Eskom Megaflex is eleven charge components. Most billing systems model three.
A South African utility tariff is not a unit rate. It is a structure of energy charges that change by time of day and season, demand charges with their own reset rules, network and capacity charges, reactive energy penalties, and levies — any of which can change mid-billing-cycle. MOL models all of it, because a bill that is 96 per cent right is a bill that gets queried.
Somebody has to read the NERSA determination.
There are roughly 350 promulgated tariffs in South Africa — Eskom, plus every Metro, City and Municipality with its own set. They change on their own timetables, in their own formats, and not always cleanly.
PMT keeps a team whose job is to track that and keep the models current. It is unglamorous, it never finishes, and it is the reason a MOL bill reconciles against the utility's own invoice rather than approximately matching it.
- Time of use
- Peak, standard and off-peak by season, weekday and public holiday.
- Maximum demand
- Sliding-window and fixed-interval demand, with the correct reset behaviour.
- Inclined block
- Stepped rates where the unit price changes with cumulative consumption.
- Seasonal
- High and low demand season rates, and the changeover mid-cycle.
- Network and levies
- Capacity, network access, ancillary service, reactive energy penalties.
- Summated accounts
- Multiple supply points billed as one, with demand diversified correctly.
Are you on the right tariff? You cannot answer that from the rate card.
Utilities offer several tariff options and the cheapest one depends on your consumption shape, not just your consumption. A tariff that is cheaper per unit can cost more once your demand peak lands in the wrong half hour.
MOL answers it properly: it runs the comparison across twelve months of your actual half-hourly data, so seasonal changes in both your usage and the tariff rates are accounted for. Any two tariffs, from any financial periods, against a load profile from any period.
One worked example
Run the same tariff across two financial periods against a customer's own load profile, and you get the increase that actually landed on that customer — about 15 per cent in one case, against a stated average increase that was substantially lower.
Averages are computed across every customer on the tariff. Yours is computed across your building. They are rarely the same number, and the difference is invisible until somebody runs it.
The cases that break billing systems
A tariff change mid-cycle
The rate changes on the first of July and your cycle runs to the fifteenth. MOL bills each half hour on the tariff that was in force when it was consumed, not a prorated approximation of both.
Demand across summated points
Three intakes, three demand peaks, at three different times. Adding them overstates the charge. MOL sums the interval data first and takes the demand from the total, which is what the utility does.
A reading that arrives late
Data recovered after the bill was raised does not silently change history. The adjustment is visible, attributable, and traceable to the interval that moved.
Preflight validation
Everything gets checked before the run, not after the query.
A billing run is the last point at which a data problem is cheap. Afterwards it is a credit note, a re-run, and a conversation.
MOL runs a preflight pass across the whole billing set first, and it spans more than the consumption figures — account, meter point, tariff assignment, meter, phasor and profile, because a wiring fault and a missing interval both end up as a wrong invoice.
Profile checks
- Missing intervals, and zero values during known operating hours
- Readings below the meter's theoretical accuracy limit, or above its theoretical maximum
- Active energy recorded with no corresponding reactive energy
- Quadrant data inconsistent with the installation
- Power factor far enough out to indicate a fault rather than a load
Phasor checks
- Voltage imbalance across the three phases
- Current imbalance beyond what the load explains
- Zero current on a phase that should be carrying
- Reverse energy on a single phase — the signature of a reversed CT
These sit in the billing gate deliberately. A reversed CT is an engineering fault, but it arrives as a revenue error, and the billing run is where it gets caught.
A landlord reselling electricity is not setting a price.
Under the Electricity Act, a reseller must charge tenants as though they were buying directly from the municipality — on the tariff promulgated for that area, without markup.
Which makes tenant billing a compliance obligation rather than a commercial decision, and makes getting the tariff model right a matter of being able to show that the charge is the promulgated one.
Want to see this on your own data?
We will run it against a month of your readings and show you what comes out.
Talk to us