Lifts are really quite efficient especially as they are normally designed with a counterweight so that the main energy usage is lifting extra weight (i.e. you).

Lifts are really quite efficient especially as they are normally designed with a counterweight so that the main energy usage is lifting extra weight (i.e. you). Descending doesn't require added energy (in a simplistic model) as it's using gravity to do the work. To do the maths: * It takes 10 joules to lift 1kg 1m * If we assume each floor is 4m, then 200m needs to be lifted daily * If we assume a 100Kg human then our daily commute requirements are 200,000 Joules -- (200 * 100 * 10). To put this number into other terms that's about 56 Watt Hours - the energy required to run a decent laptop for an hour. Gasoline has ~ 31,500,000 Joules per litre in it it. If we were 10% efficient at using that energy we would need 0.06l of it (0.02 US Gallons).