Electricity

I guess that it might be useful to start with some basics because most of my clients – and if I am honest me too – have a wee bit of in-built resistance (forgive the pun) to all things to do with Electricity – it is dangerous, it comes in funny boxes with wires and contactors and signs that tell us we are in mortal danger and so – quite rightly – we leave it to the experts – the Electrical Contractors / Engineers and largely we remain in the dark (unless they are doing their job of course!)

So, first things first, the main thing you are looking to reduce on your electricity bills is the number of kWh (kilowatt hours) as this is a direct measure of the energy you have consumed and so this is what your supplier charges you for – yes there are other charges and I will go into these later but first let’s look at energy consumption.

kWh are made up of two things:

  • kW and hours – simple I know but this is important
  • kW represents your Power Demand and this is a function of voltage:
  • kW = Voltage2 / Resistance
  • also kW = Amps x Voltage

kWh are simply the number of hours that the kW load has operated, so for example, if you have a 250W lo-bay down-lighter and it runs for 4 hours it will – nominally – be attributable for 1kWh of electricity consumption.  A simple picture but essential in grasping the basics of your electricity costs. Voltage – guess the only thing you need to know about here is whether or not the loads you are using in your business are Voltage Dependent or not.

Let’s look at a simple example, a 40W GLS lamp is a voltage dependent load, so if it is supplied with the design voltage of 230V it will consume 40W – but if it is supplied with 242V it will draw over 44W which is 10% extra power for no more light output.

So, too much voltage costs you money on your voltage dependent loads.

Voltage indepenent loads are those which have a fixed supply voltage, for example a laptop which might have a fixed output power supply unit that gives 20V at any supply voltage.

Another example would be a simple electric kettle which is a resistive load – the fact that the element is thermostatically controlled means it is basically voltage independent.  In fact if the voltage is high the kettle will boil more quickly although it will still take the same amount of energy to boil the water as it would at a lower voltage!  Is all this clear?

If this isn’t clear email me with your queries

Now the picture gets a wee bit more complicated when we go back to the 250W lo-bay mentioned above because nominal power consumption and actual power consumption can be very different and discharge lighting – like 250W SON Lo-Bay for example suffer from ballast losses that can be as much as 40% of nominal power draw.  General rule of thumb – the older and dirtier the lo-bay fitting the more the ballast losses.

Now we get into Power Factor – and as this is a very complex picture that most of you won’t care about I have given this a page unto itself. Fill Yer Boots.

What Can I Do?

One of the first things to look at is switching off unecessary loads.  This sounds so simple that of course everyone should be doing it but in practice it isn’t quite so easy. Just ask my teenage kids who seem physically incapable of turning anything off once they have finished with it! Drives me to distraction. Leaving a room to me means also switching off the lights – assuming I am the last one out of course!

Parasitic loads or Vampire loads as I call them when talking to kids about energy exist in any building.  They are things like TVs left on standby, mobile phone chargers left ON when the phone is fully charged, computers left ON all night with the printer, scanner, external drive, etc all powered ON and in many cases the monitor ON with a screen saver running – here’s a simple maxim – Screen Savers Save Screens – They Don’t Save Energy!!!!

Automatic Controls

There are a vast array of automatic controls on the market in case your fingers do not work – here are just a few ideas of what might prove useful in your business.

Office Equipment

Here is where you can get involved on a day to day basis in making a difference.  How much can I really save I hear you say (in my head anyway!)

Photocopiers – power can be saved when the standby mode is engaged during operational hours – the unit is actually unplugged “out of hours” because of you leave it plugged in but switched off it still uses 2W an hour.

Computers – as with copiers we have energy being consumed in sdtandby but also – importantly – when switched off but still plugged in – so unplug them if you can – or use “intelliplugs”.
When your computer is “off” but plugged in still consumes 5W an hour.  In standby, that is, still switched ON it is using 25W an hour.

Monitors –  when you leave a monitor to turn itself off – which most of them do now automatiucally – but you leave the wee green /red or amber light ON you are wasting about 8W an hour so lets assume you leave your monitor in this condition every night of the year – you have just wasted 35kW!  Please actually switch it off at the mains.

Printers – these only actually need to be turned on to print something.  In standby (switched ON) a Laserjet will consume around 18W an hour reducing to 2W when you switch it off but don’t unplug it!  18W an hour for 12 hours for 365 days = 79kW wasted every year.

Coffee Machines – the number of times I come across these babies left ON all night beggars belief – the picture below is from a well-known tourist attraction in Edinburgh that shall remain nameless – lets look at the facts.  This is attached to a machine with a 3kW electric heating element that heats water in a very well insulated storage vessel so that users can get a piping hot coffee at the press of a button (or pull of a lever).  When the cafe is not working, which is 14 hours a day – every day – the storage vessel loses heat by radiation and conduction to colder parts of the machine and the manufacturers tell me that as a result the heating element cycles approx. 40% of the time to maintain the stored vessel at just shy of boiling point.

So, for 40% of 14 hours a day a 3kW element heats up consuming 0.4 x 14 x 3kW = 16.8kW x 365 days = 6,132kWh/year at a cost of £582.54.

This was truly a no-brainer.  I have now removed the offending sticker!

Coffee Machine

Parasitic loads like this really stack up – particularly when you then add in things like phone chargers, hand held tool chargers, vending machines, illuminated displays………………

As the Carbon Trust poster tells us – Switching Off Non-Essential Equipment In An Office Overnight Saves Enough Energy To Run A Small Car For 100 Miles!