Considering the Pros and Cons of Going Electric (An overview of the benefits and drawbacks of owning an electric tub grinder or horizontal grinder)

Little doubt the key advantage of diesel power over electric for your tub grinder or horizontal grinder is mobility. But if your grinder can operate in a fixed location, and you have a facility with or capable of upgrading to 460V 60 Hz 3 phase,

the long term savings with an electric powered tub grinder or horizontal grinder can be substantial.  Below is a list of potential cost savings of running an electric grinder:

• No clutch; eliminates the need to monitor, adjust, and eventually replace expensive clutch components.


• No need to perform daily inspections of engine oil or coolant levels.


• No radiator; eliminates possible coolant leaks at hoses and clamps that may result in overheating.


• No fuel or oil filters to monitor and change.


• No air filters to check/clean daily and replace, or leaking connectors and intake hoses.


• No need for diesel engine overhauls usually around 6000hrs in many machines. Electric Motors are overall more reliable and durable than diesel motors. 

Now to putting some real dollar amounts for service and maintenance as supplied by a major grinder manufacture (Based on 2009 figures and a 700hp grinder over 6000 hour time frame) the diesel will be about $5.50/ton and the electric $0.50/ton.  This results in fuel consumption of approximately $60.53/hour. with off-road diesel at $2.25/gallon and electricity consummation of $31.41/hour at rate of $0.08 per kW-hr.  Using these fuel and electric rate assumption the difference in operating cost for the diesel is $34.12/hour.  6000 hrs times $34.12/hour = $204,720.  And electricity rates can often be reduced further if you grind not during peak demand periods or if interruptible power can be purchased. Using today’s diesel prices the savings is even greater since kW-hr. hasn’t changed significantly. 

Some additional considerations include;:

• Electric grinders have a separate motor driving the hydraulics.  On a diesel machine the hydraulics are driven directly from the diesel engine.  75hp is about the hydraulic load on a 1200hp diesel engine, therefore putting out 1125hp to the rotor. An electric is putting out 1200hp to the rotor.  Note, that this is really a benefit of having separate motors to run the mill and hydraulics.  While not common, some diesel machines are equipped this way as well and a similar rule of “dedicated” horsepower would apply.
• Torque is another difference between the two drive options.  The electric motors can produce up to twice the available torque that the diesel engine is capable of.
• Reduced fire risk due to elimination of diesel fuel (and possibly hydraulic systems).  Also, electric motors do not produce as much heat as diesel engines further reducing fire hazards.
• Electric grinders are much quieter and do not produce any emissions.  Both of these factors can be very important in some applications such as when operating in small pallet yards, or in California where carbon emission standards are very strict on diesel engines.

Now, why doesn’t everyone run an electric grinder?  Well, there are significant costs in running electric that have to be considered as well.  Some of the larger costs of operating an electric tub grinder or horizontal grinder you should consider are listed below:

• If you do not already have an operating location equipped with the necessary power capabilities, the set up costs can be significant; especially if the lines have to be run from very far away.
• Although there are significant fuel savings on your grinder, your support or loading equipment will use significantly more fuel if they must move material to the grinder rather than taking the grinder to the material.  This may offset some of the fuel savings realized on your grinder.
• Production rates may suffer if material has to be brought from very far away.  Similarly, operator costs will increase due to increased time loading the grinder.
• Resale value of your equipment will be greatly reduced in many cases.  Most electric grinders are not portable and so reselling and transporting the machine can lead to a reduction in resale value.  Also, there are typically far fewer applications for electric grinders, so the demand in the secondary market is much lower, further reducing the re-sale value.
• There may be some cost in lost opportunity to grind off-site on a contract basis with your grinder.  This is often difficult to quantify for first time grinder buyers that are not fully aware of what opportunities may arise once they begin grinding operations.

Please note that this discussion is only intended as an introduction of some of the factors you should consider before choosing to purchase an electric or diesel grinder.  For a more thorough analysis and discussion of your specific circumstances and application please feel free to give us a call.