Rebound Effect

(N.B. Obviously there is the excellent UKERC report on the rebound effect but don't tell anyone that I actually haven't read it fully, so I might just be repeating what they've said.)

While looking at MacKay's book, one point of discussion that came up was what would be the level of demand in the future. MacKay considered efficiency improvements in electrifying transport and heating, as well as having no electricity conversion losses, bringing demand from 125kWh per day per person down to 68.

Certainly this is possible, however we all know that improvements in energy efficiency can be cancelled out to some degree by increases in energy usage (the rebound effect). So I was thinking whether this would mean 68kWh/d/p is realistically possible and to what extent the rebound effect might reach.

Considering the direct rebound effect (e.g. engine efficiency improvements lead to driving more), I wonder if there are limits to it. For example:

• Insulating your house means you use and spend less on keeping your home warm. However if your home is already at 20 degrees before insulation you're not going to want more heat, so the rebound effect would be small (e.g. only from those in fuel poverty, who don't already have their homes at a comfortable temperature).
  
• Using electric cars rather than internal combustion may bring large energy savings. Although more people would be able to commute further or go on leisure trips more often, there is a limit to how much more driving people need, want or can do. People would obviously tire of 3 hour commutes, have only so much free time for other activities such as shopping and the average occupancy can only drop from 1.6 to 1.
  
• More efficient light bulbs means using and spending less on lighting. There is a limit to how much more lighting someone could want (lighting on all day in every room) and as most people don't currently go around in darkness, the rebound effect would probably also be quite small.
• and so on.

UKERC does estimate that these direct rebound effects might reach only 10-30% so obviously the question shifts to indirect rebound effects (e.g. money saved from fuel costs goes on a transatlantic flight).

Indirect rebound effects are harder to predict because of the multitude of economy-wide effects on different levels, so I'll just say to go read the UKERC report, and that they estimate it can often be over 50% of the reduction or even greater than 100%.

So this suggests that - in a developed country - reductions of energy use in the major categories: transport (domestic at least) and heating, could well reach the estimate of MacKay. However economic growth and the indirect rebound effect could see other sectors, I'd guess most likely electrical goods, would struggle and may well increase.

Considering that energy use (globally or otherwise) has only fallen noticably during recessions (and then by only a few percent) it does seem difficult to see a self-imposed drop from 125kWh/d/p to 100 let alone 68.

Although never say never.