Welcome to OVESCO’s new monthly blog series on new innovations in renewable technology, and what they mean for you. The first article we have for you is from our Technical Director, Nick Rouse. It answers some common questions domestic solar owners ask about whether to purchase a new inverter or optimiser. There are many companies selling these products, some of whom make inaccurate claims. Here is OVESCO’s impartial view.


The inverter is the device that converts the DC electricity produced by the panels to AC electricity for use in the house. Among the suggestions sellers make of these products is that if the inverter is out of warrantee, you should replace it. You would not replace your electric kettle just because its warrantee has expired; there is no reason to replace your inverter if it is still working. Some sellers suggest that they may become dangerous if out of warrantee. Although inverters do occasionally fail, they nearly always fail in a safe way and merely stop working. To be approved for use in the first place inverters must incorporate a number of safety features that isolate them in the event of a fault. Some sellers even suggest that if an out of warrantee inverter causes a fire, the fire brigade will not attend or that it will invalidate your house insurance. This is utterly untrue.

The length of a warrantee is not a manufacturer’s estimate of when it expects the item to fail. It is the time over which the manufacturer expects that the overwhelming bulk of the items will operate faultlessly and not give rise to claims. I have an inverter at home with a three year warrantee which still works perfectly after fourteen years.

The only regular maintenance a solar system needs is a good clean. Even modest build-ups of dirt and bird droppings can seriously reduce their output. If you can do so safely, you can do it yourself. Extensions and angled jets are available for the pressure spays commonly used to clean cars. There is no risk to the panels, but be sure to be safe yourself. If you can’t safely reach your panels there are a number of firms that offer a specialist professional service. A normal domestic system should cost less than £50. If the panels are visibly dirty, you will recoup this cost quickly.


Sellers also suggest replacing the existing system with a more modern set up. In particular, one using ”optimisers”. Optimisers can indeed improve performance, especially at sites where there is some shadowing. However, the improvement is fairly modest at about 10% to 15%. While it is well worth considering them for a new system, the extra performance will almost never justify junking an existing working system. More worrying is that substantial modification of a system will disqualify it from receiving the feed-in tariff. Usually, you must certify that the system continues to operate as registered annually. Giving a false reply is an offence and admitting a substantial change risks disqualification. Like for like repairs are permitted, substantial changes are not.

Some sellers claim they work in conjunction with MCS, the Micro-generation Certification Scheme. They are not; MCS does not operate in this way.

If you or anyone you know is contacted, get in touch with us before you commit yourself. We can give you free independent technical advice on whether the proposed work is worth it. Do not be bamboozled into signing by such tactics as saying that this is a special offer that must be taken now or lost. Such ploys are warnings of a scam. Worthwhile offerings will be maintained and allow you to consider them at leisure.

Our verdict: If it’s not broke, don’t replace it with an expensive new one.