Thu, 29 Jun 2017 13:57:47 +0000
In its preamble when ZESCO was proposing a tariff increase it said: “ZESCO is cognisant of the fact that Zambian citizens have varying income and expenditure patterns. In seeking to mitigate the impact of the tariff increase on households, the R1 tariff which currently stands at K 0.15/kWh has been maintained. Furthermore, the R1 tariff band limit has been increased from 100kWh to 300kWh per month. This means that customers consuming up to 300 units of electricity in each month, will pay only K 0.15/kWh (excluding monthly fixed charge and taxes).
Our assessment indicates that lower income customers who are using electricity for lighting, TV, radio and other basic electrical appliances will consume less than 300 kWh. This implies that by expanding the R1 tariff band from 100 to 300 kWh, and maintaining the tariff at K0.15/kWh, the majority of the lower income customers will not incur an increase in their cost of electricity despite these proposed increases.
Further, the proposed residential tariff structure gives each Zambian household the opportunity to plan and control its expenditure on electricity. Keeping consumption to the lowest tariff band (R1) possible and implementing energy saving practices such as those publicised by ZESCO through the Switch and Save, and CFL Bulb replacement campaigns can cushion the impact of tariff adjustments on any Zambian household.”
It was in November, 1963, when I heard that President John F. Kennedy had been assassinated through the older guys in my class in Standard Six who had access to newspapers at Kankoyo Primary School in Mufulira. We were all stunned as if we had lost a close relative which cannot be said about some presidents I know, whose names I won’t mention here. One of his famous quotes which has remained with me to this day is: “My fellow Americans, ask not what your country can do for you, ask what you can do for your country.” Paraphrasing, “My fellow readers ask not what ZESCO can do for you, ask what you can do for ZESCO to minimise load shedding.”
The other one is: “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard.” Indeed adopting energy conservation measures is not easy because it involves breaking old habits that have been formed over decades as a result of cheap electricity such as not switching off the lights in rooms that are not in use.
ZESCO says keeping consumption to the lowest tariff band (R1) possible and implementing energy saving practices such as those publicised by ZESCO through the Switch and Save, and CFL Bulb replacement campaigns can cushion the impact of tariff adjustments on any Zambian household but do not say how much can be saved. It is not enough just to say boil water in a kettle and not on a stove.
I have earlier attempted to quantify (to express in numbers) how much power can be saved if all electrified households in Zambia switched to CFL bulbs in an earlier article. I have also expressed in numbers how much money can be saved by switching from an incandescent bulb to a CFL bulb.
As I have said earlier before, it was in 1969 when I was doing first year Physics with a view of entering the School of Engineering at the University of Zambia the following year that I came across a quote from Lord Kelvin, an Irish Physicist and Engineer, who said, “When you can measure what you are speaking about and express it in numbers, you know something about it, when you cannot express it numbers, your knowledge is of a meagre and unsatisfactory kind.”
I will now try to explain in numbers how the expenditure on electricity can be planned and controlled.
All household appliances are rated in watts or kilowatts. This will indicate how much electricity the appliance uses in a certain amount of time. For example, a 1kW kitchen appliance uses one unit of electricity in an hour. A 100 watt light bulb uses one unit of electricity every 10 hours, i.e. 100W x10 hours=1000Wh or 1kWh or 1 unit of electricity. Usually the rating is shown on the appliance and the higher the rating, the more electricity it will use.
Power represents the RATE at which electric energy is being fed to an appliance. Note that the power is properly zero if the voltage across the appliance is zero – which is true when it is switched OFF and not when it switched off and is then left in standby mode. Standby mode electricity is a subject of another article. Fortunately, most electric appliances have labels that give their power ratings, and it is not necessary to know the electric currents flowing through them to calculate their power requirements. Furthermore, the VOLTAGE supplied to most household appliances is 230 volts, so Power = (230 volts) x (CURRENT in amps).
From this equation, it is clear that higher power appliances require more current in amps. This is why the main circuit breaker at the distribution board for a geyser is higher than that for lights. The current can be measured with a digital clamp meter if it becomes necessary. It is available at hardware stores such as the newly opened Ingco in Lumumba Road.
