Which uses more energy: flying to the Canaries for a week or turning the temperature up at home?
We can make some back-of-the envelope estimates to get an idea of the comparative fuel use. We can assume the Canaries to be 3500 km away, so a 7000 km round trip. From Wikipedia we find that an Airbus A320 carries 24210 litres of fuel and has a maximum range of 6000 km with 164 passengers, that means a lowest fuel consumption figure of 2.5 litres per passenger per 100 km 1. Other sources such as the Economist on 2006-06-10 give a typical flight as 3.5 L/pass.100km. Let's take the average of the two and say 3 L/pass.100km 2.
Now let's assume we are two people and the plane is full, so our share of the plane's fuel for the 7000 km is 420 litres. We can look up how much energy that represents, which is 35 MJ/L for aviation fuel, so a total energy usage of 14700 MJ. That's the same as 4063 units (kWh or kilowatt hours) of electricity or gas used to heat our house.
Incidentally, that 420 litres of fuel, if it had been taxed at road fuel rates, would have cost around 600£; how can air fares be so cheap?
Now in our little house, we burn around 8000 units of gas for space heating each year (that's calculated by taking 4 times the summer bill, when we have no space heating, from the total for the year). So this one flight to the Canaries and back uses in one go the same energy as it takes to heat the house for half a year. We would have to shut the house down and stay away most of the winter to benefit from saving heating bills.
How much does increasing the temperature cost? It depends on a lot of factors of course, but for a very rough guess based on Newton's law of cooling with an average temperature difference between inside and out of 15C, every extra 1C would add about 6% to consumption, and an extra 5C very roughly a 30% increase. That 30% increase would be for us 2400 units, a lot less than our trip would use.
So in terms of energy use, putting our room temperature up 5 C throughout the winter would use not much more that half the raw energy taken by one holiday for two in the Canaries.
Of course there are huge variations in conditions. The rules change completely if the heating is electric as then a lot of energy is wasted at the power station. A closer holiday destination would use less energy, but perhaps not reach somewhere warm enough not to still need heating. A bigger party makes the flight usage worse, a single person makes it better. It's worse if the plane is not full.
nib 2014-10-26
[1] We use that odd-looking unit because it makes it easy to compare with a car; my little diesel burns 5 litres per 100 km (L/100km) so with just me in it uses twice as much as the aeroplane per seat, with 4 people the consumption of the car is half of the plane's per 4 seats.
[2] The fuel consumption of jet aircraft has improved a lot since they were introduced, and they have almost caught up with the slow turbo-prop aircraft of the 1950s that they displaced, however Concorde used 16.6 L/pass.100km or more than five times as much fuel per passenger as a typical modern sardine tin.