Green Energy

I imagine it'll shift the mentally on electric heating (mainly through heat pumps) first. People have been outright hostile towards it, but once energy's free or negatively priced at peak, people will want to make the switch. People who own a large reservoir and a decently sized battery might be able to not pay for any heating or electricity in a good month.

As for industry, those that can allow for flexible production schedules will and in parts already have adapted to fluctuating energy prices. Whether that means less production in winter, or just adjust workflow so peak demand is during peak supply