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Comment by thrdbndndn | Hacker News Reader

TIL UK (or EU) uses 230V, not 220V like my country.

The UK used to be nominally 240V and a lot of EU countries used to be 220V, but we harmonised on 230V because it's comfortably within the tolerance bands for both. Nothing really changed in practice - UK installations still deliver about 240V and most EU installations deliver about 220V - but it was convenient to have a common standard.

My UPS is showing 236V at the moment (continental EU). We also used to have 220V IIRC, but are now closer to 240V it seems.

My solar inverter consistently finds the UK grid at 243-245V.

UK actually uses 240V, which happens to be within +10% of 230V.

This is my favourite story about standardization.

It used to be the continent used 220V, and the UK used 240V, until we standardized on 230V.

The UK defines this as 230V -6% +10% (i.e. 216.2V – 253.0V), and nominal supply is 240V

The continent defines this as 230V -10% +6% (i.e. 207.0V - 243.8V), and nominal supply is 220 or 230 by region.

We called this harmonisation - in reality it's more like agreeing to disagree. We just fudged the tolerances until everyone was happy.

(To put some context around this - most sites don't receive nominal supply. The actual voltage delivered depends on your distance to the local substation. Typically they over-deliver such that sites closest are a little over, sites furthest are a little under. If they actually delivered ±0%, sites at the edge of their network would be further from nominal. So end-user equipment should be built to expect variation.)

230V±6% should be enough for both though, right?

That'd give an upper bound of 243.8, which is far too close to 240 to be practical. As I tried to add, there is some necessary and natural deviation from nominal to account for path loss etc. 230±6% only allows 240 to deviate by 1.5%, which isn't much scope at all.

I believe ±10% was the traditional definition, so they just trimmed a little off the top end so it strayed less from Europe's definition - but not enough to actually affect nominal distribution.

Po-ta-toe - po-ta-toh. You can use 220V stuff with 230V plugs. There are fluctuations for each network, anyway.

Which country are you talking about?

China.

In The Netherlands the allowed voltage tolerance is 10% by law. So everything between 207V and 253V should be fine. And we also had 220V until 1989.

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