18-20 TW is somewhat more than the current 16 TW, of which renewables (mostly large hydro) account for about 9%.

Read the articles I wrote :)

Our current energy use is about 15,500GW. Electricity is 2,000GW of that, very little of it renewable, and the renewable chunk mostly hydro with little capacity for expansion.

The current fossil fuel electricity generation has to all go. I mean, just deforestation contributes 18% or so of all greenhouse gases, and we need to drop to 10% of current emissions by 2050 to avoid whacking past 350ppm CO_2e (more or less, depending which recent paper you believe). There's just no room in that emissions budget for burning coal to warm supermarkets which are being cooled by open fridges, and stuff like that.

Any serious mitigation plan requires that we abolish burning fossil fuels for electricity.

Kudos to [anyone]'s post above.

A problem I see in many above is failing to account for capacity factors. 5 TW of wind or solar generation won't give you 5 x 8,760 hr/yr kwh/yr of electricity, but more likely 5 x (8,760 * .25) kwh/yr.

In central Europe a 2 person household can easily live with less than 1000 kWh electricity per year (using efficient lamps, efficient fridges etc.).

Is that relevant? You can probably remove most energy needs in any small specific location by importing stuff with lots of sunk energy in them. Kiashu talked about total energy needs per capita, not just electricty in our homes.

photovoltaic factories from Oerlikon

Only $2000/kW nameplate PV? That's nice, but with lower capacity factor than wind at similar costs per kW, what's the use?

How do you end up with 2 kW?

Remember that only around one-third of electricity use is for domestic purposes. The other two-thirds is factories, streetlights, food processing, heart-lung machines, computers in libraries, and so on.

Presumably we'll want something beyond our own homes. Assuming all our energy use is renewable, and assuming we seek out efficiencies wherever we can find them, 2kW may be enough for a decent lifestyle.

You should have a good look at all the things which use electricity today, and all the things which use fossil fuels, and then imagine making all the fossil fuel use into renewable energy instead - it's a big deal.

Doable, but not easy.

Yes, it's more electricity use than most countries currently have. But bear in mind that it's also electricity in place of other energies. Worldwide, we use 15.5TW of energy generally, but only 2TW of that is electrical. So in fact I'm suggesting a decline in overall energy use to 2kW per person, and a large increase in electricity use. That's worldwide; the picture for individual countries will of course be different.

I'm using no arbitrary ratios, as you'll see from the original articles I referred to above. I know some people don't like clicking links and reading articles off a particular site, but it seems better to link and then assume people read the article than to reproduce the entire article in full in a comment.

Of course there's a lot of room to move in these sorts of estimates. I've no doubt that if 2,000kW were available to people, they'd find ways to use it up; likewise, if we had 0.5kW, we'd manage to live tolerable lives. However, what's clear is that if we want to have an entirely renewable society, that's going to be a big build-out and take some time. We'll need more renewables than we have all electricity now, and we'll need lots of other things built, too - railways and so on.

The expense doesn't worry me, because we build things all the time. Often in these discussions the billions for renewables or rail or whatever are presented on their own, so they look very expensive. But we're always tearing up old power stations and roads and power lines and so on, and building new ones in their place. To take examples from Australia, it could be $55 million/km highways to carry 2,000 people an hour (EastLink), or $13 million/km railways to carry 20,000 people an hour (Perth).

Look at $13 million/km on its own, it looks terrible. Compared with $55 million/km, not so bad. Add in that it carries ten times as many people, and it looks really good. But someone who wanted to ensure no railways were built would focus on the $13 million/km. This is the sort of thing Gail has done here with wind turbines, focusing on the costs without comparing them to other costly things, and without considering the relative benefits.

So the question is not whether we'll build things, but what we'll build.

Is wind power more expensive than coal or gas? Sometimes yes, sometimes no - let's say it's more expensive. But wind power will still have "fuel" for itself twenty years from now, coal and gas, maybe not. So then the extra you pay for the wind looks not so bad. But wind is intermittent? Well, that's why we have a grid, and why we have solar, geothermal and so on.

If you want to make a thing look bad, talk about its cost, talk about it in isolation, and never speak of its benefits. You can do this with wind, coal, nuclear, solar, whatever. It's more honest and decent to look for a more balanced overview of things.

We can build all these renewables, but we have to decide to do it, and keep the resolve across many countries and through changes of government in each of those countries. It'll never be perfect. But then, the current fossil fuel system isn't perfect, either. Large chunks of the world population are without powered transport or electricity. Luckily, it doesn't have to be perfect, just overall in the right direction.

And that's another trick played by those against something - point out it can never be perfect, hold it to higher standards than anything they support is held to, and once it's shown it's imperfect, condemn it utterly.

So 2kW is not a terrible figure, but it's very likely too high. If you're going to assume quite a few efficiency increases - and you seem to - then 1kW is probably a better estimate, and 2kW represents a luxurious lifestyle. Electricity is astonishingly more useful than thermal energy.

Going from 0kw to 1kw certainly improves one's lot more than going from 1kw to 2kw.