How to Install a Solar Panel to an Existing Hot Water Tank

The bad news is that unless your hot water tank is designed to integrate with a solar panel then it can’t be done.

Traditional hot water tanks are designed to be heated by a boiler, and/or they are fitted with an electric coil. This hot water is generally used for showering or washing not heating the home.

A hot water tank which has been produced for use with a solar panel is designed to be heated by a boiler and/or an electric coil and a solar panel. The way the hot water system works is that it has a copper coiled pipe inside the top of the tank which is connected to your boiler and has a second coil at the bottom which is connected to your solar panel.

The tank is filled with cold water from your mains supply or a header tank. The fluid that is heated by the solar panel is pumped to your hot water tank, it travels around the coil in the bottom of the tank and while doing so, transfers heat from the fluid to the cold water in the tank via the copper pipe. This cooled fluid is then pumped back to the solar panel where it is heated again and this continues until the cold water in your tank reaches the desired temperature.

If the cold water in the tank does not reach the desired temperature from the fluid heated by the solar thermal panel (because the suns energy is not strong enough) then the systems control panel instructs the boiler to kick-in, which then circulates hot water to the top coil in the tank until the required temperature is met. This ensures you have hot water all year round.

Therefore, unless you have a tank with a coil at the top and one at the bottom then you can’t fit a solar panel to it.

Unless, I hear you say, what if you pump the cold water from your tank to the solar panel and keep circulating it until it heats up? Well, you still have a couple of problems.

The first one is retrofitting a flow and return (inlet and outlet) connector to your hot water tank. Hot water tanks are either made of thin copper or thin stainless steel. They are sealed units so you do not have access to the inside, so there is no way you can fit these connectors.

Even if you could, you are still faced with another problem and that is stopping the water in the solar panel from freezing during the winter months because you can’t antifreeze in the water like you can with a closed loop system.

You could use evacuated tube solar collector panels in contrast to flat plate solar collectors because they won’t freeze. However, if you are going to use evacuated tubes, then you may as well go a step further and invest in a new hot water tank.

If anybody has any suggestions on how you can install a solar panel to an existing hot water tank or would like to add something to this article then please leave comment below.


One Comment on How to Install a Solar Panel to an Existing Hot Water Tank

  1. Chris Kear on Sat, 14th Apr 2012 6:50 am
  2. You’re wrong. Several companies including Apricus, provide special 3 way valves which enable the hot water from the evacuated tube system, to be fed to the middle of a conventional hot tank, by passing a 12mm copper pipe through the cold water inlet at the bottom of the tank. This does not disrupt the cold water supply to the tank, because concentric copper pipes are used, the outer feeds the cold water to the bottom of the tank and the inner feeds hot to the middle of the tank. This system is very efficient.

    So, I think you ought to eat your words and go take a look.

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