The New Law's Broader Coverage, Tighter Standards Save Energy and Money
The Energy Independence and Security Act of 2007 (P.L. 110-140, usually called "EISA") will go into effect on December 19, 2010. If you specify or purchase electric motors, the law will affect how you do your job. If you own or manage a business, it will ― or at least, it can ― improve your company's bottom line by cutting your energy costs for years to come. EISA will/can do that because it raises the mandated nominal full-load efficiencies of many types of electric motors in commercial and industrial service. More-efficient motors save money.
Just a few paragraphs in EISA's 300-plus pages deal with motors, but they're important. Why? Because motors account for nearly 50 percent of total U.S. energy use and two-thirds of all electrical energy used in industrial settings. Also, and here's the important statistic: the cost of operating an electric motor can run up to 25 times the motor's purchase cost per year.
Upping the Ante
EISA is the most recent in a series of energy-saving, motor-related laws passed over the past 20 years, each one upping the efficiency ante on the previous version.
The Energy Policy Act of 1992 (EPAct 92) was the first major energy law to require minimum, nominal, full-load motor efficiency ratings. 1 It applied specifically to "general purpose, T-frame, single speed, squirrel cage, induction type; 230/460-V, NEMA Designs A or B, continuous rated, 60 Hz, from 1 to 200 hp, 2-, 4- and 6-pole (3600-, 1800- and 1200-rpm), open and enclosed"; in short, most of the motors commonly specified for industrial equipment. The motors, which came to be known as "EPAct motors", are still commercially available. Their nominal efficiencies are between one and four percentage points higher than those of the so-called "standard-efficiency motors" that had dominated the market for decades. EPAct 92 doesn't address special-purpose motors or motors of sizes, frames, speeds or voltages other than those listed. Nominal efficiency values for each type and size of motor covered by the law are spelled out in Table 12-11 of the National Electrical Manufacturers' Association publication, NEMA MG 1-1998 R3.
Next came the Energy Policy Act of 2005 (EPAct 2005), which established the now-familiar NEMA Premium® efficiency ratings as the basis for federal motor purchases. The relevant efficiency ratings are given in a (revised) Table 12-11 in NEMA MG1-2001. 2 NEMA Premium motor efficiency ratings are up to several percentage points higher than those of their EPAct predecessors.
EPAct 2005 applies only to federal motor procurements. EPAct motors can be sold in the public domain until EISA takes effect. While EPAct 2005 deals with the same types of motors listed in EPAct 92, the law broadens the size range to include motors from 1 to 500 hp. NEMA took this change into account in the 2006 version of MG 1 Table 12-12, which was expanded to include NEMA Premium ratings for the larger motors. EPAct 92 minimum nominal efficiency ratings are retained in MG 1-2006 as Table 12-11.
Expanded Coverage, Higher Minimums
EISA does not address federal procurements. Instead, like EPAct 92, it sets standards for motors per se. The act has several important provisions:
First, it expands the types of motors to which efficiency standards apply. They include:
- "Traditional" general-purpose motors, i.e., those defined above for EPAct 92. EISA designates them as "Subtype I" motors.
- A new, "Subtype II" classification that includes certain motors previously exempted from minimum efficiency requirements. The motors incorporate design elements of Subtype I general-purpose motors but can be configured as U-frame motors; NEMA Design C motors; close-coupled pump motors; footless motors; vertical solid shaft normal thrust motors (as tested in a horizontal position); eight-pole (900 rpm) motors, and polyphase motors with a voltage of not more than 600 V (other than 230 or 460 V).
Second, EISA assigns minimum, nominal, full-load efficiency ratings according to motor subtype and size:
- Subtype I motors sized from 1 to 200 hp and manufactured (in the wording of the law) "alone or as a component of another piece of equipment", must meet the NEMA Premium minimum efficiencies listed in MG 1-2006, Table 12-12.
- Subtype II motors are required to meet the less stringent EPAct 92 minimum nominal efficiencies as published in MG 1-2006, Table 12-11.
Finally, the new law grants two exceptions: One is for Subtype 1, NEMA Design B motors sized between 200 and 500 hp, which need only meet EPAct 92 efficiency ratings, MG1-2006, Table 12-11. (Whether or not EPAct overrides this exception for government procurements is not spelled out in the Act.) The same exception is made for fire-pump motors.
Table 1 may be a useful guide to the several laws, publications and revisions surrounding motor efficiencies.
|Motor Type & Size||Applicable NEMA MG 1-2006 Table Number|
|Subtype I, 1-200 hp||12-12, (NEMA Premium)|
|Subtype 1, NEMA Design B, 200-500 hp||12-11, (EPAct 92)|
|Subtype II, 1-200 hp||12-11, (EPAct 92)|
|Fire-Pump Motors, all sizes||12-11, (EPAct 92)|
How Will EISA Affect Your Company?
EISA only affects new motor purchases made after December 19, 2010. Existing motors are now, and will be, grandfathered and can be rebuilt as usual. However, rebuilding is usually a wasteful, costly choice. At best ― and that isn't always the case ― it will restore the motor to its original efficiency.
Installing more efficient motors almost always saves enough money to pay off the new motor quickly. There are exceptions: motors that operate only intermittently (low duty cycle) will save less since they only accrue savings while running. Low utility rates (the national industrial average is around $0.07/kWh) will also stretch out the pay-back time. On the other hand, many utilities and some jurisdictions offer rebates or credits to companies that install more efficient motors, a practice that reduces up-front cost and shortens pay-back times considerably.
Look at some numbers: Table 2 lists payback periods for a few EPAct and NEMA Premium motors compared with rebuilding existing standard-efficiency motors. Analyses are based MotorMaster+ using data supplied by motor manufacturers. Motors are assumed to operate at 75% load for 8,000 h/y. The utility rate used is $0.067/kWh.
|Replace with NEMA Premium Motor vs. Rewind Standard-Efficiency Motor|
|HP||Annual Savings||Payback, years|
For all but large motors (which tend to be highly efficient), the replace vs. rewind decision is obvious. Think of a one-year payback as a 100% return on investment and upgrading to a NEMA Premium motor becomes an obvious choice.
Going One Step Farther
A growing number of commercially available, general-purpose motors now exceed NEMA Premium efficiency standards. Some of these motors are equipped with die-cast copper rotors to reduce I 2R losses. Better-than NEMA Premium motors are not specifically addressed by EISA; however, their extra-high efficiency make them wise choices for large energy/cost savings and rapid pay-back. Table 3 lists a few of these motors, chosen because they display at least 10% lower total electrical losses than an average NEMA Premium motor of the same size as defined by MotorMaster+. Readers are urged to consult the DOE software for manufacturers' names and model numbers.
|HP||Manufacturer||Full-load Efficiency, %*||Annual Savings||Payback, y|
Whether you choose a NEMA Premium motor or one that exceeds NEMA Premium standards, the data are clear:
- Old, inefficient motors waste hundreds to thousands of dollars per year.
- Higher-efficiency motors yield larger savings and faster pay-backs.
- Develop an energy program that includes motors.
- Evaluate your motor inventory using MotorMaster+, available by request at AMO Tools Help Desk.
Then go and save your company some money.
- The term "minimum, nominal, full-load efficiency" refers to ratings displayed on nameplates. It is useful for comparing motor efficiencies. However, since most motors operate more efficiently at lower loading, readers may wish to apply efficiency data reported for 50% and 70% loading as reported in the DOE's MotorMaster+ software available by request at AMO Tools Help Desk .
- Today's NEMA Premium standards are products of work jointly undertaken by the National Electrical Manufacturers Association and the Consortium for Energy Efficiency.