1) it is orders of magnitude easier if we include nuclear, and
2) even with a nuclear baseline we will need to build up caches of supplemental longer term storage options such as synthetic fuels. The added resiliency is worth the reduced efficiency.
Nuclear also comes with a lot of geopolitical concerns, because it's not just "us good guys" who need a working power supply, but also "that rogue state, $insert_country_here". For example, Israel and the Begin Doctrine w.r.t. Syria, Iran, and Iraq.
We could also solve the same problem for reasonable $-cost with a really big HVDC line around the planet, with the same criticism: geopolitics is hard, yo.
For what time frame? That is, I can build an X Megawatt nuclear plant, and I can get X megawatts out of it hour after hour, day after day. But if I build LiIon, that's storage - a stock, not a flow. I can build X Megawatts for an hour, but if I need two hours, I have to double the storage.
Buy enough for e.g. a week of pure battery use, most of days you're using 1/14th of your total capacity, but that makes the system as a whole last almost 14 times longer between battery replacements than a system that only has the capacity to last overnight.
Sorry, I thought that was obvious, given that time factors out.
Two [minutes, hours, days, weeks, months], to a reasonable approximation doesn't change the price of electricity.
It's like asking in which fuel tank petrol costs more per litre, the big one or the little one.
You don't need to charge nuclear power plant, obviously.
For anyone else with an interest ..
South Australia ( small Australian state with some heavy industry ) has had prolonged periods of getting by on just battery backed renewable energy (wind, solar) with minimal baseload generation support - as part of a larger interstate grid they've exported excess energy to larger neighbouring states.
The Tesla built battery pack facility details are:
https://en.wikipedia.org/wiki/Hornsdale_Power_Reserve
https://hornsdalepowerreserve.com.au/
https://www.cefc.com.au/where-we-invest/case-studies/sa-big-...
and there should be enough actual real world details there to plug into any models people are making about wind + solar + battery at latitudes of 33° from the equator.
The installation cost of a battery storage system, spread over the lifetime of that system, is a bit less than the the cost of a nuclear plant spread over the lifetime of the nuclear plant.
Adding to that number the cost of a renewable power supply to charge that battery, spread over the lifetime of the power supply, makes it swings and roundabouts.
Way easier than recycling a few GWh of batteries every 20 years, or simply using a pumped hydro station.
Cost for renewable is $a/kWh, for batteries is $b/kWh for installation and $(b/c)/kWh for delivery where c is the effective number of cycles the battery lasts for.
a+(b/c) ~= the cost per kWh for nuclear, thought of course I'm painting in broad brushstrokes here and averages hide details.
You build a nuclear power plant, and it is capable of outputting X megawatts as a sustained output. The same plant that produced 100 (or however many) megawatts this now will also produce 100 megawatts next minute, or hour, or month. Same with solar or wind, except that it's not quite as consistent as nuclear. (On the other hand, you have to refuel nuclear plants from time to time.)
LiIon is different. It doesn't produce electricity, it stores it. You measure it in megwatt-hours, not in megawatts. The battery that you stored your first minute of standby power in is a physically separate battery from the one you store the next minute's standby power in. Two hours of standby power costs 60 times as much as two minutes, because you need 60 times as many batteries.
The only way your statement makes sense is if the cost of the batteries to store two months of power is only a rounding error compared to the cost of generating the electricity. That possibly might be true, but if you're claiming that, I'd like to see your source...
You could object to the amount needed up front, or use some reasoning based on discount rate, but you didn't.
Also it would be wrong even if you did because the energy needed for the infrequent long duration events is a small fraction of the total and doesn't need storing inna chemical battery. Even using gas for it for centuries would release less emissions than the emissions released whilst building the nuke instead of something reasonable.
If you use, say, 1 kilowatt constantly, then the minimum you need overnight is a 12 kWh battery, while a battery that lasts a week would be 168 kWh.
Let's say that particular battery lasts exactly 1095 complete cycles. The 12 kWh battery gets replaced every 3 years. The 168 kWh battery gets replaced every 42 years.
The cost per night is the same.