How much does it cost to run a Generator?

Are you considering buying a generator to mitigate the troubles of load shedding but would like to know how much it might cost to run a generator? In this article, we will look at just how much it costs to run a generator during load shedding including

  • How much fuel do generators use by size?
  • What influences the cost of running a generator?
  • How to minimize the cost of operating a generator?
  • How much are you expected to pay monthly to operate your generator?

These calculations will be for fuel costs only and do not include the cost of servicing and maintenance.

How much fuel do generators use?

Selecting the right size generator is important when it comes to efficiency. We do not recommend a Generator with a bigger capacity than 50% of constant load. If your house consumes 3kVA max we do not recommend opting for a generator bigger than 6kVA. Below we will list some generator sizes with their fuel usage under different loads:

Generator Size & Fuel TypeFuel per hour 100% loadFuel per hour 75% loadFuel per hour 50% load
3kVA Petrol Generator 1.8 l/h1.35 l/h0.9 l/h
5kVA Petrol Generator 3 l/h2.25 l/h1.5 l/h
7.5kVA Petrol Generator 4.5 l/h3.38 l/h2.25 l/h
10kVA Petrol Generator 6 l/h4.5 l/h3.0 l/h
15kVA Petrol Generator9 l/h6.75 l/h4.5 l/h
7.5kVA Diesel Generator2.0 l/h1.5 l/h1 l/h
10kVA Diesel Generator 2.5 l/h1.875 l/h1.25 l/h
12kVA Diesel Generator 2.9 l/h2.18 l/h1.5 l/h
15kVA Diesel Generator3.6 l/h 2.7 l/h1.8 l/h

These numbers a just general estimates and will vary from brand to brand but one fact that is obvious is that diesel generators consume about half the fuel of petrol generators. 

What influences the cost of running a Generator?

There are several factors that influence the cost of running a generator. Let’s have a quick look at some of the factors that influence the cost of running a generator:

  • Cost of Service and Maintenance –  You will have to maintain your generator and the Price of Maintenance and Servicing will vary depending on the Generator size, fuel type, model and brand.
  • Fuel consumption – Each generator will use a different amount of fuel depending on the size of the generator, fuel type and efficiency optimization. Diesel Generators are generally a lot more efficient than petrol generators 
  • Hours running –  A generator will consume a certain amount of fuel to power a certain amount of load over a certain period of time. Running a generator double the time at the same load will have the generator consuming double the amount of fuel.
  • Generator load or power consumed – In general generators are the most efficient between 50% and a 100% load. When generators run a lower load than 50% they will become more inefficient.
  • Repairs – When servicing and maintaining a generator properly your generator will not need many repairs. For more info on the cost of repairs please visit our Cost of Generator Repairs page.

How to minimize Generator running costs

There are many ways to minimize the cost of running a backup generator during load shedding:

  • Only run necessities when running on generator power – If you run your generator at 100% load it will consume approximately double than when running at 50% load. This means that running only essential appliances and lights when the generator is running can help you save a lot of money.
  • Choose a diesel generator – Yes the initial cost of a diesel generator is double or triple that of the same size petrol generator but with a diesel generator using half the fuel you will quickly recover the difference in price and start saving money when the generator is used frequently.
  • Service and Maintain your generator correctly – Like all combustion engines they are a lot more efficient when serviced correctly and in a timely manner.
  • Choose the right size generator – When selecting a generator try to get the right size generator so that the generator does not drop below 50% load frequently as this will affect the consumption of the generator. Generators are most efficient between 50% and 100% load.
  • Choose a high-quality generator – When buying a generator it is most often valuable to spend a bit more money and purchase a high-quality generator as they will be more efficient than most alternative brand generators. 

We recommend employing these tactics when purchasing and running a generator for maximum efficiency.

How much are you expected to pay monthly to operate your generator?

With load shedding ever on the increase, it can be valuable to know how much your monthly cost of running a generator of various sizes at different load-shedding stages might be. We opted to calculate all generators running at 75% load.

Generator l/h 75%Fuel PriceMonthly Hours Stage 2Monthly CostMonthly Hours Stage 4Monthly Cost
5kVA Petrol Generator 2.25 l/hR23.560R3175.00120R6345.00
10kVA Petrol Generator 4.5 l/hR23.560R6345.00120R12690
15kVA Petrol Generator6.7 l/hR23.560R9445.00120R18890.00
7.5kVA Diesel Generator1.5 l/hR26.560R2385.00120R4730.00
10kVA Diesel Generator 1.9 l/hR26.560R3020.00120R6040.00
15kVA Diesel Generator2.7 l/hR26.560R4293.00120R8586.00

These are just average figures and may be less or more depending on the generator type and brand and if the generator is run any time the power goes out.

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