The load factor

Figure out just how efficiently a building is using energy through analysis of its load profile

It is almost universally accepted that in the deregulated energy marketplace knowing a facility's load factor is critical to negotiating prices and reducing costs. But where do you start? By retrieving basic data, either over the Internet if a facility is being metered, or with a modem and software to "auto-retrieve" from the desired location.

When it comes to energy analysis, one basic tool is the establishment of the load factor. This information is critical in negotiating prices and reducing costs. Historically, energy managers with multiple sites have had to go through the rigors of analyzing their utility bills. They did this monthly, seasonally and annually, and then used these results to determine good or bad performance, and to justify capital improvements for the next year. Load factor is a new way of doing this analysis that has only become possible with the advent of computer-based "smart" meters.

WHAT IS A LOAD FACTOR?

Load factor should not be confused with power factor. Power factor measures how efficiently electricity is used. Load factor is actual consumption in kilowatt-hours divided by the worst-case consumption over a stated time period. The load factor formula is:

Kwh/kW x h = Percent of Loading (%)

Where Kwh is kilowatt-hours, kW is peak demand, and hours equal the number of days in the period times 24.

Of course, load factors can be calculated without smart meters if the hours, demand (kW) and kilowatt-hours (kWh) are known. Plugging those numbers into the load factor equations provides a real load factor without having to wait for the utility bill.

Chart A is a one-day load profile for a facility. It shows the date the data was acquired, the location of the building, a full day of activities, the peak data and the total consumption. In this case the data was recorded at 15-minute intervals.

This type of information is crucial for the pro-active building manager who is looking for the smallest of details on his building's performance. For many managers, a "find" that equates to a single digit improvement can equate to a meaningful dollar at year's end. As a result, cutting edge energy managers now look at building profiles daily.

MAXIMIZING THE RESULTS

Many energy managers spend the first part of each day reviewing load profiles. After some practice, 2-3 seconds per profile may be adequate, but additional time spent is seldom wasted since almost every profile contains some meaningful data. Sometimes it may be useful in establishing benchmarks. Other times it may lead to corrective actions being taken by field personnel.

HOW CAN LOAD FACTORS BE USED?

Load factors have many uses:

Load factor analysis is the best way to determine if a company is doing the best it can with the resources it has. Load factors demonstrate when and where a company is losing control.

Load factors are one of the best ways to determine how much energy is wasted when a store is closed. If the target is a load factor of 65 percent, but the daily profile shows 70 percent, the store may have paid 5 percent more than needed to do the job for that day. The problem may be a piece of equipment running at night when the store is closed. This type of problem is easy to fix once it has been determined that there is a problem. That's where load profiles come in handy.

Load factors are the best way to determine if a store's energy management system (EMS) and associated equipment are functioning as designed. For example, if the load factor went up 10 percent over a given month and no new equipment was added or the store wasn't open for more hours, the EMS might have been sending a signal to shut down, but a relay or two might have failed.

Load factors are critical when negotiating with a utility provider that not only wants to know how much energy will be used, but also when.

TARGET LOAD FACTORS

Load factors move up and down for different reasons, but each location should have a target load factor. The target should be what is normal for that location. If a store has extended hours of operation, a closed day for inventory, a holiday, or extended use of the building for remodel, the numbers will change. The change may show up in greater costs (increased loading) or in savings (reduced loading).

A rough target load factor can be determined by calculating the hours of operation. For example, a store open for business 14 out of 24 hours a day has a rough target load factor of 58.3 percent (14/24).

Rough target load factors can also be calculated by the month. A store open 12 hours a day, 6 days a week is open 308.57 out of a possible 720 hours in a 30-day month. That equates to a rough target load factor of 42.85 percent

WHAT TO DO WITH ALL THIS DATA?

Do a spreadsheet of all locations.

Sort the data to establish a standard.

Act on the results.

Chart B shows a $318.57 "loss" in one day for all the stores combined. In other words, according to the data, the stores spent $318.57 more on power than targeted. Considering there are 365 days in a year, that number would be significant and worth acting upon.

A good energy manager might spend time analyzing both location #1236 (best performer) and location #1238 (worst performer). If the original target was right, location #1238 is using 18.8 percent more energy than needed. The fact that it is running 93.8 percent loaded would indicate something is indeed wrong.

Load factor isn't the total answer to energy analysis, but it is appropriate in today's world of computerization, deregulation, and the Internet There is nothing more rewarding than identifying a problem today having the maintenance staff fix it tomorrow, then getting back data that says you are right on target again.

Russ Brown has 20 years of experience in energy and maintenance, and is a well-known speaker in both areas.

                         CHART B-LOAD SPREADSHEET
Location      Open kW    kWh    LF    Target %Better Rate/kWh $ Saved
              Hrs                            (Worse)          (Lost)
1234          24   500   9,710  80.9% 82%    1.1%    0.075    $7.89
1235          24   455   10,000 91.6% 82%    -9.6%   0.072    $(68.94)
1236          24   475   9,525  83.6% 85%    1.4%    0.080    $11.03
1237          24   440   9,255  87.6% 85%    -2.6%   0.077    $(18.83)
1238          24   400   9,000  93.8% 75%    -18.8%  0.078    $(131.63)
1239          24   525   11,350 90.1% 75%    -15.1%  0.069    $(118.09)
One Day Total      2,795 58,840 87.7% 81%    -7.0%   0.075    $(318.57)

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COPYRIGHT 2001 Gale Group