I'm not actively working on this tech, but I've read just a little bit and it sounds like it's very cost-effective.
Check out what Princeton University is implementing on their campus.
Ted Borer - Energy Plant Directory at Princeton University. See video at 1:25.
Thanks for the shout out @Eric-Vanular. My research into UPHS has now led to a company called Terrament. In the near term we're actually focusing on solid-mass underground gravity storage instead of UPHS -- just because it's easier to start with. Here's our latest semi-public slide deck if anyone wants to check it out.