Cost calculations
Electrical power
Electrical power is the rate at which electrical energy is supplied as power specifically electrical power. One kilowatt (kW)=1000W. One watt of power is equivalent to one joule of energy (1 J) that is supplied for one second (1 s). The power consumption of electrical lights and other electrical devices is therfore an indication of the rate at which energy is being converted in those devices. In a 60W light, 60 J of electrical energy per second (every second) is converted to heat energy and light. In a 2kW heater 2000 J of electrical energy is converted in each second to heat energy (and a small amount of light energy).
Formula for power
Power=energy/time
Paying for electricity
An electrical meter where consumers pay their municipality or Eskom monthly. The meter is read every month, and the consumer is charged for the quantity of electricity that was used. A prepaid meter where consuers buy a voucher (electricity coupon) for a particular quantity of electrical energy. A code number is fed into the meter in order to download the electricity (as one does when loading airtime into a cell phone). As soon as quantity has been used up, the electricity switches off. Consumers pay for the amount of electrical power that they use. The amount of electrical energy they use is measured in kWh (kilowatt hours). A kilowatt hour is the energy that is being supplied when 1000 watt works for 1 hour. An electric meter marked off in kWh measure household energy. When we pay for electricity, we pay a 'unit price' , i.e. a price per kWh.
Formula for cost of electricity
cost=power(powerconsumption) of a device (in kWh) x time (in hours) x unit price
Alternative devices and systems
The geyser uses most of the electricity. By installing solar panels with solar geysers for the heating of the water, much money may be saved. It also saves electricity if you switch off the geysser during the day. There are also various devices that work with solar panels, e.g. freezers, fans, television, electric lights. Flourescent lamps (energy savers) and LED light bulbs are just as bright as ordinary light bulbs, but use much less energy.