At the Riverside foundry, I heard the heat recovery only cuts about 10% of energy use, @murray.troy. I mean, that's okay, but it's not the huge change people are talking about. Maybe it's just me, but I've seen older systems that did almost as well.
Actually got closer to 20% at our place after some fine tuning. The older gear just can't hit those numbers. Key was matching the recovery rate to our actual melt shop schedule.