Reducing mains voltage to 220V to cut bills...

[colly0410]

In the local paper (Nottingham post) that a bloke called Corin Dalby says reducing the mains voltage to 220 volts (like in Europe) would reduce electric bills by 7% & no one would notice the difference. I remember the temporary voltage reductions they had in the early 1970's & the lights would be a bit dim & the black & white TV picture would shrink a bit. I'm wondering what effects a permanent 220 volts would have on electric gubbins in homes, & would it work to reduce bills?

[Refugee]

SMPSU driven kit uses less due to the ON resistance of the FETS being constant so switching a high voltage wastes less energy in the resistance as it is in series with the load.

[ppppenguin]

Although Refugee is technically correct this is a very minor effect. To a decent approximation, anyting with a switchmode PSU will use the same amount of electricty on any voltage within its range.

Lights will be dimmer and use less. You might or might not notice this.

Anything that makes heat as its main purpose will use less but take longer to do it. So boiling a kettle or making toast would take longer. Net effect just about zero. Charging an electric car may take less power but also take longer so no net effect.

Fans, vacuum cleaners etc will be slightly less powerful but you probably won't notice so a slight saving there.

Vintage kit would probably need to be set to a different tapping. A slight saving on AC/DC kit as less lost in the dropper.

Overall effect on bills? For most people it will be negligible.

[Murphyv310]

Hi
My take on this is SMPS will pull more current when the volts drop for a given load. This is the same on electric 13a vehicle chargers as far as I can see reading specs. As others have mentioned resistive loads like kettles will take longer to heat. Bear in mind that when the voltage was reduced in the 70s there was no SMPS in domestic applications. Some inductive motors that use run caps always run at the same RPM and with a fixed load will also draw more current with lower volts.
IMHO not a solution, best idea is to switch off appliances when not in use, remove chargers, unused clocks, lights, and anything that is unnecessary, I think we all should now know what to do.

[joebog1]

Being a really dumb transportee to straya,
I thort watts was watts?
lower voltage more amps = same watts just more heat and stress on insulation.
higher volts less amps= same watts but more heat and stress on insulation.

I am NOT shooting down the theory, just questioning basic sums, er I mean mathematics.

And in my 70th year, I have NEVER seen a method to reduce power thats required for a particular load!!.

Even if it does have swinging weights on the turntable.

PLAIN tungsten light bulbs perhaps yes, because its almost exclusivly resistive.
A heating radiator? a big coil of Nichrome wire on a ceramic former? yes, because essentially its a big resistor.

Joe

[ppppenguin]

Measuring the "vampire" load isn't easy. Most power meters aren't very accurate at the low end of the scale. No guarantee that they will get the power factor right either at very low loads. You pay for watts, but not for VARs. Modern chargers etc are meant to use much less than 1W when plugged in but not in use. Each watt is about £2.60 per year at current prices of about 30p/kWh. For older charges all bets are off. If it gets at all warm when not in use then it's using too much power.

You can't turn off fridges and freezers. A good fridge/freezer might use around 200kWh per year. So about £60 at today's prices. You also shouldn't turn off your modem/router. Perhaps 12-15W all the time, so 130kWh/yr, about £40. Beyond that most things can be turned off when not in use.

Useful guide, though not without errors: https://www.ovoenergy.com/guides/energy-...dby-energy

[Murphyv310]

Being a really dumb transportee to straya,
I thort watts was watts?
lower voltage more amps = same watts just more heat and stress on insulation.
higher volts less amps= same watts but more heat and stress on insulation.

I am NOT shooting down the theory, just questioning basic sums, er I mean mathematics.

And in my 70th year, I have NEVER seen a method to reduce power thats required for a particular load!!.

Even if it does have swinging weights on the turntable.

PLAIN tungsten light bulbs perhaps yes, because its almost exclusivly resistive.
A heating radiator? a big coil of Nichrome wire on a ceramic former? yes, because essentially its a big resistor.

Joe

Hi.
To an extent you are correct. A 2kw load at 20v will require 100 amps so the cross section of the feeder cable will have to be substantial due to resistive losses at 200v the same 2kv load takes 10 amps so you can use thinner cable, hence the high voltage power lines use relatively thin cable, if they carried 220v imagine what would have to be used!
Efficiency will reduce power usage, a radio with a dropper is inefficient as the dropper produces wasted heat, great in winter possibly but useless in summer temperatures, so either fit a transformer, diode dropper or capacitor, the diode being the worse option. Same with filament bulbs, replace with LED, there is more but I'd get boring.

[colly0410]

Seems to me he thought that as the difference between 240 & 220 is about 7% that electric gubbins would use 7% less electricity, as others have said kettles would take longer to boil, ovens take longer to get up to temp, electric fires/fan heaters wouldn't give out so much heat. Effect on bills? I suspect not a lot...

[joebog1]

Colly, ALL your examples are perfectly correct, AND also totally non inductive loads, or as I alluded to, purely resistive.
Check the motor specs on your egg nishners!!, I dont suppose many plebs have an air compressor, or lathe at home.
BUT they will chew more electricity as they consume more energy to make the same torque.
Watts are watts are watts. Power doesnt change, EXCEPT to convert it to another form, with anything other than resistors, it adds up.
Most of the arguments presented so far, totally ignore power factor, or phase shift/distortion.
The designers of power meters are VERY aware of the fact that power doesnt change, and incorporate measures to
MEASURE the losses " from normal " usage.

After all!!! we are the peasants, and they are the millionaires. ANY self respecting millionaire will spend at least half a million to recover 10 cents.
THATS why they are the rich, and we are the poor.
Its witten off on tax after all as " Business expenses to operate the company ".

With respect!!

Joe

[ppppenguin]

I did mention VARs and power factor. For most kit with poor PF, VARs will scale with watts as you change the voltage. Your electric meter meter measures watts and ignores VARs though this isn't true for larger non-domestic users who pay for VARs too.

VARs still mean current in the cables that heat them up and cause losses. VARs still have to be generated though to a first approximation they don't use any fuel to do this. VARs and harmonics are generally bad news for power distribution systems. For example 3rd harmonic causes high neutral current in a 3 phase system.

Although all modern SMPS are PF corrected (apart from the very smallest) they still make harmonics. I've put a scope* on a couple and it's not pretty.  The input current is in phase with the voltage but it's peaky. Some may be better than the ones I've tried.

Old fashioned radios and TVs with half-wave rectifiers were really bad offenders. They only took power during part of half of a cycle of mains. The waveform distortion could get serious in residential areas when lots of people were watching TV.

*You need to know what you're doing to do this safely.