Time for two solar panel to heat 40 gal tank

[leilanidude]

Doesn't your water heater have auxiliary electric or propane as a backup? If so, is it not turned on?

My water heater tank is 120 gallons. It lasts about 3-4 days without sun and I simply flip on the breaker for the aux electric element if I need more hot water. Also, my panels get the water in the tank to about 135 degrees. I simply have the "blend" set to keep the temp going out to about 105 to prevent scalding at the faucets.

[MarkP]

What type of solar panels? Photo-voltaic or solar thermal? How big?

[eigoya]

Thanks. The flipped backup switch was the issue, so not so much about recovery time. All good points to consider, though. Thanks again, Punaweb.

[kalianna]

I think the most difficult part might be finding some sun to charge it. :-)

[Space Karen]

If you don't mind additional plumbing.

There is something called a solar water heater that works better for this than solar panels.