For engineers and facility managers

Notified maximum demand (NMD) optimiser

Your notified maximum demand (NMD) is the capacity you reserve on the network, and you pay for it every month whether you use it or not. Set it too high and you pay for idle capacity; too low and exceedances bring excess charges.

Inputs

Pre-filled with an illustrative case. Results update as you type. Jump to results

Monthly maximum demand (kVA)

The last 12 bills, oldest first: the kVA maximum (or chargeable) demand line.

Month 1

Month 2

Month 3

Month 4

Month 5

Month 6

Month 7

Month 8

Month 9

Month 10

Month 11

Month 12

Paste 12 values from a spreadsheet

One column or row, oldest first, separated by spaces, tabs, new lines, semicolons or commas.

Your NMD and capacity charges

Current NMD

kVA

Network capacity charges

R/kVA/month

Distribution plus transmission network capacity charges from your tariff.

Generation capacity charge

R/kVA/month

Enter 0 if your tariff has none.

Recommendation

Headroom above the peak

Round up to

kVA

Expected load growth

Change in peak demand over the next 12 months.

Exceedance rules

Charge exceedances (Eskom-style excess network capacity charge)

Deadband

Exceedances within this margin can be forgiven.

Forgiven exceedances

per 12 months

Results

Recommended NMD 970 kVA, saving about R97k a year against the current 1,200 kVA.

Recommended NMD: 970kVA; Peak 915 kVA + 5.0% headroom
Annual saving: R97k; Capacity and excess charges, 12 months
Current headroom: 24%; Current NMD 1,200 kVA
Exceedance risk: Low; About 9% a year at the recommended NMD

CheckThe current NMD is 24% above the highest month: capacity you pay for every month but do not use.

Monthly maximum demand against the NMD

kVA by month, oldest first. Hover a column for its value.

Maximum demand
Current NMD
Recommended NMD

Current against recommended

Next 12 months, using the demands above. Capacity charges are billed on the annual utilised capacity.

Measure	Current	Recommended
NMD	1,200 kVA	970 kVA
Annual utilised capacity	1,200 kVA	970 kVA
Capacity charges	R504,000	R407,400
Excess charges	R0	R0
Total	R504,000	R407,400
Months above the NMD	0	0
Chance of an exceedance in 12 months	0%	9%

Annual cost by NMD

Capacity plus excess charges for 12 months at each possible NMD. Below the peak you still pay for the peak (annual utilised capacity), plus any excess charges; above it, every extra kVA costs the full rate.

Show the numbers

NMD	Capacity	Excess	Total
730 kVA	R384,300	R175,750	R560,050
740 kVA	R384,300	R157,000	R541,300
750 kVA	R384,300	R116,375	R500,675
760 kVA	R384,300	R79,575	R463,875
770 kVA	R384,300	R73,275	R457,575
780 kVA	R384,300	R65,025	R449,325
790 kVA	R384,300	R45,075	R429,375
800 kVA	R384,300	R34,675	R418,975
810 kVA	R384,300	R22,625	R406,925
820 kVA	R384,300	R20,125	R404,425
830 kVA	R384,300	R16,675	R400,975
840 kVA	R384,300	R14,425	R398,725
850 kVA	R384,300	R12,175	R396,475
860 kVA	R384,300	R7,825	R392,125
870 kVA	R384,300	R2,250	R386,550
880 kVA	R384,300	R1,275	R385,575
890 kVA	R384,300	R525	R384,825
900 kVA	R384,300	–	R384,300
910 kVA	R384,300	–	R384,300
920 kVA	R386,400	–	R386,400
930 kVA	R390,600	–	R390,600
940 kVA	R394,800	–	R394,800
950 kVA	R399,000	–	R399,000
960 kVA	R403,200	–	R403,200
970 kVA	R407,400	–	R407,400
980 kVA	R411,600	–	R411,600
990 kVA	R415,800	–	R415,800
1,000 kVA	R420,000	–	R420,000
1,010 kVA	R424,200	–	R424,200
1,020 kVA	R428,400	–	R428,400
1,030 kVA	R432,600	–	R432,600
1,040 kVA	R436,800	–	R436,800
1,050 kVA	R441,000	–	R441,000
1,060 kVA	R445,200	–	R445,200
1,070 kVA	R449,400	–	R449,400
1,080 kVA	R453,600	–	R453,600
1,090 kVA	R457,800	–	R457,800
1,100 kVA	R462,000	–	R462,000
1,110 kVA	R466,200	–	R466,200
1,120 kVA	R470,400	–	R470,400
1,130 kVA	R474,600	–	R474,600
1,140 kVA	R478,800	–	R478,800
1,150 kVA	R483,000	–	R483,000
1,160 kVA	R487,200	–	R487,200
1,170 kVA	R491,400	–	R491,400
1,180 kVA	R495,600	–	R495,600
1,190 kVA	R499,800	–	R499,800
1,200 kVA	R504,000	–	R504,000
1,210 kVA	R508,200	–	R508,200
1,220 kVA	R512,400	–	R512,400
1,230 kVA	R516,600	–	R516,600
1,240 kVA	R520,800	–	R520,800
1,250 kVA	R525,000	–	R525,000
1,260 kVA	R529,200	–	R529,200

