Page 228

228          The WISCONSIN ENGINEER
switch-board; the public, however, except a few large consum-
ers, pays from 3 to 10 times that amount for what it uses. Steam
heating can never carry such an excess as that, but there must
be a margin for operation, distribution, overhead costs, and
profit. An attempt will be inade in the following analysis to
determine what margin exists between the cost of central sta-
tion service and private heating to cover those items.
  It has been shown above that the average fuel cost of supply-
ing radiation under the conditions named, will be about 10 cents
to 15 cents per square foot for a season of 8 months, with coal
at d$1.00 per ton. The cost can be readily computed with coal
at any other price. From a series of tests at the engineering
experiment station of the University of Illinois, (Bulletin No. 31,
Fuel Tests with House Heating Boilers, Snodgrass), the plant
efficiencies for such equipment, using the fuels named, were as
follows:
                                                      Average
     Fuel Used                                      Efficiency
                                                     (per cent)
   Illinois Coal....................                   48.86
   Po'cahontas Coal....................                50.20
   Anthracite Coal.....         ................       54.00
   Gas house coke .....          ...............       59.63
   Solvay ....................                         61.73
   The efficiencies given above for Illinois coal are no doubt some-
what higher than will be maintained in practice by the average
householder for an entire season. Based on the relative average
heating values of the fuels named and with the efficiencies above
given, the prices per ton, at which the cost of heat to the con-
sumnier would be equalized, are as follows:
                           B. t. u.   Heat              Prices
                           Per Lb.  absorbed Cost per   at which
Fuel Used                  as fired Total value Million values
                           average. Per cent Eff. B. t. u.  equalize.
Illinois  Coal  ......... .....  12,000  5,863  8.53c   $1.00
Pocahontas Coal........... 14,750     7,400     6.75c     1.26
Anthracite Coal ........... 12,700   6,858    7.28c.    1.17
Coke .....................  12,000   7,150    7.00c-    1.22
  From the above it appears that, with Illinois coal at $1.00 per
ton, we could afford to pay $1.26 for Pocahontas, $1.17 for an-