this is a formula that Bill Gates proposes in his TED talk about achieving zero emissions.... One of those factors must get close to zero. I was made aware of this TED talk by a conspiracy theory video that pointed out that it sounds like Bill is suggesting we could reduce population (the first factor P) by 10% with vaccines. His concern for these low income people seems to be his goal so I don't think that was the intended meaning but rather just saying that vaccines will result in an increase in population instead of a decrease.
S is for services per person. This was dismissed without anything but a graph showing energy use going up rapidly. This is the area I want to work on as an anarchist. If we need electricity or other energy purchase, we need money to do so and we remain slaves to money and the jobs to get money and the government and banks to keep that money valuable. 42% of USA energy use goes into heating and cooling of buildings. With PassivHaus standards, that can be reduced by 90% simply with insulation, air-tight walls, and use of a heat recovery ventilation (HRV) or energy recovery ventilation (ERV) system. The remaining 10% can also be eliminated with more of the same or passive heating technology or thermal heat/cool storage or a little bit of renewable energy.
E is for efficiency. The worst offenders of efficiency are energy transmission and batteries (and other energy storage). Bill mentions the need for a battery "miracle" but dismisses them as too little too late. What is not entertained is the use of energy storage at the point of use. Point-of-use batteries or thermal storage or pressurized air will greatly reduce the need for transportation of energy and the volume of energy being transported at any point in time (assuming a slow recharging of the storage). Wattage of the heat loss is the square of the current times the resistance. This means that if you have half the amperage through transmission wires, you will have a quarter as much loss of energy in that wire (1/2 squared is 1/4 and the resistance stays the same).
The last factor is carbon per energy used which is where Bill assumes is the only place for "miracle" inventions. This is where using depleted uranium for new nuclear power is the goal of the research he is funding. I commend this goal given my lack of confidence in people catching on to reducing the other three factors (don't produce kids, reduce your energy needs, use energy efficiently with more localized storage and localized energy production). The problem of course is we will still need to buy that nuclear-sourced energy.