740 ECONOMICAL ASPECTS 



heads above 80 feet. The value of one runner including freight 

 and erection would be about $27,000. 



About seven low-head units are required to operate at 80 foot- 

 head to produce 800,000 H.P. with a decreasing number at the 

 higher heads where the erosion would be most severe. If we 

 assume to replace all seven runners every three years, the annual 

 additional charge would be $63,000, say $75,000. This item is 

 very small compared with the additional profit which the surplus 

 power should bring. 



It might be assumed roughly that eleven months' surplus 

 power be worth 80 per cent of the value of continuous power, ten 

 months' power 60 per cent and eight months' power 30 per cent. 



If the various prices now be weighted according to the amount 

 available, and using the price of primary power as unity, there will 

 result: 



480,000X1.00=480,000 

 120,000 X .80= 96,000 

 100,000 X .60= 60,000 

 100,000 X .30= 30,000 



800,000 actual or 666,000 weighted power 



The quotient of these, totals or 0.8333, now represents the aver- 

 age unit value of all power, as a proportion of the value of primary 

 power, and 666,000 represents the equivalent primary power to 

 produce the same income. If all power were to be sold at prices 

 bearing the above ratio to each other, the actual costs of pro- 

 duction of primary power would then be obtained by first adding 

 $75,000 to the annual charges and then dividing by 666,000. 



Based upon 3 per cent interest: 



Former annual charge $3,462,900.00 



Add for runner depreciation 75,000 . 00 



Total $3,537,900.00 



Add 25 per cent 884,000.00 



Use $4,421,900.00 



Cost per peak primary horse-power $6 . 63 



Cost per 11 mo. surplus H.P 5 . 30 



Cost per 10 mo. surplus H.P 4 . 00 



Cost per 8 mo. surplus H.P 2 . 00 



