by Chris Woodford. Last updated: February 28, 2020.
Do you ever hear people talking about using a sledgehammer to crack a nut? Using
too much force where only a little would do is obviously a waste of
energy—but it's something we all do, all the time, where
electricity is concerned.
Broadly speaking, voltage is the electrical equivalent of force and we
often power electrical appliances and gadgets with far more volts
than they actually need. Using an "electric sledgehammer" to
crack an electrical nut wastes money as well as energy and can dramatically
shorten the life of expensive equipment. If you're running something
like a factory with lots of huge machines powered by
electric motors, using
too much voltage might be adding an unnecessary 10–20 percent to your
electricity bill; multiply that across the whole of the industrial
world and you get a big problem that's bad for the economy and bad
for the planet. One solution is to use voltage optimization
equipment (also known as voltage correction, stabilization, regulation, or reduction), which constantly regulates your electricity supply so you get precisely the voltage you need. Let's take a closer look at how it works!
Photo: The concept of voltage optimization: it converts power-line waves of different shapes and sizes
into ones of just the right shape and size to run your equipment more efficiently.
Why voltage can be a problem
Ever noticed that all the little gadgets and gizmos you have around the
house use slightly different voltages of electricity? Your big appliances
are all designed to run off the household supply, typically 110 volts or 230 volts depending
on where in the world you are. But the smaller gadgets will use
all kinds of different voltages. A flashlight will use about 3 volts, a digital
camera 4 volts, a cellphone or CD player 6 volts, a laptop about 20 volts, and so on.
Ever wondered why bigger appliances need more?
Think voltage, think force: broadly speaking, you need a bigger
voltage to force an electric current through something like the electric motor in
a refrigerator or a vacuum cleaner than through the tiny little filament lamp in a flashlight or the microchips in your laptop. You
need a bigger sledgehammer to crack a bigger nut.
Another way of thinking about this is to remember that the amount of power
something electrical uses is proportional to its voltage. If you need
an electrical appliance to make your life easy by doing something
that requires lots of energy (like trimming your hedge or tumble-drying your jeans), it's also going to need lots of energy putting into it each second—and
that means plenty of voltage. In theory, you could power a tumble dryer with a 1.5-volt battery, but its tiny voltage would produce energy much too slowly to evaporate the water from your clothes and such a puny power pack simply doesn't contain enough energy to do the whole job. A 110-volt (or 220-volt) dryer will do the job properly and much faster, but it won't necessarily make any difference if your household power is actually 130 volts (or 250 volts)
Photo: Power plants are designed to produce reasonably constant voltages with voltage regulators, ammeters, wattmeters, synchroscopes (which keep power generators in sync with one another and
the power grid they're connecting to), and much more. Photo of power regulating equipment in a control room at White River Hydroelectric Project by Jet Lowe, courtesy of US Library of Congress, Prints & Photographs Division, Historic American Engineering Record.
Once electricity leaves a power plant, utility companies have little or no idea what we're actually doing with it. They just give us all the same basic supply
and let us get on with it. In practice, industrial users will get
much higher voltage supplies than homes so they can drive powerful
factory machines but, even so, there is only a relatively crude link
between the voltage that's supplied and the voltages we actually
use. The mismatch between these two things can be a big problem and
a huge waste of energy and money.
Most electrical machines are made and sold internationally and have to
work on different voltages in different countries. An electric lathe
(factory cutting machine) might be manufactured in Germany to work right across Europe (a huge
swathe of the world) on voltages ranging from 200–250 volts: in
Germany, it'll happily work on 230 volts; in the UK, it'll work just
the same (no faster or better) on a national supply that's sometimes closer to 240
volts—but the higher voltage will make it waste about 10 percent
more energy by getting considerably hotter (potentially reducing its
useful life quite significantly). If you're using that machine in the
UK, you might wish your electricity supply were 230 volts instead of
240. This problem is often referred to as overvoltage.
Chart: Voltages around the world: As all travellers know, electricity supply voltages vary around the world, though generally there are just two common bands: roughly 100–130 volts for North America and the Pacific and 220–240 volts elsewhere. That's obviously a problem for manufacturers who want to make products for the global market, but less of a problem in a single continent, such as Europe, where voltages have been standardized. Source:
Mains electricity by country (double-checked with a second source).
Transients and harmonics
There are some other issues to worry about too. The voltage your building
receives can rise and fall quite dramatically from hour to hour (even
from minute to minute or second to second) due to fluctuations in
demand and supply. If a factory is turning big electric machines on
and off in your neighborhood, for example, that can lead to
transients (brief spikes) in power that can affect
other buildings nearby. Spikes (sometimes called surges) and sags (sometimes called dips)
can also be caused by lightning strikes, power generating equipment going on- or offline,
and lots of people all using electricity at once (cooking at
the same time each evening, for example). In practice, a supply that
is supposed to be 230 volts could be fluctuating regularly by as much
as 10 percent or more, giving you an actual voltage anywhere from
about 210–250 volts.
