Posted by Henri Pereira on 29th Apr 2015

For Load shedding, bigger is not necessarily better.

Most of the time, the home or business owner is always looking for the biggest possible generator for their homes or business to take them through load shedding.

One of the arguments is that they need to run their fridge, freezer and hot water geyser. But do they really?

Most loadshedding sessions imposed by Eskom are between 2 and 4 hours long, and yes in some areas 6 hours is the norm...Of course, this could change for the worse sooner than later!

Lets assume however that the average is 4 hours.

You certainly don't need to have your fridge, freezer and geyser working during that period. A fridge/Freezer will maintain for a good 12 to 24 hours without power. Likewise, a hot water geyser will supply hot water for a at least one "shared" shower during those 4 hours.

So what is really important to power up during those 4 hours of loadshedding?

For homes, it may be:

  • TV (200~300 watts)
  • Satellite Decoder (150~200 watts)
  • Wifi Modem (150 watts)
  • Laptop (180 watts)
  • Cell Charger (<100 watts)
  • A few lights (change all your lamps to LED and reduce power consumption by 80-90%) - 3 rooms with six 3 watt LED down-lights per room would draw around 54 watts)


The energy needs of the above mentioned equipment could easily be met with a 2.5 Kva Digital Inverter generator. This generator may even have enough spare capacity to power up your fridge, depending on the power (in watts) it draws .

Why people insist on going with a 7.5Kva or bigger generator for the above-mentioned, is still a mystery. Basically they will be paying 3 to 4 times more for fuel, and producing waste energy that can never be recovered. Think of it as tearing up a R10 or R20 note every hour.

For businesses, first add up the rated watts for all the devices that you need to operate during the load shedding period, including computers, monitors, servers, modems, printers, point of sale equipment, routers and the PBX (telephone system)... As for microwaves, fridges, kettles and coffee machine... I am sure most people can do without for 4 hours. The one power hungry device in an office is a photo copier, so connecting it to the generator, is something that has to be decided based on the type of business being run, and its dependency on the photo-copier. For travel agencies, delivery companies and document processing companies, there is no real alternative but to include the photocopier to the generator.

Once you know what the total load is in watts, add 20 % to it to get to the size of generator required.

For example, assuming the total load required is 1500 watts.

Size of generator in watts is  = Total load x 1.2

                                                = 1500 watts x 1.2

                                                = 1800 watts, or 1.8 Kw

If the rated power factor on the generator is 1, then you would need a 1.8Kva generator.