Your electricity bill is split into two parts. Most South African business owners only look at one of them.
The kilowatt-hour (kWh) charge — the energy you actually consumed — gets all the attention. It's the number that goes up when machines run longer and comes down when you switch off lights. It makes intuitive sense.
The other charge is less intuitive. It's called the demand charge — sometimes listed as Maximum Demand, kVA Demand, or Network Demand on your invoice. It can account for 20% to 40% of your total electricity bill, and it's entirely disconnected from how much energy you used that month.
What Is a Demand Charge?
A demand charge is based on your peak power draw during a billing period — specifically, the highest 30-minute average demand recorded in kilowatts (kW) or kilovolt-amperes (kVA) that month.
Think of it this way: your municipality isn't just supplying you with energy. It's also maintaining the infrastructure capacity to deliver that energy at your peak rate — whether you use it or not. The demand charge is how you pay for that reserved capacity.
The critical thing to understand is this: your demand charge is set by a single 30-minute window. If every machine on your site fires up simultaneously at 8am on one Monday morning, that single half-hour could set your demand charge for the entire month — even if the rest of the month is perfectly managed.
Why Demand Charges Matter More Than Most Businesses Realise
Consider a manufacturing facility paying R80,000 per month in electricity. If 30% of that bill is demand-related — a conservative estimate for most commercial and industrial accounts — that's R24,000 every month that has nothing to do with consumption.
Now consider that demand charges compound. If your facility consistently peaks above its contracted demand level, your municipality may reclassify your account into a higher tariff category. That reclassification doesn't just change one month's bill. It changes every future bill until you actively dispute and correct it.
Three Demand-Related Errors That Appear Regularly on SA Business Accounts
1. Incorrect Maximum Demand Registration
Metering equipment records your peak demand. When that equipment is miscalibrated, has incorrect CT (current transformer) ratios, or carries forward erroneous readings, the demand figure on your invoice is wrong. The bill looks reasonable. The underlying number is not.
2. Demand Contracted at the Wrong Level
Your account has a contracted maximum demand level. If this was set years ago based on different operations, or was incorrectly set at account opening, you may be paying for capacity you're not using — or being penalised for exceeding a figure that should have been updated.
3. Tariff Category Mismatch
Different tariff categories apply demand charges very differently. A business on a Standard tariff pays a flat demand component. A business on a Time-of-Use tariff pays different demand rates depending on the time of day and season. Being on the wrong category for your usage pattern could be costing you thousands monthly.
How to Spot a Demand Charge Problem on Your Bill
Pull your last three months of electricity invoices. Look for a line item labelled Maximum Demand, Demand Charge, kVA Charge, Network Demand, or similar. Note the following:
- Is the kVA figure consistent from month to month, or does it spike unexpectedly?
- Does the demand figure match what you'd expect given your operational footprint?
- Is the tariff category on your invoice actually appropriate for your business type and usage volume?
If you can't confidently answer these questions, you're not alone. Most finance managers and operations leads responsible for signing off electricity invoices have never been trained to read them. The invoices are designed to be paid, not interrogated.
What This Means for Your Business
South African municipalities have complex billing systems, annual tariff revisions (applied every 1 July), and meter reading schedules that introduce errors at multiple points. The demand component of your bill is particularly exposed to these errors because it depends on accurate metering, correct tariff classification, and appropriate contracted demand levels — all of which can drift over time without triggering any obvious alert.
The businesses most likely to have demand-related billing errors are those that have never had their accounts independently verified. Not because they're being targeted — but because errors accumulate quietly and are only discovered when someone looks.
Find Out If Your Demand Charges Are Correct
OptiRate's Rate Calculator lets you benchmark your electricity costs against verified tariff data for your municipality and business category. It takes less than two minutes and gives you a clear indication of whether your current billing is in the expected range.