How to Heat a Swimming Pool with an Air Conditioner | Ask This Old House
Why Hacker News recommends it
HN cites it as a practical demonstration of reusing AC waste heat, in threads about heat recovery.
What it is
A This Old House segment where Richard Trethewey installs a heat exchanger that uses waste heat from a central air conditioner to heat a swimming pool.
Recommended by 0 HN commenters across 0 different months, 2019 to 2026.
What Hacker News said
Cites MichaelApproved · 2019-10 · on “24-Hour Solar Energy: Molten Salt Makes It Possible”
Houses with pools should use the waste heat from their air conditioning system to heat their pool. Unfortunately, the system requires an HVAV technician, an electrician, and a plumber to install. I’m also not sure how many HVAC techs are familiar with installing something like that. Seems like a great energy saver though. Here’sa video from This Old House on installing one of the systems. [this video]
Cites energ8 · 2020-04 · on “Heat Pump Water Heaters”
From my reading of heat pumps, mismatches in energy sources and sinks can make linking things together more complicated (aka more expensive) than is commonly available. For the pool <-> A/C case, This Old House did a segment on linking the systems: [this video] Edit: chris_va has more details about why linking systems is hard: [LINK]
Cites alexpotato · 2026-07 · on “Tiny data centre used to heat public swimming pool”
This does exist btw. It's a stainless steel coil that you can put on your A/C and then run water from your pool over it to heat the pool. [this video]