By Mike Pepler, Ashden UK Awards Manager

This is the first of a two-part blog that looks at the changing relationship between energy, money and food.

The cost of energy has been increasingly in the news in the UK. Rising transport fuel prices caused protests in September 2000 – though prices are now 50% higher than they were at that time. Rising gas, electricity and heating oil prices have also been a cause for complaint, especially during the cold winter of 2010/11.

So just how expensive is our energy? A few numbers…

• A litre of petrol contains about 9.4 kWh of chemical energy and currently costs just over £1.35 in the UK, or 14.4p/kWh.
• For comparison, a litre of diesel contains about 10.9 kWh and costs about £1.40, or 12.8p/kWh.
• When it comes to domestic energy, natural gas is currently around 4.7p/kWh and electricity is 13.2p/kWh.

Taxes obviously play a part in these prices, with domestic energy just paying 5% VAT, while transport fuel attracts a duty of 59.95p/litre and 20% VAT on top of that.

So the question is, what is a kWh of energy really worth? Here are some examples:

1 kWh of petrol will

• move a small, efficient car about 1.3 miles
• allow about 40 minutes’ use of a small chainsaw – producing many times this amount of energy in wood for heating

1kWh of electricity will:

• Run a washing machine through a single cycle
• Run a hairdryer for 40 minutes
• Run a laptop computer for 40 hours
• Run a 15W low energy light bulb for 67 hours
• Run an electric bike for 100 miles (with some pedalling too)

1 kWh of human effort is equivalent to:

• Two hours for a top professional male cyclist on a time trial.
• Ten to twelve hours of hard physical work for a man.

1kWh of effort from a bullock is equivalent to:

• Two hours of work (at a rate that can be sustained for eight hours)

Of course, before we had fossil fuels, if you wanted a few kWh of work from a bullock you needed to provide sufficient food and water for it to do the work. Likewise, if you were going to hire a man to do some physical work, you would at least have to pay him enough to eat and drink, but in practice more than that to cover other living costs. Of course, in countries where fossil fuels are less affordable or accessible, these considerations still apply.

But for most of us in the UK, of course, the industrial revolution transformed our relationship between energy, money and food... Part two of this blog looks at how this relationship has changed, and where it might be going in future.