Your July bill arrived. There’s a line on it you don’t recognise. It says reactive energy. The number next to it is not small.
You didn’t buy a machine. You didn’t add a shift. Nothing on the floor changed.
And this line wasn’t on your March bill at all.
Why is there a reactive energy charge on my Eskom bill?
There is a reason, and it’s on page two where the charge codes live. It’s also one of the cheaper things on your bill to fix.
First, let’s rule out the usual suspects.
It isn’t load shedding. That lowers your bill, it doesn’t add lines to it.
It isn’t the April increase either. That was 8.76% for Eskom-direct customers, it landed four months ago, and a percentage increase doesn’t create a new charge code.
And it isn’t your demand charge. Demand is a separate line. That one bills you for the biggest gulp of power you took in the month.
This charge isn’t about how much power you used. It’s about the quality of it.
What reactive power actually is
Pour a beer too fast and you get foam. The glass is full, but not all of it is beer. Electricity works the same way.
The beer is real power. It turns your pumps and drives your mills. It’s measured in kW, and the meter counts it in kWh.
The foam is reactive power. It does no work, but it still has to travel down the wire.
Reactive power is measured in kVAr. Over a month it adds up as kVArh — the unit on the mystery line.
So where does the foam come from? Motors. Transformers. Pumps. Compressors. Anything that builds a magnetic field to do its job.
They pull extra current to build that field. It goes out and comes back, doing nothing on the way. But Eskom’s network still had to carry it.
Power factor is simply how much of your glass is beer.
A power factor of 1.0 is a perfect pour. No foam. Sites with heavy motor load often sit well below 0.96, and most owners have never been told their number.
The rule, and the free allowance
Eskom doesn’t charge you for all your foam. It gives you an allowance first.
You get an allowance of kVArh worth 30% of your kWh. Above that, you pay per unit.
But read that carefully. It’s 30% of the kWh you use in the peak and standard periods only.
Your off-peak units don’t count. So if you run night shift, your allowance is smaller than your total consumption suggests. Don’t take 30% of the number at the bottom of your bill.
That 30% is the same thing as a power factor of 0.96. Eskom’s Schedule of Standard Prices says both in the same sentence. You don’t have to be perfect, just reasonable.
Which tariff are you on? It changes the number
This charge exists on the time-of-use tariffs. The rate is not the same on each one.
Excess reactive energy, winter rate, excluding VAT
Megaflex — 34.49 c/kVArh (39.66 including VAT)
Ruraflex — 21.57 c/kVArh (24.81 including VAT)
Miniflex — 15.02 c/kVArh (17.27 including VAT)
On all three, the summer rate is 0.00.
Megaflex is the urban industrial tariff, for sites above 1 MVA of notified maximum demand. That’s your contracted supply size, not what you actually pull.
Ruraflex is its rural twin. If you run a packhouse, a mill, a cold chain or an irrigation scheme, this is usually your tariff.
Miniflex covers 16 kVA up to 5 MVA, so it picks up the smaller end of a site portfolio.
Check your tariff name before you do any sums. The Megaflex rate is more than double the Miniflex one.
One more detail, and it matters. On Megaflex and Miniflex the sum is done every 30 minutes, not once at month end. So a good afternoon doesn’t cancel out a bad morning.
Here’s the part that catches people
The reactive energy charge only exists in winter.
Eskom calls June, July and August the high-demand season. That’s when the charge applies.
From 1 September the rate drops to zero. Not lower. Zero.
So your bill appears to fix itself. The strange line vanishes, and you stop asking about it.
Then next June it comes back, and you’ve had nine months to forget it existed.
That’s the trap. The charge isn’t hidden. It just disappears before anyone deals with it.
What it costs — a worked example
Real numbers. These are Terawatt’s modelling assumptions, not your bill.
Assume a site on Megaflex, supplied at 500 V to 66 kV, within 300 km. It records 200,000 kWh across the peak and standard periods in July, at a power factor of 0.85.
Step one. The free allowance.
30% of 200,000 kWh = 60,000 kVArh free
Step two. What 0.85 produces. At a steady 0.85, a site draws about 62 kVArh per 100 kWh. That ratio is geometry, not a tariff — the same maths that turns 0.96 into Eskom’s 30%.
200,000 kWh × 0.62 = 124,000 kVArh recorded
Step three. The excess.
124,000 − 60,000 = 64,000 kVArh over the allowance
Step four. The bill.
64,000 × 34.49c = R22,073.60 for the month, excluding VAT
Across the three winter months, that’s R22,073.60 × 3 = R66,220.80 a year.
The same excess on Ruraflex, at 21.57c:
64,000 × 21.57c = R13,804.80 for the month, excluding VAT
And on Miniflex, at 15.02c:
64,000 × 15.02c = R9,612.80 for the month, excluding VAT
Same foam. Same meter. Three different bills.
