IP Which appliance? © Oxford University Press 2011 Which appliance?

IP Which appliance? © Oxford University Press 2011 The power rating and the new efficiency rating label on devices can be very important to you and the environment. If you needed to buy a new fridge and you had the choice of these two models which would you choose (assuming electricity costs 12p per unit)? Total Cost = purchase price + lifetime energy cost. Fridge 1 = × 105 × 0.12 = £353 Fridge 2 = × 270 × 0.12 = £382 Even though Fridge 2 is cheaper to purchase from the shop Fridge 1 will save you money over its lifetime. It will also save energy – over 800 units of electricity in its lifetime. This will help the environment as there is less wasted energy and less CO 2 emission. Fridge 1 Make: Fridgomatic 50 Size: 0.2 cubic metres Efficiency Rating: A++ Price: £290 Energy consumption: 105 units per year Expected life: 5 yrs Fridge 1 Make: Fridgomatic 50 Size: 0.2 cubic metres Efficiency Rating: A++ Price: £290 Energy consumption: 105 units per year Expected life: 5 yrs Fridge 2 Make: Freezing 12 Size: 0.25 cubic metres Efficiency Rating: B Price: £220 Energy consumption: 270 units per year Expected life: 5 yrs Fridge 2 Make: Freezing 12 Size: 0.25 cubic metres Efficiency Rating: B Price: £220 Energy consumption: 270 units per year Expected life: 5 yrs

IP Which appliance? © Oxford University Press 2011 Should you buy a 100 W filament bulb or an equivalent 20 W compact fluorescent bulb? The details for each bulb are shown below: filamentcompact fluorescent Life of bulb1 000 hrs hrs Cost75p£1.50 Assume an electrical unit costs 12p. Remember: 1 unit = 1 kilowatt hour Total Cost = purchase price + lifetime energy cost. To compare properly we need to look at hours of light and therefore 10 filament bulbs. Filament bulb cost = 75 × × 0.1 × 12 = £ Compact fluorescent cost = × 0.02 × 12 = £25.50 It is obvious that you should pick the compact fluorescent bulbs.