For example if the current through a household light bulb is 0.25 amperes and the voltage across its filament is the common 230 volts, then its power is (0.25 amperes) x (230 volts) = 60 ampere volts = 60 watts in a direct current system. Note: 1 amp x1 volt is defined to be 1 watt.
Alternatively a wattmeter can be used to measure electrical power. I am not sure if it is available in Zambia but inexpensive plug-in wattmeters, sometimes described as energy monitors, are available from prices of around US$10 in other countries such as the USA. I would therefore urge local hardware stores to import it as it is a useful instrument in monitoring energy or electricity consumption.
The electric energy, in kilowatt hours (kWh), used by an appliance over a time interval is
Energy (kWh) =POWER (watts) xTIME (hr) divided by 1000
For example: The electric energy used by a 100 watt light bulb operating for 24 hours is (100 watts) x (24 hours) / (1000 watt hours/kWh) = 2.4 kWh. The typical cost of 1 kWh of electric energy from ZESCO in the so-called R1 band is K0.15
Therefore 2.4 x 0.15 = K0.36
Electrical energy is sold in units called kilowatt-hours (kWh), a measure of the energy consumption.
1 kWh is the energy used by a 1000 W appliance in 1 hour.
ZESCO sells electricity using tiered tariffs, like most power utilities, to discourage people from using too much electricity.
We can calculate the cost of using a single appliance by multiplying the power rating by the number of hours and the unit cost of electricity.
Determining how much electricity your appliances and home electronics use can help you understand how much money you are spending to use them.
If you know about how much you use an appliance every day, you can roughly estimate the number of hours it runs. For example, if you know you normally watch about 4 hours of television every day, you can use that number. To estimate the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three. Refrigerators, although turned “on” all the time, actually cycle on and off as needed to maintain interior temperatures.
Find the wattage of the product. The wattage of most appliances is usually stamped on the bottom or back of the appliance, or on its nameplate. The wattage listed is the maximum power drawn by the appliance. Many appliances have a range of settings, so the actual amount of power an appliance may consume depends on the setting being used. For example, a radio set at high volume uses more power than one set at low volume. A fan set at a higher speed uses more power than one set at a lower speed.
Multiply the appliance ampere usage by the appliance voltage usage.
If the wattage is not listed on the appliance, you can still estimate it by finding the electrical current drawn (in amperes) and multiplying that by the voltage used by the appliance. – Use online sources to find typical wattages or the wattage of specific products you are considering purchasing.
Examples: Kettle
- Estimate of time used: The kettle is used several times per day, for about 1 total hour.
- Wattage: The wattage is on the label and is listed at 1500 W.
- Daily energy consumption:
(1,500 W × 1) ÷ 1,000 = 1.5 kWh
- Monthly energy consumption: The kettle is used almost every day of the month.
1.5 kWh × 30 = 45 kWh
Find the daily energy consumption using the following formula:
(Wattage × Hours Used Per Day) ÷ 1000 = Daily Kilowatt-hour (kWh) consumption
You have now arrived at the daily Kilowatt-hour consumption. However, some appliances are not used every day. For example you do not iron clothes every day of the month but you probably cook food every day of the month. Estimate the number of days you use the appliance in a month.
Armed with this knowledge we have now acquired, let us check out the statement by ZESCO that lower income customers who are using electricity for lighting, TV, radio and other basic electrical appliances will consume less than 300 kWh.
From table 2 it is quite clear that the ZESCO statement on the consumption of electricity by lower income customers is by and large a fair assessment. It is also clear from the table that the biggest consumer of electricity is the electric 2-plate stove and in order to avoid the R2 tariff in which the tariff has been increased some people may opt to use charcoal. If you also opt to use 7x60W incandescent bulbs instead of the 7×10 CFLS bulbs, the consumption will go up by 7x60W x 6hours x 30 days divided by 1000 which is 76 units minus 13units for CFL bulbs = 63units, which is a saving of 63/372×100% or 17% achieved through the use of CFL bulbs. Not a small amount by any stretch of the imagination.
