Replacing an inverter: when and what to look for?

Solar panels are tough: they often last 25 years or more and still deliver a large proportion of their original output after that. An inverter is a different story. It contains electronics that run hot day in and day out, and those wear out faster. On average an inverter lasts 10 to 15 years. Some go longer, others give up after just eight years. It is therefore not a question of whether you will ever replace it, but when.

That difference in lifespan is worth knowing if your system has already been on the roof for a few years. If you have panels from the early days of the solar boom, say around 2012 to 2015, your inverter is now approaching the end of its technical life. That is not a disaster: your panels are still fine, and you simply connect a new inverter to them. It helps most if you see it coming, so you are not suddenly without output for weeks.

The location of the inverter also plays a role. If it hangs on a warm loft in full sun, it runs hotter and wears out faster than an inverter in a cool, ventilated spot. Heat is the biggest enemy of electronics. When replacing, that is the moment to look at whether it can hang better, so the new one lasts longer.

The clearest sign is an error code or a red light on the inverter itself. Most inverters have a green light when everything is running well; if that turns orange or red, or a code appears on the display, something is wrong. Sometimes it is a temporary notification that goes away by itself, but if it keeps coming back or stays, it is time to have it looked at.

More often you notice it through the output. If your system is suddenly generating much less than you are used to on a sunny day, or the output drops away entirely, that points towards the inverter. Many people only notice it on the annual bill or in the app, when there is a big gap in production. Keep an eye on your output and you will pick up such a drop earlier, without standing still for months without noticing.

Complete failure and error notifications in the associated app are also among the signs. If the inverter does nothing at all, keeps giving the same fault, or you receive notifications on your phone that the connection or production has dropped away, that is a sign the end is approaching. Sometimes a reset or a small repair is enough, but with an inverter that is running towards 12 to 15 years, replacing is usually wiser than continuing to repair.

The most common is the string inverter. There your panels are connected in series (a string) to a central inverter, usually in the meter cabinet, on the loft or in the garage. That is a proven, affordable solution that works fine for most roofs. The downside: if a panel is in shade or dirty, that drags down the output of the whole string. For a roof without much shade that is rarely a problem.

Micro-inverters work differently: they sit under each panel separately, on the roof. Each panel converts its own current independently of the rest. If a panel is in shade or not performing, the others keep running at full power. Handy with roofs that have shade, dormers or panels in multiple orientations. They are slightly more expensive and sit on the roof, making replacement more involved, but if one fails no more than one panel goes down.

The hybrid inverter is the newer addition. It can not only convert the power from your panels but also manage a home battery: charging during the day with your surplus and discharging in the evening or when there is little sun. That way you use more of your own solar power yourself. If you do not have a battery yet but are thinking about it, a hybrid inverter keeps that door open without having to redo everything later.

The most important thing is that the power rating of the new inverter matches your panels. An inverter that is too small cuts off the peak of your output on sunny days; one that is far too generous runs inefficiently and costs unnecessary money. A good installer works out the number of panels and the peak power and chooses an inverter that matches. If there is still room on your roof to expand later, you can factor that in now.

Also look carefully at the warranty. A new inverter usually comes with a manufacturer's warranty of five to ten years, sometimes with the option to extend it for an additional payment. That is worth comparing, because electronics are exactly the component that wears out first. Also ask what the installer themselves guarantees on the work. With us you get a warranty on the installation, so the connection is as good as the device itself.

Finally, pay attention to the monitoring. Almost every modern inverter has an app or portal showing your output per day, month and year, plus notifications in the event of a fault. That is not just nice to follow: it also means you see a future drop immediately, rather than only on the annual bill. Make sure the monitoring actually works and is set up on your phone at handover, so your system reports to you from then on.

If your inverter needs replacing anyway, this is the moment to think ahead. If you are toying with the idea of getting a home battery one day, you can fit a hybrid inverter now that is ready for it. If you choose an ordinary inverter and the battery comes later, you often have to buy a new inverter again or fit a separate battery inverter alongside. Choosing hybrid straight away saves you that double step.

That is particularly interesting now that net metering is changing. As you get progressively less back for power you feed to the grid, it becomes more attractive to use your own solar power yourself rather than giving it away during the day. A battery, managed by a hybrid inverter, stores your surplus for the evening. Whether it pays off for you depends on your consumption and the prices, so work out the sums calmly before you buy the battery.

At the same time, not everyone needs to go that route. If a battery is genuinely not on the cards for you, with a hybrid inverter you are paying for capabilities you will never use. Then a good ordinary inverter is perfectly fine. If you are unsure, have an installer think along about your consumption and your plans. We explain honestly what makes sense in your situation, without talking you into something you do not need.