That's one consideration (and if storage gets as cheap as variable generation it will be the most important one). With the advent of cheap solar the value of mo

That's one consideration (and if storage gets as cheap as variable generation it will be the most important one). With the advent of cheap solar the value of moving the energy is a fair bit higher than its cost. So the economics become mostly a matter of cost of storage vs. duration. If you can move energy from a time where it's the least valuable generation of a system that costs $15/MWh net (or even less in future systems) to a time when the cheapest scalable generation is $50/MWh then you've got a lot of room for losing some. There's incentive for the solar system to overbuild 2x or 3x just to sell that 3pm-sunset energy so from their point of view they can sell the sunrise-3pm energy at any price over $0 and be profitable. A hypothetical bad second hand battery might be the most valuable (and thus highest bidding) use, but it will have to compete with other opportunistic loads.