How big a problem is a (relatively) high home voltage?

June 9, 2015 9:49 AM

I have recently bought a flat (yay!). I had an electrician in today to look at some broken appliances (the hob, fridge and bathroom fan), and while checking things out he noticed that the voltage of the power in the house was unusually high (248-250V), possibly because I'm close to the transformer, and he confirmed that this could shorten the life of electrical devices. He mentioned that you can now buy a gadget to add to your electrics to step down the voltage to a more normal level, like ~220V. Is it true that a high-ish voltage can cause problems, and does anyone have any experience of the voltage-fixer he mentioned? I'm in the UK.
posted by Urtylug to Home & Garden (11 answers total)

If it were me, I'd call the power company first and ask them to address the problem with their product.
posted by Poldo at 9:54 AM on June 9, 2015 [1 favorite]

It appears the voltage standard for the UK is up to 253 (230V + 10%), so the power company is unlikely to do anything.

Things like fridges and fans will last longer if you lower the voltage, but the step-down transformer wastes energy and costs money to install, so I don't know if you'll end up saving money in the long-term.
posted by flimflam at 10:00 AM on June 9, 2015

I'd install a step-down even if the costs of premature failure of appliances and the transformer were equivalent because having to replace appliances and electronics frequently sounds like a frustrating pain in the backside.
posted by quince at 10:15 AM on June 9, 2015

The life shortening is how much exactly? The voltage is within spec, your electrician sounds like he is inventing jobs which need doing. Also note that voltage can vary and measured on another occasion may be different. Ask a neighbour if they have had problems, I doubt they will say yes.
posted by epo at 10:20 AM on June 9, 2015 [3 favorites]

Best answer: 250V is still within the regulatory limits of 230 V+10%−6% (253–216.2 V) and only 5% over the UK's standard of 240V so the power company is unlikely to do anything.

A 10% over voltage from nominal is both not unusual and unlikely IMO to have a significant impact on overall lifetimes. With a corrected voltage things like incandescent bulbs would last slightly longer (at lower lumen output). However uncorrected electric heat would work better and things with electrical motors might actually see a benefit from the higher voltage. Anything with a switching power supply is unlikely to affected at all.

Even a very high efficiency auto transformer is going to cost you at least %1 in transformer losses, probably more, which I would think would far outstrip any potentially shortened life time of connected equipment.

I would however buy a cheap digital multimeter and check my voltage in the the wee hours of the morning when loads are low (here you would just need to stick the leads into a socket, I don't know if that is feasible with UK style sockets). If you get readings out of the regulated range then I'd be raising hell with the power company.
posted by Mitheral at 10:31 AM on June 9, 2015 [3 favorites]

Best answer: The "normal" level in the UK has never been 220V. It used to be 240V, then was lowered to 230V for European harmonization (the rest of Europe used 220V, so they split the difference). Importantly, this harmonization just changed the published specs, not the actual voltage delivered to houses. By picking the allowed tolerance percentages carefully, all the 220V and 240V systems could call themselves "230V" without actually changing anything.

Wikipedia: Mains electricity standardisation.

248-250V shouldn't be a problem for old UK or new EU appliances and I sort of doubt the electric company will want to adjust it. But they might!
posted by ryanrs at 12:01 PM on June 9, 2015 [1 favorite]

Other side of the pond, but electrician installed a regulator in the fusebox that fixed this for me.
posted by Mr. Yuck at 1:43 PM on June 9, 2015

So, I live in a country that uses half the voltage of yours. The nominal voltage in your country is 230 or 240V; in mine, it's 115 or 120V. If I had 124-125V (the same overage by percent as you) coming out of the wall, I would not be concerned so long as it doesn't get much higher than that during off-hours, as Mitheral mentioned.
posted by Juffo-Wup at 7:42 PM on June 9, 2015

I agree with the others that you're not really out of spec. Plus, as Mitheral mentioned, you might want to get more than one reading, since it will probably fluctuate. My file server's APC UPS lets me graph the incoming voltage over time. I'm in the US so I think it should be 120 volts, but I regularly swing from 117 to 125 and have dipped as low as 107 (I hear the UPS kick in when it undervolts that low).
posted by Brian Puccio at 7:44 PM on June 9, 2015

I'm in Australia but we have the same voltage spec as you. Honestly this wouldn't concern me at all, when I was a technician I often had to know what voltage into a device was sitting at and it does vary all over the place. Measure again on a different day and you'll get something else.

I've never heard of anyone installing a step down for a whole house, that would be rather expensive and I think fairly pointless in this instance.

tl;dr - It's within both specification and normal range. Worry not.
posted by deadwax at 8:25 PM on June 9, 2015

Response by poster: Thanks everyone. After more measurements, the voltage appears to remain within the range referenced by Mitheral, so it looks like I'm fine.
posted by Urtylug at 4:55 AM on June 11, 2015