How much power do I need?

How much power do I need?

Whatever event you are putting on, a party, a wedding, a market, or even a festival you will likely have some requirement for electricity.  Working out how much you need is fundamental, ringing up or emailing a power provider and saying “I’m putting on a party and I’ve got a band and some food for the guests, can you supply a generator?” generally leads to a sinking feeling amongst us electricians!

What we need to know is how much power is needed, how many sockets, what type of sockets and where it is needed.  Without this information we have two choices, guessing with the risk of everything turning off or supplying far more than is needed increasing costs.

At home we take it for granted that we can plug an appliance in and there will be enough electricity to run it.  There are several reasons for this – firstly we have an amazing national grid to supply our electricity, dating back to the 1920s and secondly there was some very clever design work just after the Second World War (to reduce copper usage) that created the ‘ring’ circuit and our domestic fused plugs.

The temporary supply, generator or socket on the end of a building, hasn’t got these advantages, their use is restricted.  It is therefore vital to know how much power will be used.

Sorry that the preamble was so long but now we get to the important bit.  A standard domestic 13A (square pin) plug will be able to connect appliances up to about 3000 watts but will very often be used for items that use a lot less.  A kettle normally uses 1800 to 2200 watts whilst a mobile phone charger uses about 2 watts so we don’t worry about chargers unless there are a thousand of them.  To calculate the size of the supply you need to add up all of the large items, heaters, cooking appliances etc always using the power, ‘watts’ rating (many appliances are marked in amps and they will need to be converted to watts – see table 2 below).  Anything that heats things tend to be large whilst fridges, freezers and domestic electronics tend to be quite small, table 1 lists power ratings for some common items.

 

Table 1 – If you cannot find the wattage marked on the appliance use the high end of these numbers.

Kettle

1800 – 2200W

Tea urn

Assume 3000W

Fan oven

3000W

Soup urn

1000 – 2000W

Fridge

25 – 150W

Freezer

100 – 200W

Fridge trailer

Assume 3000W

Laptop, phone charger, card reader

2 – 100W

Television (32”)

150W

Small function band

2000 – 3000W

 

Table 2 – To calculate watts from amps multiply the number of amps by the voltage (230V) or use the table below.

1A

230W

2A

460W

4A

920W

10A

2300W

13A

2990W

Add up all of the wattages to get the total power required, this is the number to give to us, we can then do a calculation to work out how big a generator is required.  List the items since some are more complicated than others for instance the kettle will only be on for a few minutes and the band would generally use the maximum power for a few seconds at a time.

We will also want to know how many sockets are needed and where.  A good idea is to make a sketch of the layout, this helps with working out distances and locations.  If you can tell us what kind of socket is needed at each location, indoor or outdoor, 13 amp domestic or CEE-form/commando/caravan type it makes our specification more accurate and could save you money.

We always do our best to help you work out what is needed but the more information you can give us the better!