Cost of Electricity

• Amount of energy used in home is measured in kilowatt hours (kWh), also known as Units, where 1 kWh is equal to the energy converted by a 1 kW device for 1 hour.
• 1 kW = 1000 W

  
• 1 hour = 60 minutes - 24 hours in one day

  
• Equation:

  • Units used (kWh) = Power (kW) x time (hours)
• Equation:

  • Cost = Units used x Cost per unit
• If energy = Joules (J) units for…

  • power = watts (W)
  • time = seconds (s)
• If energy = Units (kWh) for electricity bill, units for…

  • power = Kilowatts (kW)
  • time = Hours (h)
• Cost of using an appliances is affected by…

  • its power.
  • the length time in use.
  • the cost of each unit of energy.
• Efficiency of a device is shown on scales, the more efficient a device, the better the rating will be - important as help compare devices that do the same thing.
• Working out how much money you save you must consider:

  • initial cost.
  • cost of electricity for each unit.
  • government feed-in tariffs
• • payback time = cost / saving