This seems an unpopular opinion, but maybe we don't need more base load. Maybe we need more on availability load. With all the magic of connected devices, they could cope with varying electricity?
Of US Commercial electricity use about 40% is refrigeration, cooling, heating, and ventilation which can all time shifted at least intra-day with good building practices.
10% is lighting which realistically can't - you need lights when it's dark.
15% is computers which can sort of load shift because most office computers are now laptops - with good communications systems you can tell laptops how aggressively to charge / whether to run off battery.
The rest is "other" quite a lot of which is small electronic devices like tablets and phones charging and then a grab-bag of misc. stuff.
Half of residential electricity is some kind of temperature shifting (heating, cooling, refrigeration, freezers, ventilation).
Essentially with good insulation you can get to a point where you can load shift 50%+ of your electricity consumption on an intra-day basis.
Electric car charging of course is a perfect load to match to renewables as well.
That doesn't solve the issue of inter-day fluctuations - what happens when you have a cloudy, high pressure system sitting over a substantial part of your generation for a week - but it does mean that we can go pretty far. We may have to keep more open-cycle gas around for those times which will have to be funded on a capacity basis.
"with good building practices", "get to a point" this is planning an ideal future despite having a system where the legacy infrastructure very much still needs to be accommodated for. We can't disregard what already exists, and that involves a considerable amount of base load.
1) We don't yet have enough renewables for this to be an issue. Even with the most optimistic possible build-out timelines for additional renewable generation, we will not do so for another decade or two. That's why it's important to change building practices for new-build and refurbs now since the incremental cost for additional insulation is much less than the cost of retro-fitting.
2) "base load" isn't the best term here. Base load refers to the load that makes up the bottom of the load curve, basically a straight horizontal line right under the trough in demand. Some of base load actually is flexible load - for instance refrigeration equipment that runs overnight can be timeshifted by an hour easily (although in that case it is rarely done because power prices are cheap at that time). The problem for renewables is not base load but non-flexible / non-dispatchable load that must go on when requested such as lights or televisions.
