On Dec 16, 10:50*am, infiniteMPG wrote:
I have an active direct circulating solar hot water system in my
Florida home for family use (not for a pool or anything like that) and
had it installed around 20 years ago. *It consists of an 80 gallon
tank and a roof mounted panel, I also added a Little Gray Box timer so
in case there's not enough sunlight it will heat the water
conventionally at times of high use (morning showers, etc). *In the
last couple weeks my youngest moved out to his own apartment so it's
just me in the house. *My tank is nearing it's life expectancy so it's
time to replace. *My question is should I stick with the 80 gallon
tank or go with a smaller tank, like a 50 gallon? *I can see if I
don't have enough sun to heat the water, the electric means to heat 80
gallons is pretty taxing. *But I can also see that on sunny days
(which we have a lot of), you'd want to capture as much of that heat
as possible. *Don't want to get into an 'overheating' condition since
it's direct circulating the water in the panel has to be kept under
the boiling point and the only way to do that is to circulate cooler
water thru, and with a 50 gallon tank it might mean it has to vent
steam pressure to prevent panel damage.

With the difference between the 50 gallon 12 year tank and the 80
gallon 9 year around $150, and around $200 difference between the 50
gallon 12 year and the 80 gallon lifetime, my question is should I
stick with the 80 gallon? *Also don't want to be paying to heat 80
gallons of water electrically on cloudy days.

Any suggestions?

You need pro advise , maybe alt.energy.homepower I would be thinking
to not heat the tank but use it for solar storage, if its near hot
enough a cheap small electric 20-30a tankless would be far more
efficent, for single use it probably would be all you need. but what
about a cloudy week or month.