A few hours are sometimes enough to start generators when renewable energy supply decreases. Obviously, the more capacity the better, but costs will increase linearly with capacity in most cases.
Pumped-storage hydroelectricity - where it is feasible - is the only kind of energy storage close to "months".
Not just does the US no longer want to support Ukraine, it is basically siding with Russia by not taking a stand and criticising Ukraine. It’s neglecting the interests of it’s ally by only including Russia in negotiations.
On top of it all, it’s extorting Ukraine into giving up it’s minerals while giving no assurances in return.
And finally, most important for long term, it’s a complete policy reversal to its NATO allies, which will have a long term impact on US transatlantic relations for decades to come. Before, US was the only country to invoke Article 5. Now its recognising a weak moments for its allies and is exploiting that opportunity.
Pumped-storage hydroelectricity - where it is feasible - is the only kind of energy storage close to "months".