1921 .] Marsden and Fenton.—Coal, Gas, and Electricity. 
269 
electricity given in Sections II to Y, we obtain the percentages 55 and 85 
respectively. We thus obtain for all-round use for heating and cooking :— 
Price per Unit. 
Average 
Efficiency 
Useful B.Th.U. 
for Id. 
Coal 
4s. per hundredweigh t 
Per Cent. 
25 
8,000 
Gas 
8s. 4d. per 1,000 feet 
55 
2,475 
Electricity 
ljd. per unit 
85 
1,850 
Thus gas is over three times and electricity over four times more expensive 
for general domestic purposes than coal. 
These figures disregard the labour involved in the use of the various 
fuels. This factor is a variable one for each familv and each set of con- 
ditions. We have seen that for baths a good gas-califont is probably the 
most economical; for oven cooking, electricity ; for general kitchen use, 
coal or gas ; for the main living-room, coal; for the other rooms of the 
house, gas or electricity. With regard to power and light, there can be 
no doubt of the greater economy of electricity. 
We have so far dealt with the subject from the consumer’s point of 
view only, but it is equally necessary to consider the question from the 
national point of view. The coal situation is very unsatisfactory. Accord¬ 
ing to the Director of Geological Survey, at the present and projected rate 
of consumption the total mineable coal in New Zealand is only sufficient 
for less than a hundred years. We shall, therefore, become more and more 
dependent on our imports for coal unless an efficient and sufficient substitute 
can be found. The national necessity for conservation of coal is thus evident. 
From this point of view we may compare the useful heat derived directly 
from coal or indirectly from gas and coke for domestic purposes, using the 
efficiencies of the various products given in the previous sections. 
Thermal Efficiencies of Carburizing Gas-coal in a Year's Working (1913) : 
Average for Two Metropolitan Gas Companies A 
Efficiency 
of Use. 
Heat 
actually 
used. 
'Gas sold 
TT , , , Gas loss 
Heat content] „ n ,, 
Coke sold 
\Tar 
Heat used and lost in manufacture 
Per Cent. 
24-0 
1*5 
40-0 
5-5 
29-0 
Per Cent. 
55 
25 
Per Cent. 
13-2 
10-0 
Total .. 
100-0 
23-2 
Initial coal used at 
25 
25 
* Taken from the Report to Institute of Gas Engineers . . . cited previously. 
