There's some guy in South Dakota who sells a device that's wrapped around the sides of the kettle, near the bottom, to transfer in some of the heat from the flame wash that would otherwise dissipate upwards. Can't remember the name, but I recall seeing it advertised in Zymurgy a year or two ago.
IIRC, the device was rather expensive, like >$100, so it would take a lot of batches to recoup the savings in propane.
IIRC, the device was rather expensive, like >$100, so it would take a lot of batches to recoup the savings in propane.