And it's not just the voltage that can vary. In theory, most electricity is supplied as an alternating current (AC)
sine wave, which rises, falls, and reverses direction smoothly something like 50-60 times a second (the ordinary
supply frequency). In practice, AC supplies can also include irregular,
higher-frequency waveforms called harmonics that
potentially damage delicate equipment (by causing overheating) and really need to be filtered
Photo: Ideally, alternating current should vary smoothly in this up-and-down sine-wave pattern. In practice, it can change more drastically and erratically, harming your equipment.
How bad is the problem?
As householders, we don't mind all this too much; most of us aren't even
aware of the problem. Like me, you're probably used to having lots of
little gadgets (laptops, cellphones,
electric toothbrushes, and so
on) all with built-in transformers that convert the ordinary power
supply (nominally ~110–120 volts in North America and the Pacific region
and ~220–240 volts in Europe and elsewhere) to the correct voltage in
each case (15 volts for the laptop I'm typing on, for example). And maybe you have
surge protectors fitted to a few key appliances (like your computer
or your wireless router) to safeguard against spikes and lightning
If you're running a business, the mismatch between the voltage you're supplied with
and the voltage you need is much more of an issue: it's costing you a great deal of money you don't actually need to spend.
Photo: Electronic household gadgets that use low voltages typically have small transformers built into their power cords. These all run off the European power supply of 230 volts or so, but actually supply much smaller voltages to the appliances they power. Clockwise from the top: transformers for a modem (18 volts), a cellphone charger (5.9 volts), and an iPod charger (12 volts).
How does voltage optimization work?
There are two main ways to solve the problem. The first is to have your own,
simple step-down transformer (also called a voltage-reducing
or "tap-down" transformer) to change a higher incoming voltage to a
lower level more in line with what you actually need. Factories and
offices with their own dedicated substation or transformer effectively
have this option already; they can simply readjust what's called the
"tap setting" (the ratio between the incoming and outgoing
voltage) so their transformer supplies a lower voltage than before.
Alternatively, an extra step-down transformer can be added to reduce the
voltage from the outside electricity supply to one that more closely
matches what's needed by the building's internal electricity system.
The trouble with this approach is that it solves only the problem of
overvoltage. If you're sometimes getting too little voltage
from the supply (a problem also called "undervoltage" or "brownout"), altering the tap setting to
reduce overvoltage will make matters worse.
Photo: A step-down transformer like this one (which is supplying my electricity as I type this) reduces the high-voltage power from electricity cables into a lower voltage for homes and factories. Adjusting the tap settings will make it produce a higher or lower output voltage from the same input voltage.
A better solution is to use dedicated voltage optimization equipment that
constantly adjusts the voltage from the supply, either increasing or
decreasing it so it remains within a narrowly defined band. Devices
that do this are called voltage regulators, voltage
optimizers, voltage stabilizers, or voltage correctors. They need no maintenance or monitoring and work happily for
many years without replacement. They also filter out spikes and harmonics to give a smoother power supply all
“Defra (The UK Department of Environment, Food, and Rural Affairs) has... [used] voltage optimisation... to deliver a carbon saving equivalent to 25 percent of our carbon reduction target. It will cost £1.8 million with a payback in less than two years through energy cost savings.”
Defra, Departmental Report, 2007
Voltage regulators can work in a variety of different ways. Some are based on ferroresonant transformers
(also called constant voltage transformers or CVTs), which are like ordinary transformers but with an extra component (an inductor, based on a capacitor and resonating coil built into their secondary winding).
Normally the primary (the "input") and secondary (the "output") of a transformer are coupled so any changes to the
primary voltage are directly reflected in the secondary: if the primary voltage rises, the magnetic flux induced in the
core of the transformer rises and the secondary voltage rises too by a corresponding amount. The extra circuitry
in a ferroresonant transformer keeps the magnetic flux of the secondary section of the transformer at a constant and maximum value, whatever happens to the flux in the primary. That ensures the transformer gives a more or less constant output voltage (usually fluctuating by 1-3 percent) even if the input voltage varies slightly.
Other voltage regulators work a different way. The simplest ones are essentially
electronic. They work by constantly measuring the voltage of
the waves that make up the incoming electricity supply and comparing them with the
voltage you say you want. If there is too much voltage, they add a second wave of just the
right size, in antiphase with the original, to subtract exactly the right amount of voltage.
