How many "Energy Servants" do you use?
Energy Servant – David MacKay in his book “Sustainable Energy – Without The Hot Air” – worked out kWh equivalents for daily activities, heating & cooling, domestic jobs, and having fun. He also estimated 1 kWh being equal to one hour of a human servant working for you.
Kids Activity – read through this Energy Summary and ask your kids to draw a picture of the servants needed for some of these.
Daily Life —————————————
Home
Taking a bath uses about 5 kWh, but a shower (30 litres) uses about 1.4 kWh.
Using a mix of kettle, microwave and oven – 3 kWh/d
Using a washing machine and line drying – 1 kWh/d
Refrigerator/freezer – 2.5 kWh/d
Heating and Cooling using efficient reverse cycle system – 3.6 kWh/d
Using a mix of kettle, microwave and oven – 3 kWh/d
Using a washing machine and line drying – 1 kWh/d
Refrigerator/freezer – 2.5 kWh/d
Heating and Cooling using efficient reverse cycle system – 3.6 kWh/d
[ Home Energy Use – 10.6 kWh/day ]
plus:
Business ( mix of hot water, general power & heat ) – 8.4 kWh/day
plus:
Lighting
Estimating a mix of high and low energy bulbs,
plus a very small contribution from outside lighting and advertising – 4 kWh/day
plus:
Technology
Computers, TVs, chargers on stand by – serious users of electricity – 4 kWh/day
Total Daily Life Energy Use – 27 kWh/day
Food and Farming
A normal diet of 2600 calories a day is around 3 kWh/d per person
A vegan growing their own food can match this, but for the rest there are add-ons
Plus Food Production – Milk & Cheese adds 1.5 kWh/d , Eggs add 1 kWh/d ,
Meat adds around 8 kWh/d , add in family pets – 2 kWh/d
Example Extra Energy Use to Feed Us – 15 kWh/day
Stuff Used & Consumed
Aluminium cans and plastic water bottles – 3 kWh/d
Packaging around food and other items – 4 kWh/d ,
A new computer or TV every 2 years – 2.5 kWh/d ,
Using two AA batteries a month – 0.1 kWh/d
One daily newspaper 2kWh/d , but if recycled – 1 kWh/d
Cost of building and maintaining roads – 2 kWh/d
Desalinated water – 1.3 kWh/d Sewerage treatment – 0.4 kWh/day
Example Energy Use for Other Things Daily – 13+ kWh/day
Transport ————————————-
Cars
Energy per unit of fuel for diesel (10.7) or petrol (9.7) is – 10 kWh/litre
(also called the calorific value or energy density)
Energy /day = 50 km/day x 10 kWh/litre = 30 kWh/day
16.67 km/litre ( or 6 lt/100km)
or 30 servants carrying you to work and back!
Note: Efficiencies – to go twice as fast needs eight times to engine power,
halving your driving speed can reduce your fuel use by 75%
Consider the Options
Cars – 80 kWh/100 km,
Bikes – 1 kWh/100km,
Trains – 1.6 kWh/100km
Buses – 7 kWh/100km,
Metro/Trams – 4. 4 kWh/100km
Electric vehicles – 10-22 kWh/100km
Planes
Energy per unit of aviation fuel is – 10 kWh/litre
(also called the calorific value or energy density)
Energy /day = one long haul a year x 10 kWh/litre = 65 kWh/day
420 passengers (24,000 kWh/day of the trip )
or 65 servants waiting to carry you to Europe and back once a year.