Laptops don't even use that much power. You guys are really not into home labbing or as good with tech as you think you are lol. Lots of people run older real servers and desktops as home servers. They use way more power than laptops. Raspberry Pis sound good but use progressively more power in each generation, and still struggle to compete with mini PCs and even older laptops in performance. They also never had good performance per watt. In performance per watt basically nothing beats a Mac Mini, though other mini PCs are also good. Laptops aren't bad in energy efficiency either. They are literally designed to run on battery so have as little idle draw as possible. They would be comparable to a mini PC if you turn off the display.
Edit: Modern RPis apparently use 25W, which is firmly in the territory of what a laptop would use when not running the screen or charging the battery.
RPis aren't energy efficient either. Any situation where you are thinking of putting more than one of them in a cluster you should just buy mini PCs instead.