How many degrees warmer do solar heaters get the water?

[J.P.M.]

I understand. Without busting on you, your customer or anyone, the situation you describe may be at least partially the result of the type of either/or dichotomous thinking that is often resorted to - either solar or fossil, not both. Some other thinking, such as can the fuel savings alone justify investing in a solar water heater in addition to a gas fired heater ?

[LucMan]

The gas heater is per hour, the solar thermal per sunny day. I wasn't trying to Say that the capacity was the same.
I service a residential 125k btu pool water HX and boiler, it runs for approximately 6 hrs per day to maintain 80 degrees. They use a cover when not in use. I tried to sell them a thermal system but the $ vs savings does not work out because of the year round use and low sun hrs in winter.

The solar energy is free. The best way to heat a pool from an economic standpoint probably includes solar energy collection equipment that is usually not free.not free.

A properly designed solar pool heating system can produce as much heat as needed over the course of a season or year round if that's the duty.

The point of design is to find the best way to meet the required duty - in this case a pool water temp. that is suitable.

Usually that's some combination of pool cover/solar collection equipment/backup heat source (that is usually fossil fuel fired) that best meets the user defined needs in the best combination (after safety) of tradeoffs between, most practical, least maintenance and most cost effective, again as defined by the owner/user.

To say that 5-6 panels may match the output of a 120MBTU gas fired heater is too loose a statement to put a lot of faith in.

Depending on location, time of year, etc. a common, decent solar pool heater might add 600-800 BTU/ft^2 of collector area to a pool on a warm, sunny, summer day. Less when the sun is lower in the sky, or a pt. cloudy day when it's cooler. The collector area is one of the design outputs.

Usually, a 1st cut is to have the collector area about half to 2/3 the size of the pool surface area, but that's not a substitute for a decent design attempt including all opportunities for heat retention/addition.

[J.P.M.]

A gas pool heater can be rated at 120k btu per hour.
5-6 Solar panels could produce that much in a day of sunshine. But it's free energy!

The solar energy is free. The best way to heat a pool from an economic standpoint probably includes solar energy collection equipment that is usually not free.not free.

A properly designed solar pool heating system can produce as much heat as needed over the course of a season or year round if that's the duty.

The point of design is to find the best way to meet the required duty - in this case a pool water temp. that is suitable.

Usually that's some combination of pool cover/solar collection equipment/backup heat source (that is usually fossil fuel fired) that best meets the user defined needs in the best combination (after safety) of tradeoffs between, most practical, least maintenance and most cost effective, again as defined by the owner/user.

To say that 5-6 panels may match the output of a 120MBTU gas fired heater is too loose a statement to put a lot of faith in.

Depending on location, time of year, etc. a common, decent solar pool heater might add 600-800 BTU/ft^2 of collector area to a pool on a warm, sunny, summer day. Less when the sun is lower in the sky, or a pt. cloudy day when it's cooler. The collector area is one of the design outputs.

Usually, a 1st cut is to have the collector area about half to 2/3 the size of the pool surface area, but that's not a substitute for a decent design attempt including all opportunities for heat retention/addition.

[LucMan]

A gas pool heater can be rated at 120k btu per hour.
5-6 Solar panels could produce that much in a day of sunshine. But it's free energy!

[J.P.M.]

And over time those degrees add up.
Although the output water from the solar heater is only a few degrees warmer than the input, you can still get a significant temp difference compared to an unheated pool.
I pretty much only run the pool furnace when I want to heat up the hot tub (the hot tub and pool share equipment - the hot tub overflows into the pool.)
I'm removing panels though - going from 10 to 6 to make room for PV panels. So we'll see how I do this summer.

Of course they do. that's how they are supposed to operate.

[foo1bar]

For reasonably well designed systems:

Pool heaters usually operate a few degrees above the pool water temp.

And over time those degrees add up.
Although the output water from the solar heater is only a few degrees warmer than the input, you can still get a significant temp difference compared to an unheated pool.
I pretty much only run the pool furnace when I want to heat up the hot tub (the hot tub and pool share equipment - the hot tub overflows into the pool.)
I'm removing panels though - going from 10 to 6 to make room for PV panels. So we'll see how I do this summer.

[J.P.M.]

How many degrees warmer do solar heaters get the water?

For reasonably well designed systems:

Pool heaters usually operate a few degrees above the pool water temp.

Well designed solar domestic water heaters will usually, on a sunny day, depending on a lot of variables, heat a tank of H2O something like 40 to 80 deg. F. per day above the cold water temp. Lots of variables make that a VERY approx. #.

[inetdog]

How many degrees warmer do solar heaters get the water?

It depends on the panel type and the flow rate.
An evacuated tube collector could raise 80F degree water to 250F water pretty easily at a flow rate near zero, while a flat panel collector would be working pretty hard to get to 180F.
Because of the details of heat loss from the panel, the maximum temperature increase will not necessarily be independent of either the input water temperature or the ambient air temperature.

A pool heater with a high flow rate might only increase the water temperature by a few degrees, but the effect would add up as the pool temperature (inlet water to the panel) increased.

[MikeInRialto]

How many degrees warmer do solar heaters get the water?