There were 40,136 street lamps in service in Chicago on January 1 of this year, 38,240 being the average throughout the year, as is shown below: Take the largest item of 15,930 450-watt, municipal arcs at an average of $56.13 as an example of what has been accomplished in Chicago by purchasing electrical energy from the Sanitary District of Chicago (a municipal corporation) and operating a municipally owned distribution lighting system. The total cost of $56.13 per arc per year consists of $31.32 cash costs and $24.81 fixed charges, which includes interest, depreciation, taxes and rent. The cash costs of $31.32 per arc lamp per year are made up as follows: Sanitary District power including the operation of sub-stations.. Maintenance and repairs of circuits and arc lamps (includ- Totals...... It is very evident from the above items that the electrical energy which amounts to 36.6 per cent of the total cash cost is being supplied at a relatively low rate while the operating labor, 42.2 per cent of the total, is relatively high to that of most cities. The electrical energy is contracted for at $15 per horsepower per year delivered to the sub-stations, which, under our operating conditions, means approximately one-half cent per kilowatt hour. A high union scale of wages is paid all municipal electrical workers in Chicago, including linemen at $5 per day, arc lamp trimmers $100 per month and line repairers at $155 per month. A study of these factors which make up the cash costs leads one to believe that there should be no reason for cities contracting with electrical utility companies for 450-watt arc lamps at $90 to $100 per year, unless the fixed charges on the installation more than double that in Chicago, as most public utility employes are not paid as high a scale of wages. Chicago's investment per arc light on the underground distribution system amounts to approximately $510.80, which is the present estimated cost of installing flame arc lamps in downtown streets, laying 4 duct tile, with laterals for 23 lamps to the mile of street. It includes also, besides the underground construction, repaving, sub-station, post, lamp, complete ready to light up. The present average investment of the Chicago Municipal Lighting System for lamps now operating on underground circuits is $316 per lamp. The investment for the overhead lighting arc system is approximately $215.60 per arc, making an average investment of $256 per arc throughout the system. I know of no electric utility corporation paying as high a scale of wages as the city of Chicago for operating and maintaining its lighting system, and still there are no cities in the country operating under similar local conditions that contract for anywhere near as low rates, but generally 40 to 50 per cent higher. The city of Chicago makes yearly contracts with the Commonwealth Edison Company for 450-watt flaming arc lamps at $75 per year for the outlying districts where the lamps are sparsely installed (averaging 500 feet apart) which results in greater investment and higher annual maintenance costs than if spaced an average of 250 feet apart, as are the municipal arcs. Ten thousand and forty-four of the 17,493 municipal arcs were of the 10 ampere, flaming arc type, 1,261 9.6 ampere, open arcs and the balance of 6,188 being 7 ampere, enclosed carbon arc lamps. The 1,261 open arcs have lately been replaced by 300-watt nitrogen tungsten lamps. Nitrogen Tungsten vs. Flaming Arcs About six months ago, after a thorough investigation, we decided to discontinue installing 450-watt flaming arc lamps and to install in their stead 20 ampere, 300-watt nitrogen tungsten lamps. The favorable results obtained so far from the 1,800 which were installed two months ago lead me to believe that this 300-watt, 600-candle power, nitrogen tungsten lamp, which gives an equivalent illumination to that of the 450-watt flaming arc after the flamer has been in service a short time, is the most economical high power open street illuminant on the market today. When the slagging of the carbons and the etching of the inner globe of the flaming arc are eliminated the arc should be a strong competitor of the nitrogen lamp. The nitrogen lamps which are purchased under a guarantee of 1,000 hours' life make a more flexible operating system, give a more uniform light and cost less to install and maintain under our Chicago local conditions. It is planned to replace within the next two years the 6,188 7 ampere 450-watt enclosed lamps (giving only about 250 candlepower) with the 300-watt, 600-candlepower nitrogen tungsten lamps, and to extend the system with 5,000 additional lights of this type. The largest saving in operating the nitrogen lamp under our local labor conditions lies in the trimming and patrolling item. This saving is brought about by allowing 700 to 800 nitrogen lamps to be kept in repair, cleaned and patrolled by a patrolman who is allowed, besides his salary of $100 per month, $3.75 per day for the expense of an automobile supplied by himself to aid in his work, instead of a trimmer at $100 per month, trimming 330 arcs, and a patrolman at the same wage patrolling 500 arcs, which averages approximately 200 arcs per man for trimming and patrolling, making the relative saving 45 per cent for this item. Although the cost for four nitrogen tungsten renewals per year (which the manufacturer guarantees not to exceed) is nearly three times the annual cost for flame arc carbons, the relative saving in such items as the cost of power and fixed charges in the nitrogen installation more than offsets this high cost for lamp renewals. It is very probable that the life of these 20 ampere, 300-watt nitrogen lamps will, within a short time, materially exceed the present guaranteed 1,000 hour life, which would result in a still greater saving over that of the flaming arc. Electric Tungsten Residence Street Lighting Nearly 100 miles of our best residence streets, which were formerly lighted with 50-candlepower gas lamps, have been relighted during the last two years with an underground, 4 ampere, 80-candlepower series lamp system, at a reduced annual expense per unit. A large saving was made in this installation by staggering the old gas lamp posts 150 feet apart on each side of the street and wiring them. Street Subway Lighting Over 400 street subways running under railway tracks have been lighted by the electrical department during the last 18 months, at an installation cost averaging $10 per 20-candlepower tungsten lamp. The standard spacing of these lamps averages one per 400 square feet over the roadway, and one per 200 square feet over the sidewalk area, which makes a well lighted subway. The Commonwealth Edison Company supplies the energy, renews and maintains these lights under a 5-year contract ordinance and allows credit for all outage of the lamps, at $6 per lamp per year. Contract Lighting Rates The 5-year contract ordinance which was passed by the City Council November 26, 1913, after a thorough investigation made by the city authorities of the Commonwealth Edison Company's books, gives a relatively lower schedule of rates for various kinds of electric service than any of the larger cities obtain by contract, except those being supplied by current generated by water power. The table below gives the relative retail electric lighting rates of electric companies in the largest cities, based upon 24 hours' use per day of the maximum demand, which is the average for Chicago conditions: Min. monthly None None $1-except $.50 $9 per year None $12 per year In all of the above cities carbon incandescent lamps are renewed free, except Buffalo and San Francisco. (The above is based on 1 kilowatt load used 24 hours per day.) The two principal causes for these low rates in Chicago are the efficient generating units installed in the large central stations and the high load factor on the stations and system. The load factor has been materially increased by the sale of the power to the street surface and elevated railway lines. During the year 1913, 929,000,000 kilowatt hours were generated by the Edison Company. The total annual expense of the company for the year was $10,858,343.26, consisting of $7,957,299.99 cash costs, $1,547,127.44 depreciation and $1,353,915.83 taxes and municipal compensation. This shows a total cost of approximately $1.17 per kilowatt hour generated and distributed into the lines during the year. Gas and Gasoline Lighting While many gas lamps are being replaced in Chicago by electric lamps each year, many gas lamps are replacing the uneconomical gasoline lamps in the outlying territory where the gas mains have been extended. The only expense to the city involved in extending gas services and erecting the gas posts is that for paving over the services. As this amounts to an average of less than $5 per lamp, a large saving is made by replacing the gasoline lamps with gas lamps where the gas mains are laid. |