A rational economic miner will power down when the revenue drops below the cost of the electricity, and will decommission and/or sell the equipment when there's little expectation that a rig will be profitable again at a level sufficient to warrant not converting that equipment into bitcoin through a sale.

But not all miners are acting rationally in economic terms. Perhaps they are mining to obtain KYC-Free coins and are willing to pay 20% more than spot (in the cost of electricity) for their coins. Some miners simply aren't closely monitoring the price.

But there definitely is capacity that is offline today that would come back if (when) the price rises at a rate faster than the difficulty.

There also is hashing capacity taken offline due to curtailment measures, e.g., during hot days in Texas when the grid will buy that electricity at a premium, or there's drought seasonally (or not) affecting hydropower like what miners in China would undergo annually, or also relocation of equipment like what Compass is currently doing after the hosting facility in Georgia they used shut down. But that is not going to be that much of a fraction of the hashrate as the Texas example is only during parts of a day for a limited number of days, and both the drought in China example and Compass facility closure were temporary only as the equipment was too valuable to be left idle -- it was offline only until removal of the equipment at one site, transport and then re-installation at a different site were completed.

Now if (when) bitcoin mining ASIC hardware becomes commoditized, such that CapEx / depreciation is only a tiny fraction of the equation, then yes -- there could be more solar powered miners running just six to eight hours per day, miners that routinely power down when the wind isn't blowing, or ops that run from the grid when baseload power (e.g., from hydropower, nuclear) exceeds demand and a hefty price discount is available. That could bring the condition where there's a significant amount of hashing capacity that is offline at any one point in time. But for the time being those will be isolated instances. Maybe a decade out, if I had to take a guess, that might occur. But even then, those mining 24/7 on stranded energy will have the advantage.

The key is to watch the cost for hardware that should be obsolete at this point. About 30 months ago the Antminer S9 was being decommissioned and sold off for scrap -- under $50 apiece. Then after bitcoin rallied and issues erupted and persisted with ASIC mining manufacturing + supply chain, the cost for a used S9 rose to over $600. Today they are in the $150 to $200. In other words, miners that have done the math and decide to sell those are finding buyers and most of those buyers are plugging them back in. And S9s are nowadays just a small fraction of the hashrate. An almost nobody is powering down S19s they paid $6K to $10K for to then just watch and wait for better days.