Introduction
Most equipment does not continuously operate at its rated, name plate capacity. A Load Factor is most often an estimate of some percentage, lower than 100%, to account for the equivalent Full Load Hours, or average energy usage. Some equipment may actually be “on” and may even be running continuously, but not drawing a full load.
General Procedure for Estimating a Load Factor
- Obtain the actual name plate rating of the equipment. For electric equipment, the rating may be in Horse Power, watts, or amps at a certain voltage. For gas equipment, the rating will be in BTUs.
- Through observation and/or questions, determine the “on” period of operation, in hours per day and days per week
- Determine how the equipment is controlled; ie: does it have an on/off cycle that is manual or automatic; does it have a less-than full-on ability, such as variable speed control or variable fire burner
- Count the number of motors/compressors/burners that the equipment has. For example, a chiller with two compressors and motors that both have variable speed will have a substantially different load factor than a unit with a single fixed-speed motor
General Rules of Thumb
(Name Plate Rating Input) x (On-Hours per Day) x (Load Factor) = Average Usage per Day
|
Equipment |
Load Factor |
Comments |
| Space Heating | 60% | For equipment that actually runs; 0% for standby equipment; less for shoulder months |
| Air Conditioners | 60% | For mid-summer months; less for shoulder months. |
| Air Compressors | 60 – 80% | For heavy use applications; |
| Refrigeration | 40 – 100% | Lowest during winter months; consider volume of warm product moving in for production applications; |
| Food Preparation | 30 – 80% | Use lower number for average daily, and higher number for hours limited to peak service times |
| Lighting | 100% | Occupied hours and up to 50% for unoccupied hours depending on building use and cleaning schedule |
| Office Machines | 10% | Copiers, faxes, etc. |
| Computers | 100% | Servers and main frames are always on; desk top units may always be on but go into a power saver mode when not in use |
| Gas Process | 20 – 100% | Highly variable; batch processes with long cycle times tend to have lower load factors due to hold and cool-down parts of the cycle. Continuous processes have load factors that resemble the amount of product throughput – the faster and higher volume of product, the higher the load factor. Batch process equipment tends to have larger burners for faster heat-up, therefore the average usage is lower over the full cycle. |
| Stamping and Milling Machines | 40 – 60% | Most electric motor driven equipment that cycles has less than a 50% load factor; even lower with variable speed drives |