sumer's maximum demand to be the greatest rate of taking current during the year, it has been considered fairer to the consumer to take the mean of six winter months' readings of a maximum current indicator, which, by its very nature, takes quite ten minutes to fully register the passing current. For the purposes of calculating the cost of supplying any individual consumer, it is then assumed that the mean demand as above defined, bears to the total of all the consumers' demands, the same proportion that the plant and mains necessary to supply this one consumer bears to the total plant, etc., required for all the consumers, therefore a proportion of the total annual standing charges are debited to each consumer in proportion to his mean demand.

In the opinion of the author, this method gives as nearly as possible the fairest division of the standing charges, and it makes substantial allowance for the fact, that the demands of the different consumers do not all coincide in point of time of day. Opportunities are also given for preventing any unusual maximum demand being registered, so as not to penalise the consumers for having parties, etc.

Diversity Factor

Owing to the varying time of day at which the different consumers' heaviest loads are taken from the mains among the fairly large and representative number of consumers at Brighton, the maximum load of the station is now only 66 per cent. of the sum total of the consumers' maximum demands. This want of coincidence in point of time of the consumers' maxima thus means a considerable saving in plant and mains, consequently in the standing charges of the undertaking; therefore the consumers are entitled to the benefit of this, which they get by the Corporation assuming that each kilowatt demanded by a consumer only costs 66 per cent. of the above mentioned £17.9 a year, or £11.8 per annum, which works out to nearly 734d. per day per kilowatt demanded by any

consumer.

Load Factor-Cost Curves

This figure of 734d. per kilowatt, and the previously determined figure of .71d. per unit for running expenses enables the cost of supplying electricity to any consumer in Brighton this year to be very closely ascertained, and from this data the curve of costs, Fig. 3, has been drawn.

The solid line gives the average cost of supplying each unit to a consumer at Brighton in 1895, who used his demand so many hours or fractions of an hour per day on the average throughout the year. The hyperbolic line of dashes shows how rapidly the charge to cover

the standing costs falls as the time of daily use of the demand is lengthened; the total cost curve is obviously obtained from this by adding .71 to it vertically.

Differential Rate

As it was thought impolitic to charge consumers on the true theoretical method of so much per maximum kilowatt demanded,

and so much for the running costs of the units registered by their meters, on the ground that this tariff might possibly have the effect of preventing consumers installing any other lamps than those likely to be constantly used, it was suggested that nearly as fair a charge could be made, by refusing to reduce the highest permissible price per unit consumed, until the individual consumer had paid off all his proportion of the year's standing charges, as determined by the demand indicator, in the manner above described. This system has worked out very well during the last three and a half years, and naturally tends to encourage profitable consumers to use electricity.

From the above calculations it follows, provided all consumers paid 811⁄2d. per unit for the first 365 hours in the year they used their demand, and 3⁄44d. for all units consumed afterwards in that year, the whole of the annual expenditure would be covered, and the Brighton undertaking would be considered in a self-supporting condition. However, there will always be a considerable number of consumers who do not use their demand on the average one hour per day throughout the year, among whom of course must be included a great many of those connected during the year in question, and as the maximum price chargeable at Brighton is fixed at 7d. per unit, it is impossible to charge on this equitable basis. The tariffs adopted for the last three years have been something therefore less fair to the long hour profitable consumer, and by the one now in force each consumer pays 7d. per unit for the first 365 hours in each year he uses his demand and 3d. afterwards. This tariff will doubtless produce sufficient profit during this present year from the units charged at 3d. to people using their demand, say slightly more than 11⁄2 hours per day, to justify a reduction in the 3d. units being very soon made to 2d. per unit.

Short Hour Consumers Not Profitable

The small dotted curves show the average price paid by the Brighton consumers on the present and proposed future tariffs according to the average daily number of hours they individually use their demands.

From an inspection of the tariff and cost curves in Fig. 3, it will be seen that loss was incurred in supplying all consumers at Brighton during 1895 who used their demands less than 600 hours per annum. In connection with these unprofitable consumers, it

may be quite reasonably asked how with a given plant and set of mains it can be said that the undertaking can lose money by having to supply one set of short time consumers while it is making a profit on supplying others with the same commodity, or why selling units at 7d. can be less profitable than not selling them at all. The answer is, that in growing stations, as the author premised should alone be considered, the same expensive extensions and the consequent increase of standing costs are necessitated by having to supply the short time consumers as if they were long hour users, although they probably only use their proportion of the plant say three months out of the twelve; thus they not only cause fresh capital to be spent, the interest, etc., on which they cannot pay off themselves, but they necessitate their unpaid share of the standing charges being paid by the better class of consumers, who could have been supplied from the station in the condition it was in at the end of the year without further extensions having to be made for many years to come; therefore, actually this short time class increase the charges to the profitable, and this is surely only another way of stating that there is loss incurred by having to supply them.

Profit and Loss Account

Given the cost of the standing charges per kilowatt demanded by the consumers, the running costs per unit and the individual demands of all the consumers, it must be obvious that it is then possible to make out an annual Profit and Loss Account showing what profit or loss is made from any class of consumers. The author has prepared such a one for the Brighton undertaking in 1895. He has taken the running costs at 8d. per unit, and has divided the classes of consumers into the four following:—

1. Those who were connected during the year, and of which a great many therefore could not naturally have had enough time to pay off their proportion of the standing charges incurred during the year in providing sufficient additional plant for their probable demands.

2. The consumers who did not consume sufficient electricity to be equivalent to the use of their demand 365 hours or one hour per day on the average.

3. Those who were a source of loss to the undertaking owing to their using their demand less than 11⁄2 hours per day, which was about the minimum time necessary on the present tariff to pay off all the cost of supplying them for that period.