When we hire a new employee, they often come with a lot of the same misconceptions about solar energy that our clients initially have. Our relatively new sales assistant, Christie, asked me this week about a topic that comes up quite frequently: Solar pool heating panels make the pool pump work harder.
It might seem logical, but it’s a myth!
Here are the reasons it comes up in our day to day consultations:
- Sketchy competitors say that another company’s solar panels cause more back pressure and this will somehow blow up their pump.
- Pool builders are afraid that solar panels will increase the pressure in the system, which they mistakenly believe will cause more energy use.
- Because we are lifting water to the roof, homeowners think the pump must work harder because it has more force against it.
To understand this issue better, we need to first define “work.” Work, the term in physics, refers to force times distance. When most people think of “more work,” they think of something that is harder, which must use more energy (electricity in this case). That’s true — if more work is done, more electricity is needed.
But the truth is that when a pool pump encounters a higher pressure against which it must push, the amount of water that is moved (distance in a given time) is reduced. In the case of a single speed pump, it only runs at a single RPM, and does essentially the same amount of “work” regardless of how much pressure exists in the system. The force increases, and the distance (or speed if talking about time) decreases. The “work” remains the same! For a given pump speed (measured in RPM), the amount of work it does, and energy use, will remain essentially the same.
From a practical standpoint, all that matters is whether your existing pool pump is capable of pumping water through the solar panels and back to the pool. Here are a few truths to debunk solar pool heating pump myths:
- Properly designed solar pool heating systems only add a few pounds per square inch of pressure to your pool plumbing. If the pool is designed correctly, and maintained and works properly, the reduction in flow will be negligible.
- There will be a small reduction in flow in your overall system, which means that your pump will need to run for a longer period of time to circulate the same amount of water. Again, since the reduction in flow is very little, it is generally not necessary to increase your pump run time (which would, in fact, increase “work” and pumping costs). Most people run their pumps too long anyway.
- Pool pumps that are “deadheaded,” meaning they have reached their maximum pressure rating or close to it, may be damaged. Again, in a properly designed and maintained system, this in a non-issue.
Solar pool heaters don’t blow up pumps, and they don’t make pumps work harder. The next time someone tells you a pool pump needs to work harder to overcome higher pressure, you will be better equipped to debunk the myth!
My solar panels are pumped thru my variable speed pool pump- does having the solar in crease my electric bill? I do not seem to notice any difference when it is on? My
new neighbor gave away
his panels as was told took too much electricity? Much cheaper than that electric heater I know- thanks for an answer and ha e a great
The answer is… it depends. If you have a variable speed pump with a proper solar controller you can run your pump at a low circulation speed and just increase the speed when your solar panels are on. This does increase the cost of operating your pool pump, but that is offset at least partially by the low setting for normal circulation. That’s the advantage of a solar controller – only run your pump at the necessary speed, balancing the effectiveness of your solar pool heater with the energy savings of the variable speed pump.
We see other solar contractors just running variable speed pumps at the speed necessary for solar, or worse, at a speed even higher than necessary. Pool service companies are largely clueless on how to actually save you money with a variable speed pump (at least around here in our experience). What you need is a knowledgeable solar contractor that actually cares about your electric bill to advise you on how to save money while providing effective heating performance.
I have a solar heating system. the system is programmed to run about 10h a day. And reach certain temp (85f). Both the Solar Heating and the Filter Pump are programmed t run together.
However, when the desired temp is reached, not only does the Solar Heater bypass is enabled, but the Filter Pump shuts down too.
What can be the cause of this behavior?
Are you saying that adding a solar pool heater will add zero increase in electrical consumption? Doesn’t lifting the water 15′ up to the roof add load to the pump motor?
Don’t forget – what goes up must come down!!! No, it would not add “load” to the pump in terms of electricity used. The pressure would increase, but that is due mainly to friction, not lifting the water to the roof. The siphon effect from water coming down negates the lifting. While beyond the scope of this article, technically the water moves slower and the pump is doing less “work” in a physics sense, so it would actually use less energy in theory. But that’s not the point. The concept is that adding a solar pool heater to a single speed centrifugal pool pump will not increase energy use.
Now that is not the case necessarily with a variable speed pump. When solar pool heaters are added to variable speed pumps, the pump speed needs to be adjusted to increase flow rate when solar is on and decrease it when it is off to balance energy savings with heating performance. Depending on how the system is set up, there may be additional pumping costs, but usually this is pretty inconsequential. The concept is rather than running a variable speed pump at the same speed all day, which is usually how pools are set up, we run the pump at a lower speed for normal filtration and a higher speed for solar heating, resulting in the same overall pool turnover and ending up with similar energy use.