> As of 2021, German primary energy consumption amounted to 12,193 Petajoule, with more than 75% coming from fossil sources, 6.2% from nuclear energy and 16.1% from renewables.

You might offset that 6% nuclear that is going away with renewables if you really put your hearts into it, but probably not. Won't be economical.

Most primary energy is wasted as heat when turning it into electricity. The German electrification program means they'll only need about a third of that power from renewables to travel the same distance in cars or heat the same homes.

Waste heat from a power plant in one part of the country can't be sent to heat homes in another. That's the very heart of the matter.

If you could magically get the angry pixies into all the forthcoming electric cars directly with no waste, sure.

It is very nice milestone that the top line numbers are there already, but way too early to declare victory.

By definition, the primary energy input and electrical energy output are equal for renewable sources that don't require fuel.

So the point is that transitioning from thermal electricity generation to sources like solar and wind already reduces the primary energy use.

Electrifying traffic further reduces the primary energy use, as 100% of primary energy from gas turn into something like 40% of power which can be used to drive the car forward. An electric engine is a lot more efficient.

This is just math and doesn't yet include efficiency gains through insulation, heat pumps etc.

> By definition, the primary energy input and electrical energy output are equal for renewable sources that don't require fuel.

When you think about it, this is unfairly disadvantaging renewables due to an unfortunate choice of primary energy. For renewables, the primary energy is solar radiation! Suddenly the primary energy of solar panels would go up 5 fold just because of changing the definition of primary energy. Then everyone would be talking how unfair primary energy is to fossil fuels.

You can go even further. All "natural" processes are completely excluded from primary energy use.

If you include the energy used by agriculture (as in: photosynthesis) you will get a number that human energy use is something like 99% powered by the sun.

If you include ambient heat, non-solar energy sources become a rounding error. This may seem obvious and silly, but especially in residential heating using the ambient heat with heat-pumps, solar collectors, large sun-facing triple insulated window fronts, will be key for energy usage reduction.

I would recommend the books by Professor Volker Quaschning (well-known climate scientist in Germany), he goes into lots of stuff like this in detail.

For electricity, which is a small fraction of energy consumption overall. Most of the other sources are much harder to switch economically, and raise serious health and safety issues if storage and capacity is not increased dramatically.

For instance, for Germany to be self sufficient in the winter using electric heating, even if using high efficiency heat pumps, will require massive capex. Likely on the order of 7x all they’ve already spent on their entire electric grid.

I note you don't mention how much lower is the opex or when they'd start making money on that investment? A weirdly short term view.

It isn’t much better near as I can tell for most scenarios, but you’re welcome to provide some links to analysis if you’d like. I’ve posted a number of them in other threads.

A key attribute of those analysis is the interest rates for financing, which used to be near zero - and likely will not be for quite awhile, but good luck predicting that.

> and likely will not be for quite awhile, but good luck predicting that.

It will stay at 0% or go lower. Since when did Germany stop exporting? Since when did Germans stop saving? In fact, it gets easier to save with lower interest rates because it means people don't have to pay interest to the rich. 0% debt is much easier to pay off than debt that is growing exponentially at 10% per year.

I honestly think using interest rates as a throttle is a stupid idea. It would be more logical to introduce a minimum yearly payment to principal ratio and let the central banks control that instead, it would most likely be at 3% during normal times and 6% during inflationary times. Paying interest doesn't reduce the money supply only paying off the principal reduces the money supply and inflation. Raising interest rates is actually an ugly hack to create a recession which then reduces demand for loans. If people borrow anyway, like when a government borrows to service interest, it will actually feed itself and inflation will get worse than if the government lowered interest rates and just paid off the principal to reduce the money supply. When you look at Turkey they are forcibly lowering interest rates but not paying off their debt which is weird as hell, an increased minimum payment would be more effective at removing inflation.

If you take this further and introduce a debt brake or austerity, you will most likely get deflation which then means the interest rate must be negative to avoid a recession.

Well, there are fixed principal payments - it depends on the term on the loan, and is weighted in various ways when it gets paid, but generally it’s set when the contract gets written. Otherwise, how would the lender know how long the cash would be out of their hands?

Interest rates are supposed to cover the lender by compensating them more than they lose by writing the loan (due to things like the time value of the money, inflation losses, etc).

If no one pays interest worth writing the loan for (aka they get more money than they think they would lose at the end) then who is going to write it?

Maybe the gov’t as a policy thing? But ugh. Talk about a recipe for bad loans.

And if Germany writes themselves a bunch of Euro denominated loans for $20 trln worth of electrical equipment and infrastructure that would certainly bottleneck on a few, often foreign manufacturers? Then you’ll see that trade balance get weird quick.

What percentage of German GDP are we we actually talking about to get there?

What percentage of German GDP are we talking about saving every year after that?