Thinking about ditching the gas heater, just run the heat pump alone

Had a customer up in Chagrin Falls, similar setup, pulled the gas heater thinking the heat pump plus a cover would carry him and he was fine right up until we got one of those arctic blasts where ambient sat in the 30s for four straight days, heat pump just couldn't keep up and the pool dropped like six degrees before it recovered. Myrtle Beach isn't seeing that kind of stretch probably but a cover only slows heat loss, it doesn't add BTUs, so on those genuine cold snap nights you're still fighting physics not just convenience. If it were me and I already own both I'd keep the gas as the January insurance policy even if it sits idle most of the year, cheaper than a customer call in the middle of a cold front wondering why the water's 68.

Dave's not wrong about physics but Myrtle Beach isn't Chagrin Falls, four days of 30s ambient just isn't happening down there, seen it a hundred times where guys keep gas "just in case" and it sits there rusting out the heat exchanger from disuse more than it ever saves them. If your cold snaps are more like a night or two dipping into the 40s, a good cover holds enough of that heat that you're looking at a slow drift not a crash, heat pump catches back up fine once ambient climbs back over 55 or so. I'd say run the numbers on how many nights a year you're actually under 50 there, if it's a handful I'd let the gas go and just accept the pool runs a couple degrees cooler those mornings instead of paying to maintain and insure a second heater for maybe five nights a year.

Tampa's point about the heat exchanger rusting from disuse is the one I'd underline, Frank, because that's not theoretical, gas heaters that sit idle for months build up condensation inside and the exchanger corrodes from the inside where you can't see it, so the "insurance policy" everyone keeps citing has its own expiration date whether you use it or not. Chemistry's not really my department here but that's just basic metallurgy, the same reason a car battery that never gets driven dies faster than one that does. If you're only talking a handful of nights under 50 in Myrtle Beach, I'd bet the maintenance and eventual replacement cost on a gas unit that barely fires eats into any savings from keeping it around. Not my area of gear expertise, I'm all liquid chlorine and a Dolphin for the cleaning side, but from a pure cost logic standpoint tampapoolguy's framing makes more sense to me than treating idle equipment as free insurance.

Alan's metallurgy point is real but I wouldn't lean on it too hard as the deciding factor, plenty of my customers have gas heaters that sit all summer and fire up fine come November, the corrosion thing happens over years of total neglect not one off season. What actually kills them faster down here is salt pools without a bond or zinc anode nearby, that's a different problem. So don't let Frank make this decision based on fear of the exchanger rotting, make it based on what Frank already said, a handful of nights under 50. That's the real number. If he pulls the gas and it turns out he gets more cold snaps than he thought, he can always add it back later, but a heat pump running steady with a decent cover is what I tell most people up and down the coast to just live with.

I got no heater at all so take this for what its worth, buddy, but the cover talk got me thinking, mine's just a cheap solar cover and even that thing buys me a good 4-5 degrees overnight on a normal Nashville night versus leaving it open. So I believe tampapoolguy on the "slow drift not a crash" thing, seen it firsthand just from that alone. Not the same as actual BTUs obviously but a decent cover is doing more work than people give it credit for, at least in my case.