signs can be seen from the window. They can be seen on the curve, and above all in the comparison with what the installation should produce. Our guide to reading your production curve describes the shapes, and SOLARSPLIT monitoring alerts you when the gap persists, whatever the make of the inverter.

What the warranty covers

Manufacturers guarantee the inverter for five to ten years depending on the make, and almost all offer an extension to fifteen or twenty years, to be taken out at purchase for a few hundred francs. On a new installation, the extension is generally a good calculation: it costs a fraction of a replacement and covers precisely the period when failure becomes likely. Check on the quote the warranty period and who carries it, the manufacturer or the installer, it is one of the points our guide to reading a solar quote recommends checking.

The warranty covers the equipment, rarely the labour for replacement or the call-out. And it never covers the production lost during the outage: that is the reason to monitor.

What replacement costs

For a single-family house, a new 5 to 10 kW inverter costs in the order of 1’500 to 3’000 francs installed, depending on capacity and make, more for a hybrid model capable of controlling a home battery. It is a maintenance expense, deductible from taxable income like other building maintenance work, and over thirty years it represents a few percent of the total cost of the installation.

The right time to rethink the installation

Replacement is the opportunity to take three decisions you did not have to take at the outset.

• The 70% feed-in limitation. It applies to inverters installed since 2026, and the industry recommendation is to apply it to existing installations at the time of replacement. The new inverter will therefore be set to curtail the midday peak, which costs less than 3% of annual energy, and often less than 1% when a heat pump or a car absorbs the peak. Our article on curtailment explains the mechanism, and it is the moment to ask for dynamic control rather than a fixed setting.
• The home battery. A hybrid inverter costs more than a simple inverter, but it avoids buying another one the day a home battery becomes worthwhile, with a heat pump or an electric car. Our guide on when a home battery is justified helps you decide.
• Monitoring. A new inverter is connected. It is the moment to activate monitoring that is independent of the make, so as not to relive the months of silent underproduction that often preceded the old one’s failure.

Do not wait for the June breakdown

An inverter that shows signs of fatigue in March gets replaced in April, not in July after three weeks of standstill in peak season. Installers have stock, the lead time is a few days to a few weeks, and a compared quote is worth as much here as for the initial installation. Production monitoring, to be activated from the Services page this way, is what lets you choose the moment instead of having it forced on you.