Hanno Labuschagne29 February 2024

Subscribe

It could cost typical South African households anywhere between R361 and R5,776 per month in fuel for petrol generators powering their home appliances under continuous load-shedding.

While an inverter and battery combo provide a great way to have backup power during load-shedding, it is still substantially more expensive than a fuel-based generator — at least in terms of initial cost per kW of output capacity.

Generators are also an option for households that want to go fully off-grid but cannot afford to oversize their systems’ panels and batteries sufficiently for full protection against prolonged periods with little solar generation.

The big downside to using a generator is that it consumes fuel, which you must top up regularly if load-shedding becomes frequent.

Most generators intended for general household use run on petrol, while those in large-scale industrial applications tend to be diesel-powered.

Over the past few years, the prices of both these fuels have increased substantially.

At the time of publication, the inland prices of one litre of unleaded 95 and unleaded 93 petrol stood at R23.24 and R22.92, respectively.

These are expected to increase by more than R1 when the latest fuel price adjustments kick in on Wednesday, 6 March 2024.

Load-shedding hours vary between areas

To calculate how much a household with a generator would spend on fuel to provide backup power during various stages of load-shedding, the number of hours of load-shedding per month must first be determined.

This can vary greatly from one area to the next, even during the same stage of load-shedding.

MyBroadband previously compared the amount of load-shedding time endured in major cities and towns in South Africa in 2023 using data from EskomSePush.

We found that areas in Polokwane, Mbombela, Gqeberha, and Pietermaritzburg had significantly fewer load-shedding minutes during the year than the average.

This is because load-shedding frequency and lengths are determined by each supplier, in line with NRS048-9 guidelines.

For non-Eskom Direct customers, the power utility leaves the implementation of load-shedding up to each municipality, with guidance on how much demand they must remove from the grid during each load-shedding stage.

The amount that must be cut is measured as a proportion of a municipality’s typical demand — not a specific number of megawatts.

The table below shows how many hours without power the average household should expect due to load-shedding from stage 1 to stage 8, according to Eskom.

For context, Johannesburg residents have often complained that they experience over 11 hours of load-shedding per day on stage 6.

Load-shedding stages
Stage	Hours shed per week	Hours shed per day
1	10.5	1.5
2	21	3
3	31.5	4.5
4	42	6
5	52.5	7.5
6	63	9
7	73.5	10.5
8	84	12

Even if load-shedding were consistent across all neighbourhoods, a precise calculation of the costs would be a major undertaking.

Firstly, it will require differentiating between individual generator models, as these have varying fuel consumption rates.

In addition, conventional generators tend to become more efficient when they are closer to running at full capacity, further complicating the calculation.

Secondly, South African households have widely varying electricity consumption habits.

To estimate how much it could cost to run a petrol generator, we used the average fuel consumption of three models from Mac Afric, a popular local generator brand.

These were as follows:

• 2.8kVA petrol generator — 0.82 litres per hour at full load of 2kW
• 6.5kVA petrol generator — 2.2 litres per hour at full load of 5kW
• 8.75kVA petrol generator — 2.84 litres per hour at full load of 7kW
• Average petrol consumption — 0.42 litres per kWh

Regarding energy consumption, we assumed three usage levels — a moderately low consumption of 600kWh per month, Eskom’s average of 900kWh, and a high consumption level of 1,200kWh.

The estimated fuel consumption and costs for each stage of load-shedding for these homes’ usage are shown in the table below.

Fuel usage and costs
Level of energy consumption	Stage	Petrol consumed per day	Price of petrol per day	Price of petrol per month
Low (600kWh/month)	1	0.53	R12.03	R360.99
	2	1.05	R24.07	R721.98
	3	1.58	R36.10	R1,082.97
	4	2.10	R48.13	R1,443.96
	5	2.63	R60.17	R1,804.95
	6	3.15	R72.20	R2,165.94
	7	3.68	R84.23	R2,526.93
	8	4.20	R96.24	R2,887.92
Mid (900kWh/month)	1	0.79	R18.05	R541.485
	2	1.58	R36.10	R1,082.97
	3	2.36	R54.15	R1,624.46
	4	3.15	R72.20	R2,165.94
	5	3.94	R90.25	R2,707.43
	6	4.73	R108.30	R3,248.91
	7	5.51	R126.35	R3,790.40
	8	6.30	R144.40	R4,331.88
High (1,200kWh/month)	1	1.05	R24.07	R721.98
	2	2.10	R48.13	R1,443.96
	3	3.15	R72.20	R2,165.94
	4	4.20	R96.26	R2,887.92
	5	5.25	R120.33	R3,609.90
	6	6.30	R144.40	R4,331.88
	7	7.35	R168.46	R5,053.86
	8	8.40	R192.53	R5,775.84

—