One thing for the agri readers. Ruraflex works the sum across the whole billing period, not per half hour. A short, hard season averages into the month rather than being caught interval by interval.
Now run the same site at a power factor of 0.96. It records 60,000 kVArh or fewer. That’s inside the allowance. The charge is zero.
Same machines. Same production. Same kWh. The difference is correction gear in a cabinet.
One caveat: this assumes your power factor holds steady. Real sites wobble, and Megaflex assesses each half hour on its own. Use this to decide whether to measure, not what to buy.
“There’s no reactive line on my bill” — you might still be paying
Nightsave Urban has no reactive energy charge at all. Not a cent. But that doesn’t make poor power factor free.
It bills its big demand charge in kVA, not kW. And kVA is the whole glass — beer plus foam. Poor power factor inflates the glass, so it inflates the charge.
Assume a site drawing 500 kW of real load at peak.
At 0.85 power factor: 500 ÷ 0.85 = about 588 kVA
At 0.96 power factor: 500 ÷ 0.96 = about 521 kVA
That’s 67 kVA of pure foam, billed every month.
In winter, the charges that move with demand are R332.91 plus R26.29 per kVA per month.
R332.91 + R26.29 = R359.20 per kVA
67 × R359.20 = R24,066.40 a month, excluding VAT
No reactive line on the bill. The money leaves anyway.
One caveat here too. Eskom bills this on your single highest half hour in the peak periods. So what counts is your power factor at that exact moment, not your average across the month. A site that runs poorly all day but well at 5pm pays less than this sum suggests.
Who this post is not for
If your power factor already sits at 0.96 or better, you are inside the allowance and there is nothing here to collect. Correction gear would be money spent for nothing. Check before you shop.
If your load is mostly resistive, this probably isn’t your problem either. Electric furnaces, resistance heating, drying elements and kilns pour very little foam. A site built around those can sit near 1.0 without trying.
This is a motor problem. Irrigation pumps, packhouse refrigeration, mills, conveyors, compressors, extrusion, welding bays. If that’s not your load, spend your attention elsewhere on the bill.
And if you’re on Businessrate, at 100 kVA or under, the charge doesn’t exist on your tariff at all.
What to do this week
Four steps. The first two cost nothing.
1. Find the line. Get your July bill and look at page two, for the word “reactive” or the unit kVArh. Write down the rand value.
2. Find your power factor. Many bills print it. If yours doesn’t, your metering data will. Ask your account manager or metering provider.
3. Measure before you buy. A logger on your main incomer for a week shows how power factor moves through a shift. It’s cheap, and it tells a supplier how to size the gear.
4. Size correction on the data, not the nameplate. A capacitor bank is the usual fix, and modest money next to a battery. Oversized correction causes its own problems.
One more thing. The charge stops on 31 August, and your motivation will stop with it. Do this in spring, while you still remember what July cost you.
Common questions
Will a battery fix my power factor?
Not on its own. A battery shifts energy through time — it cuts peaks and moves load to cheaper hours. Power factor is a different problem, and a battery is a very expensive capacitor. Fix it with correction gear. Our guide to peak shaving and demand charges covers what a battery does do.
Will solar fix it?
Not by itself. Solar reduces the kWh you buy in the daytime. But your allowance is 30% of those same kWh. So the allowance shrinks while your motors carry on drawing the same reactive power. That can leave the charge higher, not lower. Some inverters can be set to supply reactive power, which does help. Ask your installer whether yours can.
Does power factor correction help in summer too?
Not through this charge. On Megaflex, Miniflex and Ruraflex the rate is zero from September to May. On a kVA-billed tariff like Nightsave Urban it helps all year, but far less in summer, because the demand charge itself drops.
My power factor is 0.92. Is that a problem?
It’s below 0.96, so you’d be paying something. Whether it’s worth fixing depends on how many kWh you push through the peak and standard periods, and which tariff you’re on. Do step one first.
The short version
There’s a charge on your winter bill that isn’t on your summer bill. It isn’t demand, and it isn’t the tariff increase.
It’s foam, and you’re paying for the glass.
Start with page two of your July bill. Or send it to us and we’ll read it for you. We’ll also tell you whether this applies to your site at all.
For the rest of the bill, start with why your business electricity bill is so high. Then read how winter tariffs and demand charges work.
Rates quoted are from Eskom’s Schedule of Standard Prices, effective 1 April 2026. They are the non-local-authority rates for a transmission zone under 300 km. The supply band is 500 V and above, and below 66 kV. Reactive energy rates are taken from the Megaflex, Miniflex and Ruraflex tables. Your own tariff, voltage and zone may carry different rates. Municipal customers are on their municipality’s tariff, not an Eskom one, and should check their own schedule. Worked examples are Terawatt modelling assumptions and are labelled as such.
