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Thabiso KaliEnergy engineer · CEM

For engineers and facility managers

Load factor and time-of-use profile analyser

Two sites can use the same kWh and pay very different bills. The difference is how evenly the energy is drawn (load factor) and when it is drawn (the time-of-use split).

Inputs

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

Energy this billing period
kWh
kWh
kWh
days
Demand
kVA
Rates (from the bill)

Illustrative defaults, roughly a large-customer TOU tariff in the low-demand season. Use your own.

c/kWh
c/kWh
c/kWh
R/kVA

All charges billed per kVA this period.

R
Load shifting
%

Results

Load factor 56%, peak share 17%, all-in 186.8 c/kWh. Shifting 20% of peak saves about R32k this period.

Load factor
56%
Moderate; kVA basis 53%
Peak share
17%
48,000 kWh in peak
All-in cost
187c/kWh
Energy only 170 c/kWh
Shift saving
R32k
This period; about R391k a year

NoteA moderate load factor, typical of single- or double-shift operations. Check what sets the peak: often a few start-ups or one process overlapping another.

Energy by time-of-use period

kWh this period. Peak energy costs the most per kWh.

Peak: 48,000 kWh (17%)17%Standard: 132,000 kWh (48%)48%Off-peak: 96,000 kWh (35%)35%
  • Peak48,000 kWh · 17%
  • Standard132,000 kWh · 48%
  • Off-peak96,000 kWh · 35%

Where the bill goes

Rand this period, before load shifting.

R0R50kR100kR150kR200kPeak energy: R202kPeak energyR202kStandard energy: R185kStandard energyR185kOff-peak energy: R82kOff-peak energyR82kkVA charges: R43kkVA chargesR43kFixed charges: R5kFixed chargesR5k

kVA charges are 8% of the bill: that share is what a better load factor attacks.

Shifting 20% of peak energy to off-peak

Same kWh and the same maximum demand; only the timing changes.

MeasureNowAfter shifting
Peak energy48,000 kWh38,400 kWh
Off-peak energy96,000 kWh105,600 kWh
Energy costR468,000R435,840
Total billR515,700R483,540
All-in cost186.8 c/kWh175.2 c/kWh
Average demand383 kW383 kW
Maximum demand720 kVA720 kVA

Saving: 9,600 kWh × (420 c/kWh − 85 c/kWh) = R32,160 this period.

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
R391,280/yrAssumed

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

Assumed
R

Timers, controls or a PLC change. Enter 0 if it is only a schedule change. Default R50,000.

Assumed
years

Schedule changes drift back without follow-up. Default 5 years.

Assumed
R/yr

Any extra cost of running off-peak (overtime, supervision). Default R0.

Method

Hours in the period
h = days × 24
Load factor
LF = kWh ÷ (kW_max × h), kW_max = kVA_max × pf LF_kVA = kWh ÷ (kVA_max × h)
Rough guide: below 40% is low (peaky), 40% to 70% moderate, above 70% high (steady).
Average demand
kW_avg = kWh ÷ h
Bill
Σ kWh_p × c_p ÷ 100 + kVA_max × R/kVA + fixed
All-in cost
c/kWh = bill ÷ kWh × 100
Saving from shifting
ΔR = s × kWh_peak × (c_peak − c_offpeak) ÷ 100

Assumptions

  • One billing period at a time, with a single set of rates. Seasonal rates (high- and low-demand seasons) mean the saving from shifting varies through the year; the annual figure simply scales this period.
  • Shifted energy moves from peak to off-peak in full, with no extra energy (no storage losses) and no change in maximum demand. Shifting into a period that sets a new peak would reduce the saving.
  • All kVA-based charges are combined into one rate. Some are billed on demand in specific periods only, or on annual utilised capacity.
  • Reactive energy, levies and VAT are not shown separately; include them in the rates or fixed charges if you want them in the totals.

Sources

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