the difference between Millivolt Pool Heaters and Electronic Pool Heaters?
Electronic Pool Heaters have a pilot that lights only when heat is called for. Similar to a modern kitchen gas stove, a small, electronic spark ignites the pilot when you turn the heater on. The pilot shuts itself off after the burners are lit.
Millivolt Heaters have a Standing Pilot. This means that a pilot burns all the time, like older gas kitchen stoves. Having a Standing Pilot (Millivolt Heaters) obviously wastes a small amount of gas. It can also attract bugs, rodents and snakes seeking out the warmth it produces.
Electronic heaters are micro-processor controlled. Circuit boards, similar to those found in modern computers are used to control and analyze the heater functions. This also allows for LED indicators for temperature and troubleshooting. Electronic pool heaters also have the advantage of easy integrations with modern pool controller systems.
Which is Better?
Ten to Twenty years ago, I would have said Millivolt. Early electronic models had their fair share of irritating problems, coupled with my mental block on working on them. I would profess to love "Mechanical Devices, not Electronic Devices." But now that my understanding of Electronic Heaters has grown, I would say that they are simpler to install, and easier to troubleshoot than Millivolt Heaters. For Me!
If you plan to work on this heater yourself, and you understand Millivolt Heaters, and share my earlier mental block on electronic circuitry, then your choice is simple. If you plan to have pool service companies work on it, then I would recommend electronic. In another few years, the knowledge base will switch, and pool techs will be scratching their heads trying to figure out how to work on these old school "confusing" Millivolt heaters.