It's almost always cheaper to overbuild renewables than to use seasonal storage. Seasonal storage is used once a year, so if you can store a Kwh of energy for $1 it still increases the cost of the stored electricity by 4-5 cents per Kwh. Let's look at a 1 Kw average output. Assume that you have 6 Kw of solar, along with 18 Kwh of batteries. This will work fine 7-8 months out of the year, but will not be sufficient for winter, so you will need seasonal storage. About 2000 Kwh should be sufficient to make up for the deficit. Alternatively, how much solar would you need to avoid seasonal storage? About 10-12 Kw would probably work. That would mean an additional $3,200 to $4,800 in capital costs, assuming 80 cents per watt of solar. In order for seasonal storage to compete it would need to cost less than about $2 per KWh. For hydrogen this would equate to about $40 per kg. That's on the low end of estimates I've seen for underground hydrogen storage, and doesn't even take into account the cost of generating the hydrogen. It also doesn't take into account revenue generated from selling excess electricity in summer. Even if you sold excess electricity for only 1 cent per Kwh you could still offset about half the cost of the extra solar capacity.

I think many people see excess capacity as a form of waste to be reduced, but it's like thinking that gigabit fiber is a waste because it's not used to it's full capacity. The value of oversupply is that it's always available when you need it. The fact that new industries can spawn from the super cheap rates for excess electricity or data is just a bonus.