What is energy demand? Part II


In my last post, I discussed the difference between kWh (total consumption) and kW (demand). In this post, I will cover some common-sense measures you can take to keep your demand charges as low as possible.

Hopefully, we now understand a little better why high demand has such an impact on power company costs and why they want and why it’s fair for them to charge a separate fee for it.

Plumbing Revisited…

You’ll recall that in the last post, I used a plumbing analogy. One customer wanted a higher volume of water flow and needed to build capacity into the system for that volume of flow. It might be fair to ask why they needed so much capacity.

A perfectly valid reason might be that they are running a manufacturing process that requires a lot of water. This is a constant requirement. Reducing flow would likely also reduce production unless they can first upgrade to newer manufacturing equipment that runs more efficiently. At any given point in time, neither option is likely available to them.

Staggering Implications!

But what if they simply have three occupants in a house who all want to take a bath at the same time each evening in three separate tubs? In order to fill all three tubs at the same time and without delay, they need a high capacity system, but otherwise they have no need for such capacity. To most of us, this example would seem silly. Rather than pay for a high capacity system, it would be much cheaper to simply stagger their bath times. Right?

But as silly as that example seems, we see its equivalent all the time. Perhaps a pump house has two large pumps. Startup demand is high for each pump but run-time demand is much lower. Starting them both at the same time can double the peak demand. On the other hand, staggering their starts by even 30 seconds can keep the peaks down nearly to individual levels. Unless there’s a very good reason for starting them at the same instant, why not stagger? It could save gallons of money.

Control Your Startup Procedures.

What do your startup procedures look like? When a shift begins, does someone simply hit the switches and go? Or is there an orderly startup procedure that minimizes simultaneous motor and ballast starts? Programmable logic controllers can automate these processes and eliminate the human error factor. Remember that the demand charge is based on the one highest peak during the month so if someone forgets to follow manual procedures – even once during the month – your demand charges are fixed by that one event. Automation solves that problem.

Other Potential Savers:

  1. Putting soft starts or VFDs on larger motors. These can help reduce peak demand amplitude.
  2. If you have supplemental power, such as cogeneration or maybe solar, try to time all of your high demand events so that they occur while supplemental power is producing. This can take some of the base out from under the demand peaks and reduce peak amplitude. Remember, however, that solar power can do nothing to reduce night-time demand peaks unless you have battery systems that spread the solar production throughout the day and night. Once again, without storage it only takes one cloudy day to frustrate your efforts, which makes PV solar an unreliable method for reducing demand.
  3. As equipment wears out, replace it with equipment that utilizes energy more efficiently.
  4. Make sure your power factor is good. Low power factor can increase the amplitude of demand peaks. Be cautious, however, when shopping for power factor correction devices. Traditional capacitor solutions can magnify harmonic distortions and increase the likelihood of harmonic resonances which can damage your equipment and shorten the life of the capacitors.

Meter, Meter, Meter!

Finally, and perhaps most importantly, it is virtually impossible to correct for the problems you don’t know about. If you really want to solve your demand and other energy problems, we recommend real-time power metering and analytics. By knowing exactly what is going on with your power consumption and demand, you can implement customized mitigation strategies to reduce your bills and increase profitability. Please Click Here to learn how Summa can help you with your energy metering challenges.


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