The cheapest way to keep your house powered during load-shedding

South Africans should be prepared for load-shedding to be implemented on a regular basis in 2021.

Power utility Eskom is undertaking an aggressive maintenance plan which will see it take generation units offline in the next few months.

In conjunction with this, the risk of unplanned outages which may occur due to the age of Eskom’s fleet of power plants remains high.

Eskom’s latest system status report has shown that there is a high likelihood of load-shedding for the next three months with severe electricity shortages expected.

The utility’s history of load-shedding has already pushed certain households to move away completely from the electricity supplied through the national grid and install self-sufficient solar and battery systems.

However, this is not an option for the average middle-class home, with typical total costs for such a system amounting to anywhere between R100,000 and R200,000, depending on capacity needs.

Fuel-powered generators are one of the cheapest short-term choices for keeping your electricity on while load-shedding occurs.

While a moderately-sized 6.4kW petrol generator can be purchased for R10,999, a battery and inverter system with 6kW output and only 4.8kWh capacity will likely set you back over R50,000.

In addition, rechargeable lithium-ion and deep-cycle lead-acid batteries have to be replaced at a large cost every few years.

Benefits and caveats

According to energy expert Chris Yelland, diesel generators cost around R4-R5 per kWh to run.

Bear in mind that while this is much more than the price of electricity from the grid, it should be noted that the generator will only be used for the few hours of load-shedding.

Running costs for petrol generators will be slightly more as the former runs more efficiently.

The primary downside to a generator is the loud noise it makes, particularly non-inverter petrol models, which can be a nuisance to yourself and neighbours.

In addition, generators have to be serviced and maintained in order to perform reliably and should ideally not be run at full load for too long.

Comparing prices

The table below shows a comparison of the prices of various petrol and diesel generators that can provide backup power during load-shedding.

We have also included more expensive inverter generators, which operate at lower noise and more efficiently than standard petrol generators.

For the sake of affordability, we have only included products priced below R25,000.

Product Rated Power Price
Ryobi 2.7kVA Petrol Generator 2.5kW R4,999
Turner & Morris 2.8kVA Petrol Generator 2.2kW R6,199
Ryobi 3.5kVA Petrol Generator 3kW R6,665
Ryobi RG-2100I Inverter Generator 2kW R9,500
Mac Afric 8.75kVA Petrol Generator 7kW R10,995
Turner & Morris 8kVA Petrol Generator 6.4kW R10,999
Grip 7.5kVA Petrol Generator 6kW R10,999
Ryobi 7.5kVA 4-stroke Petrol Generator 6.8kW R12,499
Ryobi RG-3200I Inverter Generator 3.2kW R14,998
Mac Afric 6.5kVA Silent Diesel Generator 5kW R17,495
Etonesonic 5kVA Silent Diesel Generator 4.5kW R19,900
Turner & Morris 8kVA Silent Diesel Generator 6.4kW R24,999

Determine your demand

It is essential that the generator you wish to buy can support all the appliances you want to power.

To calculate how much power you need, will have to combine the rated output of all the appliances you would need to use at the same time.

According to Energy Use Calculator, these are the estimated average power consumption values for several common household appliances:

  • Desktop computer – 100W
  • LCD/LED Display – 30W
  • Laptop computer – 60W
  • Gaming console – 90W
  • Wi-Fi router – 6W
  • Home printer – 40W
  • LED lights – 10W
  • Incandescent lights – 60W
  • Refrigerator – 180W
  • Fridge/freezer – 30W
  • Washing machine – 500W
  • Tumble-dryer – 3,000W
  • Microwave oven – 1,500W
  • Electric oven – 2,500W
  • Stovetop plate – 1,500W
  • Dishwasher – 1,800W
  • Air conditioner – 3,500W
  • Hair dryer – 1,500W
  • Geyser – 4,000W

To use all of the appliances above at the same time, without accounting for lights, would require an output of more than 20kW – which would require a very expensive generator.

This does not take into account certain motor-driven products like a refrigerator or electric saw which will also have a higher starting wattage – which is the power required for two or three seconds – before settling down to their running wattage.

Fortunately, the odds of having to use high-consumption appliances like the microwave, stove, oven, air conditioner, washing machine, and tumble dryer together are small.

Nevertheless, it is advisable to manage your usage well, perhaps rather opting for a gas-powered stove and geyser, and using LED lights instead of incandescents.

Calculating running cost

Calculating the total cost of using a generator will depend on several factors, including:

  • How often you are subjected to load-shedding
  • How much electricity you consume while using the generator.
  • The price of petrol/diesel at a given time.

The total cost of fuel would be calculated as follows:

  • Total hours of load-shedding x Usage per hour x Cost per kWh

According to Eskom, the average daily consumption for a typical household is 30kWh. This would amount to around 1.25kWh per hour.

Under Stage 2 load-shedding, users are subjected to two hours of load-shedding six times over a 4-day period – or 12 hours in total.

If Eskom were to implement Stage 2 for a third of the days in the year, just over 120 days, the average user would therefore suffer 365 hours of load-shedding.

On the assumption of 365 hours of load-shedding, with a household that consumes 1.25kWh electricity, and a diesel generator that costs R5 per kWh to run, the total would therefore be R2,281.25.

For petrol, Assurance Power Systems claims a 5kW generator will consume around 0.75 gallons – or 2.83 litres per hour.

Assuming once again that the household uses 1.25kWh electricity, and taking the current price of Unleaded 93 petrol at R14.69 per litre, you can expect to spend around R4,740.44 over 365 hours of load-shedding.

These figures will vary greatly depending on the exact type of generator you use and any fuel-saving technologies it may employ.

The table below shows how much you can expect to pay for fuel consumption on a diesel and petrol generator over a year of Stage 2 load-shedding with varying intensities.

Stage 2 load-shedding intensity Petrol (Around R10.39 per kWh) Diesel generator (R5 per kWh)
60 days / 180 hours / 90 slots R2,337.75 R1,125
120 days / 360 hours / 180 slots R4,675.50 R2,250
180 days / 540 hours / 270 slots R7,013.25 R3,375

Now read: Eskom’s path to destruction

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The cheapest way to keep your house powered during load-shedding