After Murdock made his first installation of gas-lighting in an industrial plant early in the nineteenth century, he published a comparison of the expense of operation with that of candle-lighting.  He arrived at the costs of light equivalent to 1000 candle-hours as follows: 

1000 candle-hours
Gas-lighting at a rate of two hours per day     $1.95
"        " "  "   "  three "    "   "       1.40
Candle-lighting                                  6.50

It is seen that the longer hours of burning reduce the cost of gas-lighting by reducing the percentage of overhead charges.  There are no such factors in lighting by candles because the whole “installation” is consumed.  This is an early example of which an authentic record is available.  At the present time a certain amount of light obtained for $1.00 with efficient tungsten filament lamps, costs $2.00 if obtained from kerosene flames and about $50.00 if obtained by burning candles.

In order to obtain the cost of an equivalent amount of light throughout the past century a great many factors must be considered.  Obviously, the results obtained by various persons will differ owing to the unavoidable factor of judgment; however, the following list of approximate values will at least indicate the trend of the price of light throughout the century or more of rapid developments in light-production.  A fair average of the retail values of fuels and of electrical energy and an average luminous efficiency of the light-sources involved have been used in making the computations.  The figures apply particularly to this country.

TABLE SHOWING THE APPROXIMATE TOTAL COST OF 1000 CANDLE-HOURS FOR VARIOUS PERIODS

Per 1000
candle-hours
1800 to 1850, sperm-oil                     $2.40
tallow candle                  5.00
1850 to 1865, kerosene                       1.65
tallow candle                  6.85
1865 to 1875, kerosene                        .75
tallow candle                  6.25
gas, open-flame                 .90
1875 to 1885, kerosene                        .25
gas, open-flame                 .60
1885 to 1895, kerosene                        .15
gas, open-flame                 .40
1895 to 1915, gas mantle                      .07
carbon filament                 .38
metallized filament             .28
tungsten filament (vacuum)      .12
tungsten filament (gas-filled)  .07

In these days the cost of living has claimed considerable attention and it is interesting to compare that of lighting.  In the following table the price of food and of electric lighting are compared for twenty years preceding the recent war.  The great disturbance due to the war is thereby eliminated from consideration, but it should be noted that since 1914 the price of food has greatly increased but that of electric lighting has not changed materially.  The cost of each commodity is taken as one hundred units for the year 1894 but, of course, the actual cost of living for the householder is perhaps a hundred times greater than the cost of electric lighting.