Docs911 said:
The dealer who sold me the pool and set it up highly suggests the heat pump. He is telling me that the solar panels won't get me much more than 10 degrees. If I want temps in mid 80's , he is telling me that heat pump is the way to go.
That is simply not true if you are looking at a reasonable number of solar panels and you also use a solar cover. In my pool between a relatively thin opaque pool cover and solar panels (about 78% of the pool surface area since 2 panels are mostly in shade) I easily get over 20ºF higher pool water temperature than average day/night temperature. If I had a more insulating bubble-type cover, this would be more than 25ºF higher. A cover alone gets around 10-15ºF depending on the cover (clear ones allow some sunlight through). For the most heating, you would get a more clear bubble-type cover so that sun can heat the pool directly as well.
The sun's energy output (insolation) in
Virginia is around 80% of where I live near San Francisco so instead of getting over 25ºF higher than average day/night temps with a bubble-type solar cover plus solar panels combo, you might get over 20ºF average day/night temperature. I'm not sure where you live in Virginia, but using the temps in
Richmond, VA I get the following for avg. day/night (rounded up) temperature, the insolation (for panels tilted at 15 degrees less than latitude so tilted 22.5º towards south), and expected pool temp:
MONTH: ......... Jan .. Feb .. Mar .. Apr .. May .. Jun .. Jul .. Aug .. Sep .. Oct .. Nov .. Dec
INSOLATION: .. 3.2 .. 3.9 .. 4.8 ... 5.5 .. 5.8 ... 6.1 .. 5.9 .. 5.7 .. 5.1 ... 4.4 ... 3.5 .. 2.9
AVG. TEMP: .... 37 .... 40 ... 48 ... 58 .... 66 ... 74 ... 78 ... 77 .... 71 .... 59 ... 50 .... 41
POOL TEMP: ... 48 .... 53 ... 64 ... 76 .... 85 ... 94 ... 98 ... 96 .... 88 .... 74 ... 62 .... 51
In practice, you wouldn't bother using the solar in the off months since it just uses more pump electricity and you won't be using the pool. You also wouldn't heat it as hot as I indicate in June through August -- a solar cover alone would be sufficient for those months (especially July and August). The solar panels really are there to extend the season into May and September (maybe late April and early October if you swim in lower 80's). My numbers might be too conservative if you use a good mostly clear bubble-type cover (i.e. you can get more heat retention in that case as well as some direct solar heating) but for solar panel heating I assume a fairly large panel area of around 80% of the pool's surface area.
If you do not use a solar blanket, then you won't be able to get the pool warm enough when it gets really cold at night in late April and early October and even May will be difficult. With no solar blanket and no solar panels or other heat source other than the pool hitting the pool your pool temperature will probably get to no more than 5ºF warmer than the average day/night temp shown so in the low 80's in July and August, but that's about it (this assumes a white plaster pool; with a dark vinyl or painted pool it could get perhaps 7-8ºF warmer if there isn't wind). You can get your pool warmer in those months (if you wanted to) with either a solar cover or solar panels but both together are certainly not needed in those months nor in June.