Add to a business case

What is this?

Save this result as one measure in a project kept in this browser, then combine it with results from other tools for payback, NPV, IRR and a cost curve.

Saving, year 1: R96,600/yrAssumed

Every input above is still the illustrative example, so the result is tagged assumed. Enter your own numbers to make it yours.

Name in the project

CapexAssumed

An NMD change needs no equipment; enter any utility fee or consultant cost. Default R0.

LifeAssumed

years

Years the lower NMD holds before load growth needs a new one. Default 5.

Running cost changeAssumed

R/yr

Usually none. Default R0.

Method

Recommended NMD: NMD* = ceil_step( max_m MD_m × (1 + growth) × (1 + headroom) )
Annual utilised capacity: AUC = max( NMD, max_m MD_m ); Eskom's definition: the higher of the NMD and the highest demand in a rolling 12 months.
Capacity charges for 12 months: C = AUC × (c_network + c_generation) × 12
Excess charge for the n-th exceedance: E_n = n × (MD − NMD) × c_network (first 2 exceedances within 5% of the NMD forgiven); Our reading of the Eskom NMD rules: the count multiplies the charge, so repeated exceedances escalate.
Annual saving: S = (C + ΣE) at current NMD − (C + ΣE) at NMD*
Exceedance risk (indicator): p_month = 1 − Φ( (NMD − μ) / σ ), p_year = 1 − (1 − p_month)^12; μ and σ are the mean and sample standard deviation of the 12 months. Low < 10% a year, moderate < 30%, high otherwise.

Assumptions

The next 12 months look like the last 12, scaled by the load growth you enter.
Both capacity charges are billed per kVA on the annual utilised capacity. Check your tariff: some municipal tariffs bill the NMD itself, or bill kVA differently.
Excess charges follow the Eskom-style rule above with the deadband and forgiven count you set; switch them off for tariffs without them.
The risk indicator treats months as independent draws from a normal distribution. Twelve points and seasonal peaks make it a rough guide, not a forecast.
Network charges usually depend on supply voltage and distance from the transmission network; use the rates for your supply point.
No connection charges or changes to other tariff components are included.

Sources

Eskom: Notified maximum demand (NMD) rulesExceedance deadband and excess network capacity charge.
Eskom: Notified maximum demand fact sheetHow the excess charge is calculated and how to avoid it.
Eskom: Schedule of standard prices, 1 April 2025Definitions of annual utilised capacity and the network capacity charge.
Eskom: Tariffs and charges booklet 2026/27Current rates, NMD rules and the generation capacity charge.
Engineering News: NERSA approves the generation capacity charge (Feb 2025)Background to the R/kVA generation capacity charge and its phase-in.

More technical tools

All technical tools

Technical
Power-factor correction sizing
Size a capacitor bank from kW and power factor, and see the kVA reduction, demand-charge saving and payback.
You need
kW at maximum demand, power factor now and target, R/kVA demand charge
You get
kvar required, bank size, kVA and current reduction, saving, payback
Open the tool
Technical
Load factor and time-of-use profile analyser
From kWh by time-of-use period and the maximum demand, find the load factor, peak share, all-in cost per kWh and the value of shifting load out of peak.
You need
Peak, standard and off-peak kWh, maximum demand, c/kWh rates
You get
Load factor, TOU split, c/kWh, saving from load shifting
Open the tool
Technical
Solar PV yield and self-consumption estimator
Estimate generation for a South African city from typical specific yields, then split it into self-consumed and exported energy and value both.
You need
System size (kWp), city or specific yield, self-consumption share, tariff
You get
Annual kWh, self-consumption and export, savings, payback, NPV
Open the tool

Also for finance, commercial and investment people: Business case, Solar PPA project finance and more.