Mains power voltage drop to reduce usage?

Instead of rolling blackouts when there's a power shortage, why don't we just allow (or deliberately) the voltage and frequency to drop? Wouldn't that make a lot of devices use less?

The UK is predicted to be 5% short this winter. Would a 10% drop in voltage cause problems? I doubt it since the legal rule is I get 230V+/-10% anyway, which is a 23V drop.

The other answers disagree, some loads would reduce, resistive heating for example (including washing machine heaters).

Note, since yourself and others keep dropping off the crossposts (idiots), you might not have seen the other replies, they're in alt.home.repair and uk.d-i-y

A device getting damaged by not enough power is screaming of bad design.

Recent research suggests "no" or perhaps not enough. At one time you could buy transformers to reduce the houshold voltage with the aim of reducing consumption. In the past where devices had conventional PSUs and we had incandescence lights this worked.

With modern devices it doesn't really work well. Many devices have switched mode PSU's which simply ramp up the input current to compensate for the lack of voltage so you don't save any power.

So TVs, computers, USB chargers and many LED lighting systems. Even a modern fridge has in effect a switched mode PSU so a variable frequency inverter drive to the motor.

That leaves devices which actually heat. Kettles simply take longer to boil, washing machines longer to heat up (they also have inverter driven motors, so again, essentially a switched mode PSU) so not much scope there.

Dave

What a ridiculous way to reduce power. Why not just turn less lights on, or use lower wattage bulbs? And turn the heating thermostat down instead of artificially throttling it?

Yes, but a lot of stuff would use less - washing machine water heater, electric water or house heating for example.

I've heard of that but never owned one, I doubt many have those yet. I assume a lower voltage would lower the consumption of most motors.

But it would make people use less at that precise moment. The problem is not overall usage, but peak demand.

Not necessarily. We have a "guaranteed" minimum and maximum supply voltage. Why should a company spend extra designing and installing protection against supplies (not temporary aberrations) outside them?

Because other things could cause lower voltage, like a wiring fault in the device or the building. Especially in dual voltage countries like the US where you can lose one live.

And all you need is thicker motor windings surely? Or a better cooling fan? Everything is designed to just manage to work, no safety margins like there used to be with "over engineering".

I recently broke a brand new strimmer simply by it jamming for precisely 1 second. Seriously? No thermal cutout? No over-current cutout? These devices are very simple and cheap to add. My £10 fan heater has a thermal cutout. It probably cost 50p.

The first two and possibly the latter have thermostats so will just be on for longer.

Even without that the motor would be on for longer as they have thermostats.

Actually my fridge freezer might as well not have one as it rarely turns off. Ice forms inside the fridge part and you can just about freeze vodka in an ice cube tray so it must be about -25C.

Yes, all sorts of issues if a power company messes around with the voltage and frequency. If a consumer wants to attempt saving money in this way then the obvious thing to try would be a variac. It won't change the frequency but does enable one to reduce the supply voltage easily to whatever device you wish to reduce the power to.

Have you measured how much that is costing you? Fridges are potentially a fairly major household power consumer these days now that lighting has become so much more efficient. You really don’t want a fridge that’s working harder than it needs to 24/7.

A power monitoring plug can be had for less than £15 and is a useful tool.

Tim

Those with switching supplies would compensate, taking more current, and eventually burning when the voltage goes below design margins. Otherwise, they would take the same power, so no gain.

Not the same thing at all. If you want to reduce usage, you turn things down or off. If the whole country wants to do that over a short period due to high demand, they can't very well phone everyone up and tell you to delay your coffee for half an hour, they have to lower the voltage.

Not the same thing at all. If you want to reduce usage, you turn things down or off. If the whole country wants to do that over a short period due to high demand, they can't very well phone everyone up and tell you to delay your coffee for half an hour, they have to lower the voltage.

But brownouts are to reduce current usage in a peak load, not overall throughout the day.

But brownouts are to reduce current usage in a peak load, not overall throughout the day.

They don't use those for heaters, only motors. Why would you need it for a resistive heater?

And they shouldn't burn they should cut out, a switching supply is quite intelligent.

Bullshit, a fridge or freezer uses 70W. F*ck all compared to total household usage. I'm currently using 8kW.

Wow, spending £15 to save £1.

I have a stupid fridge freezer which I can't adjust, it actually has only one thermostat! I either have the fridge frozen, or the freezer too warm. My LG fridge freezer is more sensible, the compressor cools the freezer, on command of the thermostat in the freezer part, and the fridge is cooled by a fan blowing air between them, on command of the fridge thermostat.