You can't generate excess electricity because you don't have enough land or rooftop (I mean maybe you do, I'm talking about the typical homeowner). Utilities can overbuild panels because they're extremely cheap.
LFP batteries have a self-discharge rate of 2-5% per month. Once they're cheap enough, over-building batteries to move summer sunshine into the winter months also becomes an option*. At $100/kwh, you could power Sweden 6 months a year for about $60bn (EDIT: $6tn, sorry) in batteries (yes labor and everything else will probably double that cost). And that doesn't even account for recent advances in sodium batteries, which reportedly bring that price down to $20/kwh
* (Any battery experts know why this might be wrong? I'm using basic arithmetic, not physics. That tells me a battery charged to 100% in July or August will still have > 70% charge left in December)
In any case, at $100/kwh, it would cost $250bn (EDIT: $25tn sorry) in batteries and maybe the same in installation costs to power Germany for 6 months a year. At the lower $20/kwh price tag it would be more like $5tn, compared to Germany's ~$4.5tn GDP. Over 10 years it could be done.
(And 6 months' storage is maybe too much anyway)
This isn't to say they can't import it from elsewhere, they just can't make any of their own. Adding more capacity wouldn't do anything, it would take an incredible amount of batteries to handle the more extreme end of those "dark periods".
Seasonal or month-long periods of low-generation are another matter, and as-yet an unsolved problem. It may be that synthesizing fuels ends up being a sensible option here.
At least that's what I hear people saying.
Paying for the plant but not having to pay for it to run most of the time is probably cheaper than having it running most of the time.
Maybe there's opportunities for net metering for customers with backup generators. At the right price per kWH, I would run my generator and feed into the grid... personally, my fuel cost is likely too high for that to make sense very often, but I think there's likely some hidden capacity there with the right incentives.
Germany will require 100-150 GW capacity which cost about 1000 EUR/kW and would require an investment of 100+B EUR.
Electricity prices already skyrocketed in Germany and no end in sight.
Listen: I invested in PV, in low energy houses, in heat pumps - but the PV/wind strategy doesn’t work the way people would like them to in their ideology and Germany has proven that.
Now that you've built those plants, would you rather pay to operate them year round, or only when needed?
PV/wind won't help you reduce capex for winter, but it should reduce opex on gas. And that's something.
Spending capex on interconnections may reduce the total dispatchable capacity needed; if it's done carefully. Having more time zones in one grid helps because peaks correspond with time of day; having more latitude helps because day lengths and cloud cover varies. Having more of both helps because still air tends to be geographically bounded. But long distance transmission is expensive.
Germany has plenty of salt formations for very cheap hydrogen storage, and there are no geographical constraints on thermal storage.
Given that this all-nuclear world has electrolyzers, what then prevents these from being driven by renewables (perhaps buffered short term by batteries), and the hydrogen then stored (as has been done for decades in underground storage caverns, just like natural gas is stored)? And once that is done, what prevents some of that hydrogen from then being profitably used to drive turbines when electricity prices are high? Gas turbines burning hydrogen are nearly identical to ones burning natural gas (just minor differences in the combustors) and have been available industrially for decades.
Using reasonable projections for cost (some of which have already been superseded by lower figures), we can estimate the cost of providing synthetic baseload from wind/solar/storage in Europe, using historical weather data. It comes in cheaper than nuclear.