So if your incoming supply rises to 250 volts and you'd set the regulator to 220 volts, it
will add an upside down waveform equivalent to 30 volts to the 250 volts, subtracting just
enough power to make 220 volts. If the supply dips to 240 volts,
the corrective voltage will immediately dip to 20 volts, keeping the output steady at 220 volts.
A voltage regulator is usually a more expensive solution than a simple
step-down transformer, but it can save half as much energy again,
giving overall energy savings of 10-20 percent. Although large units cost thousands
of dollars or pounds, typically, they pay for themselves in 2-3 years
(in lower energy and maintenance costs and by extending the life of
the electrical equipment they're connected to). They also have a
payback for the planet: by cutting your energy consumption, they're
helping you make a positive contribution to tackling environmental
problems such as climate change.
Photo: You might think all your household electrical appliances are running off a 110-volt or 220-240-volt supply,
but many of them secretly transform that voltage to something else without your knowing. A little circuit like this is built into the base of modern energy-saving fluorescent lamps (also called compact fluorescents or CFLs). It boosts the frequency of the supply so the lamp can be small, bright, and compact and so it doesn't flicker.
Voltage optimization at home
Voltage optimization equipment is sophisticated and used to be beyond the budget of all but big businesses and industry. But small, vastly scaled-down versions of the same basic equipment are now being mass-produced for ordinary householders. One small voltage optimization gadget, manufactured by VPhase, promised to reduce household electricity supply from 240-250 volts (potentially fluctuating from 200-250 volts) to a more consistent level around, say, 220 volts, offering a potential saving of 10 percent on electricity bills. Smaller voltage optimization units typically don't protect against transients and harmonics, however
and they have been criticized by consumer group Which? for costing too much and taking too long to pay for themselves.
Ultimately, there are simpler, cheaper, and quicker ways of reducing your household energy bills, some of which
(like turning down your thermostats very slightly) don't cost anything at all.
What is the catch?
Same output, lower input—voltage optimization sounds too good to be true. Indeed, it
sounds like it violates one of the most basic laws of physics: the conservation of energy.
According to that law, you can't make energy out of thin air or get more energy out of something
than you put in. So if you reduce the energy going into an appliance, aren't you going to get less energy
out? Or, to put it another way, if voltage optimization lowers the voltage, doesn't it make something
like an industrial motor slower and less effective? Won't it make something like a refrigerator
or an air conditioner less effective at cooling? Won't it make your lights dimmer?
The answer is sometimes yes, sometimes no. Remember overvoltage,
which we introduced above? If you supply something like a motor with more voltage than it needs, it doesn't spin any faster: it just
wastes the extra energy as heat. Reduce the voltage and you reduce that wasted heat before you reduce the useful
energy that turns the motor. In other words, if you run the motor at its ideal, lower voltage, you make it more efficient. The energy you save in this way is energy you're not drawing from the power supply, so it translates into a financial saving (for you) and an environmental benefit (for the planet). It's worth remembering that if you run appliances with too much voltage or current, they'll wear out significantly more quickly. Extending the lives of electrical appliances also translates into financial and environmental benefits.
Now it's worth pointing out that if you cut the voltage too much, you are bound to reduce
the output of whatever appliance you're powering: the conservation of energy tells us that
must be the case. Consider an extreme example and this
is intuitively obvious: you cannot run a 220-volt domestic refrigerator with a 1.5-volt battery, simply because a
battery with that low a voltage can't supply enough energy to power a motor that big. In other words, there is a limit to how much you can cut voltage without cutting useful output.
So what is the limit? Some manufacturers of voltage optimization equipment
claim that our everyday voltages are perhaps 10–20 percent too high for the appliances we use,
which suggests you can safely cut the voltage you supply by perhaps 10–20 percent without sacrificing any useful output from an appliance.
This is misleading. The reality is much less clear-cut and depends on what kind of appliances you're supplying, how they're loaded, and how
much you try to reduce the voltage. It's certainly possible to save energy and money with voltage optimization,
but you might well reduce the effectiveness of whatever you're powering at the same time.
Will the lights get dimmer with voltage optimization? For many types of lights, there is a roughly linear relationship between
the voltage you supply and the light they produce (luminous output); reduce one and you are bound to reduce the other. Think of how a
simple flashlight (torch) bulb gradually gets dimmer as the battery loses its charge. What's actually happening (though it's not
obvious) is that the battery is slowly losing its voltage (typically from about 1.5 volts, when new, to around 0.5–1.0 volts when it no longer does anything useful) and the lower voltage means less light. Interestingly, for some types of lights,
there is also an inverse linear relationship between voltage and lamp life, so the lower the voltage, the longer the light lasts.
Now maybe your lights will be a bit dimmer with voltage optimization—and maybe that doesn't matter if your building was too bright to start with or the potential cost savings (through lower power bills and longer-lasting lamps) are more important to you.