I'm a new owner (July 2022) and learning the pool maintenance ropes on my own. I like to swim laps in my pool for 20-25 minutes daily. I plan to use my first year to figure stuff out. My current goals (perhaps misguided) are to figure out the most cost- and time-efficient method of maintaining the pool chemicals and water temp so I can swim year-round. So far, pool maintenance has been way more work than I expected.
Right now, as winter approaches, my focus is largely on water temp (also some algae issues). I suspect keeping temp warm enough for lap swimming will require some combination of a pool cover, solar panels, and wetsuits. I figure I need to keep the water above 65F and maybe above 70F during winter. I don't want to use gas to heat the pool.
We have a great climate here in Riverside in terms of solar energy. I bought a pool cover a month ago, and that has been effective so far (I know -- winter hasn't started). Today the water temperature is 76F after 2+ rainy days where the air temps never reach 70F and were down to 62 at night. The average temp over the past 48 hours was about 66F. This suggests the pool cover is helping a lot (5-7 degrees even when there is no sun).
I just made some measurements and calculations to estimate the degree to which solar will heat the pool in winter. Right now it is in the sun most of the day and the water temp is perfect. The sun angle at high noon (12:36 pm, currently), is 49 degrees. My home is about 7 feet directly south of the pool. The roof of my home is about 8'1.8" or 8.15 feet tall. To calculate the degree the home will shade the pool (the home's shadow), I took the reciprocal of the tangent of the sun angle ((1/(tan of 49)= 0.869). The shadow is the product of that value and the roof height (8.15*.852=7.08 feet or 7'1"). I measured the shadow with a tape measure, and the estimate is very close.
Moving ahead to the winter solstice (Dec. 20th this year), the sun angle will be about 33 degrees. Using the same method, the shadow should be about 12.6 feet. If so, it will cover about 45% of the pool's surface. Also note that compared with Oct. 9th (now), fewer direct rays (49 vs 33), 1:40 shorter days (11:33 vs 9:53), much colder average temperatures (70 est now vs 54 est. Dec), and much more cloudy daytime skies (83% for Oct. 9 vs 60% for Dec. 20), the pool cover will provide far less solar benefits in Dec. I will see how much thermal benefit it provides, but much of that will be nighttime insulations and 24-hr evaporation reduction (less cold entering at night from the air, less heat loss during the day due to evaporation). If it heats the water 5 degrees, I will be satisfied. That brings the temp to about 60 degrees, which is too cold to swim even with a wetsuit.
I expect the water temp to be too cold (below 77) to swim without a wetsuit from Nov. 1st when the sun angle is 41 degrees, the shadow is 9.4 ft (90% of the pool is still in the sun), the day length is 10:45, and the average temperature is projected to be 64, and average cloud cover at 70%.
By Dec. 1st the water may be fridged, as the days will be 10:02 hrs, the sun angle 34 degrees, the shadow 12.1 ft (40+% of pool in shade), and the average temp. 57 degree. The water temp may only be 62.
This winter will be for data collection and experimentation. I will then use the new information to figure out the easiest and least expensive way to keep the pool temp swimmable year-round or decide it is too much trouble. Unless I take 4+ months off of swimming, I will need an external heat source such as some combination of solar and a heat pump to keep the water at least 72 degrees, swimmable with a wetsuit.
Right now, as winter approaches, my focus is largely on water temp (also some algae issues). I suspect keeping temp warm enough for lap swimming will require some combination of a pool cover, solar panels, and wetsuits. I figure I need to keep the water above 65F and maybe above 70F during winter. I don't want to use gas to heat the pool.
We have a great climate here in Riverside in terms of solar energy. I bought a pool cover a month ago, and that has been effective so far (I know -- winter hasn't started). Today the water temperature is 76F after 2+ rainy days where the air temps never reach 70F and were down to 62 at night. The average temp over the past 48 hours was about 66F. This suggests the pool cover is helping a lot (5-7 degrees even when there is no sun).
I just made some measurements and calculations to estimate the degree to which solar will heat the pool in winter. Right now it is in the sun most of the day and the water temp is perfect. The sun angle at high noon (12:36 pm, currently), is 49 degrees. My home is about 7 feet directly south of the pool. The roof of my home is about 8'1.8" or 8.15 feet tall. To calculate the degree the home will shade the pool (the home's shadow), I took the reciprocal of the tangent of the sun angle ((1/(tan of 49)= 0.869). The shadow is the product of that value and the roof height (8.15*.852=7.08 feet or 7'1"). I measured the shadow with a tape measure, and the estimate is very close.
Moving ahead to the winter solstice (Dec. 20th this year), the sun angle will be about 33 degrees. Using the same method, the shadow should be about 12.6 feet. If so, it will cover about 45% of the pool's surface. Also note that compared with Oct. 9th (now), fewer direct rays (49 vs 33), 1:40 shorter days (11:33 vs 9:53), much colder average temperatures (70 est now vs 54 est. Dec), and much more cloudy daytime skies (83% for Oct. 9 vs 60% for Dec. 20), the pool cover will provide far less solar benefits in Dec. I will see how much thermal benefit it provides, but much of that will be nighttime insulations and 24-hr evaporation reduction (less cold entering at night from the air, less heat loss during the day due to evaporation). If it heats the water 5 degrees, I will be satisfied. That brings the temp to about 60 degrees, which is too cold to swim even with a wetsuit.
I expect the water temp to be too cold (below 77) to swim without a wetsuit from Nov. 1st when the sun angle is 41 degrees, the shadow is 9.4 ft (90% of the pool is still in the sun), the day length is 10:45, and the average temperature is projected to be 64, and average cloud cover at 70%.
By Dec. 1st the water may be fridged, as the days will be 10:02 hrs, the sun angle 34 degrees, the shadow 12.1 ft (40+% of pool in shade), and the average temp. 57 degree. The water temp may only be 62.
This winter will be for data collection and experimentation. I will then use the new information to figure out the easiest and least expensive way to keep the pool temp swimmable year-round or decide it is too much trouble. Unless I take 4+ months off of swimming, I will need an external heat source such as some combination of solar and a heat pump to keep the water at least 72 degrees, swimmable with a wetsuit.
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We have a few experts who can collaborate with you regarding solar issues. You can start a new thread just for that subject if needed later. Enjoy the forum. 
