Electric motor costs account for a large part of a farm’s monthly energy bill. If motors are not properly matched to the intended load, energy and money is wasted. Motor efficiency deteriorates over time, which also adds to energy and profit losses. Whether equipment is well worn, purchased used, or new, learning how to assess equipment efficiency and energy use is worthwhile. Assessment is best done on an annual basis to make sure your operation’s costs remain as low as possible.
Assessing and Comparing Equipment
Assessment of equipment keeps you apprised of any deterioration in efficiency and allows for comparison between existing and replacement equipment and parts. Consider these factors when shopping for the best value in new equipment or replacement parts for used equipment:
- Simplicity, reliability, availability
- Ease of maintenance
- Expected life of the equipment
- Demands it will make on existing power supplies
- Expense – both initial and operating costs. Comparison of operating costs needs to take into account operating hours, efficiency rating, energy rates, and load.
Finally, determining the payback period for purchasing energy-efficient equipment helps evaluate whether or not the purchase makes sense for your operation.
Simple payback (in years) is calculated:
Replacement Motor Cost + Installation – Utility Rebate
Total Annual Savings
To make equipment comparisons, first gather information from the equipment nameplate and manual if available. Sometimes calling the manufacturer or using on-line resources is necessary. If the equipment is old or was purchased used, the nameplate maybe unreadable, no longer accurate, or not available. If that is the case, values such as efficiency or energy use will need to be measured.
Terminology – If needed, take a moment to refresh your understanding of the following terms used in assessing equipment: load and proper loading of equipment; efficiency; energy use; electrical demand rate. [Read more]
When inspecting a nameplate, look for data that can be used to determine or calculate:
- Efficiency: HP, kWatts, Nominal (average) efficiency
- Energy Use: kWatts, Power Factor, Volts, Amps, Phase
- Power Factor: Watts, Volts, Amps, PF
Nameplate Information – If needed, take a moment to refresh your knowledge about details found on nameplates for motors, pumps, fans, heating equipment, and lighting fixtures. Review common nameplate abbreviations, units used, and certification marks. [Read more]
Calculate Efficiency and Energy Use
With the information gathered, complete the Worksheet: Calculating Farm Equipment Electric Motor Efficiency to summarize your electric motor information and calculate its efficiency and energy use.
Assessing your farm equipment sheds light on whether your motors are properly matched for the intended load. Since motor efficiency deteriorates over time, working through these calculations gives you a heads up on whether replacement with an energy efficient model can be economically justified. Understanding the terms, gathering information, and performing the calculations to assess your farm electrical equipment is a lot of work – but taking the time to do it can lead to significant cost savings.
Sources and References
Energy Demand Fact Sheet, Iowa State University
Determining Electric Motor Load and Efficiency, U.S. Dept. of Energy
Grainger Catalogue No. 402, 2011-2012 pp. 3-8: Practical reference on motor selection and the Energy Independence and Security Act (EISA) of 2007. This law requiring the sale of newer, higher efficiency motors became effective Dec 19, 2010.