First and foremost, THANK YOU, everyone, for replying to my post.
As you have discovered a heat pump in the dry Arizona winter cannot move enough heat into your pool to keep it swimmable . There's just not enough energy available in our atmosphere. It's great this time of year, my heat pump runs about an hour in the morning to keep the pool at 87F. But as winter approaches, I'll give up heating and set the temp to 58, just enough to keep the SWCG running. I guess a cover would help but I don't want the hassle of a cover. If I had nat gas available, I'd definitely switch or add. It will be MUCH more expensive depending on what you heat to in winter.
If you want on demand great heating you should switch to gas.
This is indeed the problem. Even when the air is warm, since there is very little humidity, the heat energy in the air is very little, and therefore the transfer is minimal as well. Combined with the evaporation and heat loss from the surface of the pool, it simply cannot keep up. It's basically 2 steps forward, 1 step back. I need something to be 3 forward, 1 back!
Your biggest problem is that the pool is uncovered. An uncovered swimming pool, in our dry climate with cool evenings now, can easily loose 6-8 deg F overnight. That is far more heat loss than an electric heat pump can handle. Also, as
@scottts stated, the air here in AZ is simply too dry for a heat pump to operate efficiently. While our air temps can exceed 100F, there is so little moisture in the air that it makes it harder for a heat pump to operate efficiently. Heat pumps need humidity because water vapor is what holds the "energy" (latent heat) in warm air.
If you have natural gas available and the run length from your meter to the equipment pad isn't too long, then a gas heater will definitely give you more bang for your buck as the energy cost per unit of measure for gas (Therms) works out less than the energy cost per unit of measure for electricity (Watts). On an equivalent energy basis, gas is cheaper.
But, to go back to my first sentence, all of this moot if you don't cover the pool. Without a cover, you will waste A LOT of money no matter what your heat source is...
You hit the nail on the head in regards to the dry air, cold night-time temps, and no humidity/low latent heat.
Unfortunately, the gas line would be long. From the meter to the equipment area is about 100 feet.
I do agree there is a definite benefit to covering the pool. I do have a solar cover, but I don't usually put it on until late October when the night-time temps start to get pretty chilly. Even with a cover, however, the heat pump cannot keep up during the late fall and winter months, even here in AZ. The temperature swings between night and day average about 30 degrees difference, and if it gets cold enough, the HP will shut down automatically to prevent freezing.
It works. So, what's the problem? What will gas do for you that the heat pump doesn't? Just let it run and keep it heated.
What is your cost for natural gas and for electricity?
A major factor of going gas vs. staying with the heat pump is the ability to heat whenever throughout the day/night and NOT worry about time-of-use/demand electric rates, which I have. So basically between the hours of 3pm and 8pm, I limit electric usage immensely. My pool pump goes into a very slow speed, basically just to keep the skimmer flow going, and my house's AC units shut down by way of pre-cooling and set-back thermostats. With that in mind, a heat pump makes perfect sense in a standard/fixed rate for electricity, but it quickly becomes a major hassle for TOU/Demand rates. Because of that, I can heat all night and all morning, but for the 5 hours after 3pm, I can lose much of the heat in the pool. Two steps forward, one step back.
Get a bubble solar cover if you don't already have one. Keep the heatpump until it needs repair and then swap it out for gas.
This is what I have been doing for the last few years. The heat pump just doesn't want to die!
from what I understand about the heat pumps is they are supposed to be run/on 24/7 and it heats when needed.. You are using it like a gas heater and only turning it on 3 or so hours.. I also agree with a solar cover when you are paying to heat the pool...
Interesting point, and I didn't think of it like that. Still could get me into BIG trouble due to TOU/Demand electric rates as previously mentioned.
