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Comment by PeterisP | Hacker News Reader

This is a bit of an apples-to-oranges comparison. If you consider the energetic content of the gas burned in a car, then you need to measure the same thing for the EV - large power plants are a bit more efficient than car engines, but unavoidably far from 100%; in order to get 10kwh of electricity to an EV the current grid would burn gas or coal with an energetic content of probably 25kwh or so.

So electrification alone can't bring so large reductions in total energy consumption - it is simply one of the prerequisites for that, and it also needs to be accompanied with large scale build-up of non-fossil electricity, of renewables or nuclear.

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Mackay's book, and this discussion, are in the context of a hypothetical future where Britain is powered predominantly by solar and wind. It's not even that hypothetical anymore, because as you can see from this dashboard(https://www.energydashboard.co.uk/live) the UK is currently getting 75% of its electricity from renewable and low carbon sources. So even today, driving 50km there only requires 15kwh of gross energy.

But when you're using solar to generate the energy, what's the equivalent of burning? I'd argue that it's just "whatever the panel produces". So, if you have some panels producing 1 KWh, and you need that KWh for your car, the relevant efficiency here is transport efficiency.

Since we currently aren't covering the existing demand for electricity with reneweables, the "marginal kwh" of electrifying some car comes from fossil fuels, not solar.

Those are two separate things - electrifying some transportation need gets us X benefit, and converting some electric generation from fossil fuels to solar gets Y benefit, but the former doesn't automagically create the latter.

1) There is no reason to attribute all of the carbon intensity to the last use to be added. It is far more accurate to estimate the carbon intensity of something by the blended production mix at its time of use. Fossil fuel plants are often kept online for factors beyond the need for additional capacity at a certain time.

2) You are assuming there is no curtailment or rejection of wind, solar, and nuclear, which is categorically false. This is why there are time-of-day rates that vary so drastically. There are large amounts of renewable/low-carbon energy that would otherwise be wasted in pretty much every geography.

You could apply that to everything.

If I turn on (or keep on) my light when usage isn't completely covered by renewables, should that be calculated as using all fossil fuels?

The logical extension is that everyone should calculate the carbon intensity as a binary choice which is obviously wrong.

The only reasonable way to go is to look at the actual carbon intensity average.

> equivalent of burning

Probably storing.

Give it 50 years and we're going to be facing some other unexpected global disaster from unchecked battery proliferation.

Hopefully it's less dire than climate change though.

  > If you consider the energetic content of the gas burned in a car, then you need to measure the same thing for the EV

True, but the resulting numerical "hit" for EVs is a lot smaller than for ICE vehicles.

This is largely because

1.) big stationary heat engines are much more efficient than small weight-optimized mobile ones, and

2.) the electricity grid also has some renewable energy mixed in, so a growing fraction of the electricity supply doesn't even need an (energetically imperfect) heat engine.

If you want to include production of electricity you also need to include refining and distribution of gas. So many exclude that and make calculations as if the gas get to the gas station by magic

That’s not true, because the point of comparison is already the _output_ of the electricity generation in TWh. Once the energy is available in the grid you can put it in your EV at almost 1:1.

Additionally, the parent overlooks that while a lower number is estimated, they compare against a hypothetical 2000+ TWh number instead of the tightest 900 TWh estimate.

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