706 ECONOMICAL ASPECTS 



resented either by cash or plant, must be included in the estimate. 

 The length of time for which to compute the same will naturally 

 vary with the time required for the construction, but as a rule it is 

 figured at the full annual rate for one-half the construction period. 



Working capital of a reasonable amount must, of course, be 

 provided for carrying on the business and must be considered as a 

 part of the property. 



From the above it is seen that the overhead charges form a large 

 percentage of the cost of developing a system and it may approx- 

 imately be taken as from 20 to 30 per cent of the physical cost. 



Cost data on hydro-electric plants are scarce, and when ob- 

 tained the greatest caution must be exercised in using them for 

 estimating other projects. They are greatly affected by local 

 conditions, as, for example, the nature of the soil in determining 

 the cost of excavation, the price paid for labor, freight and trans- 

 portation charges, market value of raw and other material, appa- 

 ratus, etc. 



In order, however, to give the reader an approximate idea of 

 the costs involved, the following figures are given. They are 

 based both on actual costs and on estimates under normal con- 

 ditions, but the authors wish again to repeat their caution as 

 to a careful discrimination of their use. 



ESTIMATED COST OF 600 Kw. HYDRO-ELECTRIC POWER STATION 



It is proposed to install two units, each comprising a 500-H.P. 

 turbine operating under a 60-foot head and driving a 300-Kw. 

 generator. Two separately driven exciter units and complete 

 switching equipment, but no step-up transformers. The dam is 

 already provided and is not included in the estimate. 



Penstock and flume, including headworks, connections, tunnel, etc. $22,500 



Regulating tank, including housing 1,500 



Power station; foundation and buildings complete with interior work 



and fittings 9,800 



Staff house and miscellaneous 3,000 



Equipment in power-house, consisting of two 500-H.P. turbines with 



governors, generators, exciters, switching, equipment, etc 30,200 



Total $67,000 



Add for contingencies, engineering, supervision and inspection, 12 



per cent, say $8,000 



Grand total $75,000 



