Mostly they have bad comments, and I know they are widely used in commercial applications, generally as an energy/cost saving where I sense they do work.
The domestic scene seems very different and energy / cost saving isn't my need. In my case, and possibly many others too, a problem exists.
AFAIK my 10kW solar array and two string inverters seem to push too much juice "up the spout" on a sunny day esp. with plenty of other arrays in the village doing the same thing, resulting in Local Grid over voltage.
Hitherto, this hasn't been a problem but I had a Zappi EV charger fitted which doesn't like these spikes and shuts down showing "Bad Voltage". This is annoying when you want to utilise the excess solar to charge the car. The obvious thing, I guess, would be to start switching on other loads in the home to try and increase the house load. Hence my interest in looking at any fixes to the system, VOs were the obvious.

I guess also that there may be settings on the inverters that could be tweaked causing a shut down in such spikes but that kinda defeats the object.

NB edit: perhaps there's a third way, by tripping the EV charger breaker leaving the Zappi off until required, maybe that would work albeit onerous.

There's a good thread at https://community.eonnext.com/threads/8546-Voltages-spikes-on-my-mains-power-exceeding-253-volts/ that seemingly explains the situation pretty well. TL;DR - talk to Zappi about loosening their over-voltage protection.

edit: There's also a page on my DNO's site that mentions EV chargers specifically https://www.ukpowernetworks.co.uk/voltage-changes-in-your-home-or-business

edit again: Perhaps also worth talking to your DNO if you establish that the spikes aren't your fault. How is your solar power regulated to conform with G.99 or whatever?

If there's local grid overvoltage(>253vac) then check if all the neighbours and your own PV installs are legit ie sub 3.68kw installs have been notified to the DNO and greater than 3.68kw have DNO consent, then get the DNO to sort out the problem.

Obviously if there's been little or no interaction with the DNO then the problem is likely to be found in everyones nearest mirror!

I have fitted voltage regulators in the past and they do seem to be reliable, but yes the advertised savings in electricity use are just marketing nonsense.

Any cost savings will result from the longer life of electrical appliances running at a consistent voltage within the range they are designed for.

Solar inverters do seem to last longer in combination with a VR.

In the early days of grid-connected PV (I started in 2001), we had many issues with variable grid voltage and mapped out areas in the country that have consistently higher grid voltage. Cambridge, Devon, North Norfolk all had shockingly high floating voltage (approaching 260 volts and spikes over 350 volts in worse cases).

Some areas were better than others, but if you lived in the sticks, at the end of a transmission line, or next to a heavy-duty industrial factory, you were likely to sit well above 253 volts. (Probably still are)

Quite a few customers complained that TV's, radios, microwaves, and toasters would only last a year or so in their house...

In those early days, we had to get dispensation from the DNO and SMA (inverters) to manually reset the Voltage range parameters outside the permitted range. It was a PITA (using power line modems) and sometimes took days of trial and error to achieve a working system. The DNOs really didn't care, as there were so few grid-connected PV systems in those days.

That changed with the introduction of FiT, and the DNOs 'should' have much better control of the voltages - if you suspect high voltages or continual spikes, in the first instance, you should contact your own DNO as Philedge advised.

You need to determine what the real problem is. High voltage or spikes?


Spikes are the cheapest to solve:

Back in the day, SPDs were horrifically expensive and only fitted for lightning protection of inverters in exposed locations. The one in my own consumer unit cost over £200 - got it free as a 'test' unit, otherwise I couldn't justify it.

Today, you can buy a DIN rail-mounted one (to fit in your CU) for about £17 (plus fitting). It's so cheap, I don't understand why they are not a standard fitting. Especially if you have expensive electronics in your house, like inverters and EV chargers. I believe EVs come with built-in SPD's but I'd still rather not risk that high-value item connected to the grid without an SPD on the house supply.


If it's high floating voltage, then get a VR. They are more expensive, but cheaper than the battery solutions suggested (which wouldn't solve the underlying problem in any case

Posted By: owlmanThis bore out the graph that Myenergi had sent me of one particular days Zappi voltage recording.

Have you been shown a graph showing what the Zappi sees when it shuts down?

Posted By: owlmanedit: it may be a result of long supply cable runs in rural areas and Network transformers at the limit of their capacity on those runs. I'm simply guessing.

We are at the end of a long run with years of low voltage, the DNO put the transformer up to the max to help us which meant that any up-tick caused those nearer the xformer to get over voltage. Sometime back the DNO gave us 3 phase (at their expense) to allow us to split our loads, this helped a bit. Eventually the DNO installed an additional xformer half way between us and the original xformer. Our voltage is now maintained within the legal limits.
(At one point our voltage would drop to 193ish when we had full loading).

I don't know if they can adjust the settings any more, I'll ask. I've a feeling they've tweaked them once already I'll check that too.

262 vac is the point at which our inverters have shut down in the past before grid upgrades that now hold it around the max of 253vàc on a sunny day.

AFAIK DNOs run the grid at as high a voltage as they can get away with to max the power they can transmit. Insulation will stand way more than that so there's negligible cost to operate that way. If they drop the voltage to 230vac where lots of people think it should be then they would have to increase the current to get the same power. That would need lots of bigger cables costing ££££££ so the higher voltage/lower current is the way they operate.

Maybe more power but used for a shorter period??? Same total energy???

And then there is the power factor that can also influence (confuse?) the issue.