Bill guide
How to reduce Maximum Demand: flatten the one interval that sets the month.
Your demand charge is set by a single 15- or 30-minute interval: the highest average of the month. Bring that one interval down and the whole month’s demand charge falls with it. These are the ways plants do it, in the order that usually pays back first.
1. Find the interval that set it
The bill shows the Maximum Demand, not when it happened. Find the date and time of the peak interval and what was running then. Often it is not normal production at all but a restart after a power cut, a shift change, or a test run. How MD is calculated is explained in MD penalty.
2. Stagger start-ups
A motor’s starting current lasts seconds, so on its own it barely moves a 15- or 30-minute average. What lifts Maximum Demand is many loads coming on together and staying on: furnaces heating up, compressors and chillers all loading at once, every machine starting at shift change or when supply returns after an outage. Start the large loads a few minutes apart, in a fixed order, and the same work spreads over more intervals.
3. Improve power factor
On a kVA-billed connection, Maximum Demand is measured in kVA, and kVA rises as power factor falls. The same 400 kW load is 471 kVA at 0.85 power factor and 408 kVA at 0.98, about 63 kVA less demand without changing any machine. See improve power factor.
4. Move flexible loads out of the peak
Some loads do not have to run at the same time as the rest of the plant: water pumping, chilling to storage, battery charging, batch heating, washing. Moving them to quieter hours flattens the peak, and on a TOD tariff often moves them to cheaper units as well. See TOD tariff.
5. Watch the running interval
MD can be controlled only while the interval is still running. A live view of the current interval’s average, with an alert as it approaches Contract Demand, gives the team minutes to delay a start-up or shed a non-essential load before the interval closes.
6. Cut idle load
Machines left running with nothing to make add to every interval of the day, including the peak one. Find them from the energy meter. See machine running and idle tracking.
7. Right-size Contract Demand
Once the peak is under control, check whether Contract Demand still fits. Too high costs a minimum demand charge every month; too low brings excess-demand penalties. See Contract Demand, and work out the cost of a spike with the MD penalty calculator.
Automatic demand control
Where the same loads can be held back every time, demand control can be automatic: Modbus I/O cards switch off or delay chosen non-essential loads as the running interval nears a set limit, and release them when it falls. With KONDUKTOR® EMS this is engineered for your plant as part of your project, with the loads and limits agreed with your team.
How KONDUKTOR® EMS helps
- The running Maximum Demand interval on every meter, live, against Contract Demand.
- Alerts as demand approaches the limit you set.
- Monthly Maximum Demand history with the date and time of each month’s peak, coloured against Contract Demand.
- Per-panel demand, so you see which panel built the peak.
- A savings view that sizes the gains from MD control, power factor and Contract Demand changes.
Common questions
How do I stop motors starting together after a power cut?+
Give the large loads a fixed restart order with a few minutes between them, by procedure or with timers in their starters. The aim is to stop furnaces, compressors and chillers all loading in the same 15- or 30-minute interval when supply returns.
Do soft starters and VFDs reduce Maximum Demand?+
Soft starters cut starting current, which lasts seconds and hardly affects a 15- or 30-minute average. VFDs can reduce Maximum Demand when they let pumps and fans run slower than full speed for part of the time.
Do capacitors reduce Maximum Demand?+
On a kVA-billed connection, yes. Raising power factor lowers kVA for the same kW. A 400 kW load drops from 471 kVA at 0.85 to 408 kVA at 0.98. On a kW-billed connection, capacitors do not change Maximum Demand.
Catch the peak while the interval is still running.
Book a live demo and see the running Maximum Demand against Contract Demand on meters like yours.