AX APPRAISAL OF POWER USED ON FARMS 43 
readjusting the equipment each time it is used and to the lack of that 
degree of famiharity of the operator Avith each new implement used 
that would obtain were he to use practically the same tools each day 
of the year. 
The necessity of keeping a large primary power plant available to 
take care of the occasional peak loads that occur in most types of 
farming results in an average load factor of only about 4 per cent: 
and since fixed charges represent a considerable part of the cost of 
operating power equipment, the result is a relatively high cost per 
unit of power produced. (See page 8.) 
In considering the costs per unit of the different kinds of power 
developed as given on page 8, it should be understood that the kinds 
of worK done are not the same with each kind of power and for 
this reason the rates are not directly comparable. Operations vary 
greatly in regard to tJae efficiency with which power may be applied, 
and if exactly the same work were to be done by any two of the dif- 
ferent kinds of power shown the cost per unit of each might vary 
considerably from the values given. It should also be understood 
that the unit used in showing costs is the horsepower-hour which is 
a measure of work done, and therefore that these values can not be 
directly compared with the horse-hour unit which is commonly used 
in cost-accounting studies but which expresses only time expended 
and not the actual work accomplished in each operation performed. 
The size of power unit employed affects the cost of an operation 
in several ways. The larger the power unit the quicker can a given 
amount of work be accomplished, with a proportionate saving in 
human labor, as a rule. Where the operation applies to some crop, 
it is also probable that the use of the larger unit will result in the 
work being done in more nearly the correct time and that a larger 
crop yield may be obtained by this means, although only a limited 
amount of information is so far available with regard to this. 
On the other hand, unless the power plant and machinery are 
employed at other work during the time saved, there will be a 
greater overhead cost for this equipment, with a resulting higher 
cost per unit of work accomplished for these two items; and although 
under ordinary conditions the saving in labor will more than equal 
the extra cost of the power and machinery, there is a limit beyond 
which this is not true. This is illustrated tor a specific case of 100 
acres of crops in the western Corn Belt in Figure 48. With condi- 
tions as given it will be seen that, up to a certain point, as the size 
of the power unit employed is increased there is an increase in the 
net profits from the production of crops on this farm, through 
reduced labor costs and increased yields, but that beyond this point 
the extra overhead cost of the larger equipment more than offsets 
the saving in labor costs. 
It should be noted that the results shown in Figure 48 are directly 
apphcable only to farms operated under exactly the same conditions 
as the one shown. If the soil should be of a nature to require more 
or less work in its preparation, if the proportion of crops produced 
should be different, il a different farm practice were followed in 
caring for the crops, if the total crop acreage were different, or if 
the cost of labor or power were different, the most profitable size of 
power unit also would probably be somewhat different from that 
shown. 
