Maximum demand indicator (MDI)
Definition. A maximum demand indicator records the highest average power drawn over any single interval — normally thirty minutes — during the billing month, and that peak is billed separately from energy on demand-based tariffs.
Also called: MDI · Maximum demand · Recorded demand
Where you see it: On commercial and industrial bills as an MDI figure in kW or kVA, with its own charge line.
It is an average, not an instant
MDI does not catch a momentary inrush when a motor starts. It records the highest average over a fixed interval, so a two-second surge barely registers while a sustained half hour of everything running at once sets the figure for the month.
That distinction is what makes MDI manageable: you are not fighting physics, you are fighting scheduling.
One bad half hour prices the month
The demand charge is levied on the single highest interval recorded, regardless of how atypical it was. A workshop that ran every machine simultaneously once, on one morning, pays for that morning across the whole month.
Staggering start-up so that large motors do not come on together is often worth more than any efficiency measure on the same equipment.
Bringing it down
Stagger heavy motor starts by a few minutes. Interlock the largest loads so two cannot run together. Correct the power factor, because on kVA-based demand charges poor power factor inflates the recorded demand without any extra useful work.
Where a genuine reduction has been achieved and sustained, applying to reduce sanctioned load converts it into a lower fixed charge too.
Frequently asked questions
Is MDI reset every month?
Yes, the register is reset at each billing cycle so the figure reflects that month only. Some meters retain a rolling history that the DISCO can download during a dispute.
Does MDI apply to domestic connections?
Ordinary single-phase domestic tariffs are energy-only and carry no demand charge. Large three-phase domestic connections in some categories do record demand.
Related terms
- Sanctioned load — The difference between connected and sanctioned load, what happens when you exceed the sanctioned figure, and how to apply to change it in either direction.
- Power factor — What causes poor power factor in a Pakistani industrial connection, how the penalty is calculated, and whether a capacitor bank pays for itself.
- kVA versus kW — Why generators and UPS units are rated in kVA but appliances in watts, and how to size equipment correctly for a Pakistani installation.
- Fixed charges — Why some Pakistani bills carry a charge before a single unit is used, which categories pay it per kilowatt, and how it interacts with sanctioned load.
- Load factor — How to calculate load factor from your own bill, what a good figure looks like, and why improving it lowers demand-based charges without reducing consumption.
Go further
Back to the full 44-term glossary, or open your own bill with the reference number lookup.