Traditionally, moving energy around means batteries, and yes maybe your battery costs more than just generating new electricity from a less efficient new solar panel at odd hours. But batteries are optimized for energy being expensive, where losses are wasteful.
Consider this really simple, dirt cheap alternative: plug your free energy into a pool of water and collect the hydrogen from it. Burn the hydrogen later, and point the light at your idle solar panels. It's hellishly inefficient, but I repeat: the energy is free. You are only minimizing capital costs, at least until other people catch up and start shifting load some other way.
The sane point on this curve probably looks something along the lines of a mix of batteries and synthetic fuels powering existing fossil fuel plants. The nice thing about going all the way to synthetic fuels and not hydrogen is that long term storage becomes trivially cheap, so it starts offsetting your winter load as well.