Close this search box.

DIY Solar Water Heater: An Ultimate Guide

However, the solar hot water systems in the past were often failure-prone, ineffective, and leaky, but thankfully, the industry has grown and matured. 
Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Today consumers have a choice between super-efficient, professionally installed collectors and also the less expensive DIY friendly solar water heater system.

The bonus is that you don’t need to sacrifice the convenience of a regular hot water system when you install a solar heating system. They are simply designed to tie into conventional electric or gas water heaters. 

Therefore, you can enjoy the convenience, the benefits, and the savings of both options. In the following guide, we’re going to take a look at DIY solar water heater (see also ‘Water Heater Disposal‘) options and why you should be considering them.

How does a solar water heater work?

How does a solar water heater work?

A solar water heater works by absorbing light. Ultimately, the light is absorbed by means of a collector placed on the roof and ultimately converts the sunlight into heat.

This heat is then transferred to the water tank by means of a circulating pump. Then the exchange is triggered by the regulator but only when the collector is hotter than the water in the tank. 

This prevents the circulating pump from using electricity unnecessarily. It also prevents overheating. At midday, in summer, when skies are cloudless is when the efficiency of the collective is at its highest.

Alternatively, they also do well when the collectors face south. When there is not enough sunlight, the water is preheated, and a backup system kicks in to bring the water to the required temperature. 

The system ultimately is used to produce hot water at a constant temperature throughout the year without emitting any CO2. You’ll find that solar water heaters are usually described according to the type of connector and the circulating system that they use.

Do solar water heaters work in winter or fall?

Many people who haven’t used solar water heater systems before often wonder whether they can be used at night, during the winter and the fall.

As with all things in life, there are advantages and disadvantages. Let’s take a closer look at how your solar water heating system works during the winter and fall.

Even with outside temperatures being low in winter, it shouldn’t affect your solar water heater. This is because, with good insulation, the sun will still be able to heat the water even during the winter months.

This is because the hot water tank is heated up by the radiation energy of the sun which goes through the glass and heats up enclosures even if the outside temperature is well below freezing. 

Therefore providing good insulation can ensure only a small amount of heat loss.

Diffused sunlight, however, which is often a feature on cloudy days reduces the heating capacity of most solar water heaters. So there is no specific technology to suck out more heat from the sun’s rays to the collector. 

However, you can enhance the amount of light hitting the right area using mirrors such as concave ones so that the few hours of direct sunlight available can be optimized.

Ultimately though, the quality of the insulation and how much heat can be kept in the system without being lost in the environment are all factors that play a role in how your solar water heater will work during these cold months.

The reality is that solar water heaters don’t generate as much hot water in winter. However, solar water heating systems that are installed in winter will have anti-freeze protection, and the snow will then melt off your solar water heating collector before it slides off your roof.

The solar water heating system can be effective because of the sufficient insulation. 

So ultimately, as we mentioned earlier, the radiator fluid technology will kick in during colder days.

The system makes use of a liquid catalyst radiator which is warmed by the sun’s energy and then pumped into the heat exchange tank. The heat exchange tank exchanges the heat of the fluid with the water in the storage tank. 

The radiator fluid should be checked prior to the winter months. Consequently, the vacuum tubes produced by some small manufacturers may be of poor quality and lead to low-thermal efficiency of hot water production. 

On the other hand, if the anti-freeze installation is weak, then it weakens the insulation effect, making it ineffective. It will consequently struggle to keep your hot water warm. Also, if the pipeline is frozen, the hot water circulation will not be smooth or only partially heated.

Ultimately, by ensuring that you have good insulation, sunlight will be able to heat the water well in a solar water heater system.

When it comes to temperatures below freezing, you need to remember that solar water heaters are not developed or designed to replace your water heater altogether. A typical solar water heater will be able to heat 60 to 80% of the water you use over the course of the year. 

So from April to September, almost all of the hot water will be solar heated. In winter, however, the percentage of your hot water will be more like 10 to 20% due to the shorter days and because of the weaker sun in December. 

Therefore, 99% of solar water heaters installed in the US are connected to a backup conventional water heater, and your water needs continue to be met even in colder months like January.

What do you need to make your own DIY Solar Water Heater

In order to make your own solar water heater, here are the tools that you need: 

Drill and drill bits

An adjustable drill machine works best. Opt for one that’s suitable for wood, plastic and metal.

Forstner drill bits

This piece of equipment is used for making holes in metal and plastic. It can also be used to drill holes in the storage tanks, as well as drill holes for input and output pipes etc.

Screwdriver set

You need a screwdriver set with a variety of different types of screwdrivers, for example, slow, torx, cross etc. The screwdriver is fast and easier to use with an electric drill.

Right angle clamps

This is optional; however, they are very useful in helping to make easy 90° angles without the need for holding it all together with your hands.


When it comes to choosing a saw, a simple one that works with wood and metal will do, alternatively to make things easier you can opt for a circular electric saw when cutting metal and or to put in the desired angle.

Metal sheets scissors

This is for cutting sheet metal like aluminium.

Copper tubing cutter 

This is used for cutting copper tubes. When using a tubing cutter,  hold the copper tubing and clamp the cutter around the pipe you want to cut.

Thereafter, spin the cutter around the pipe tightening the knob slightly on each turn to increase the cutting wheel pressure on the pipe. You may find some burrs in the pipes cut edge after making the cut, and in order to remove this, you need to use a small file or burring tool.


Paint brushes will be used to add paint to the copper pipes, inner walls of the collector as well as the absorber plate. Be prepared for the step because you may need more layers before the whole absorber is covered. 

Burner and soldering equipment

This is used for soldering the copper tubes together. It includes a burner and soldering equipment including his soldering paste flux.

Silicone gun 

This will be used to seal off the solar collector. It’s applied between the metal profile, wood as well as the solar glass etc.

PP–R pipe welding equipment

This stands for polypropylene random copolymer, which are the most reliable in plumbing and water supply plants. They are also used by the health organization due to the chemical features and fusion welding. Heat is necessary to cause the pipes to melt.

Copper pipe bending tool

The copper pipe bending tool is used if the copper tubing in the solar collectors is made with a single copper pipe. The copper pipe (see also ‘ How To Connect PVC To Copper Pipe’ ) is then bent in a meander shape.


When working with PP-R pipes, you need special scissors that are used to cut the pipes.

Standard tools

The set of tools in your standard tool arsenal will be needed, including hammers both metal and plastic, measuring equipment, meters, a scalpel, a wrench as well as different types of clamps etc. 

Safety equipment

This is used in all phases, especially while cutting metal with a circular saw and working with drills and banners etc.

The materials you’ll need to build a solar water heater include: 

  • Treated wooden planks
  • Transparent cover glass
  • Aluminium sheet
  • Aluminium L profile
  • Aluminium foil
  • Copper tubes
  • Insulating material
  • Barrels for hot water storage
  • Matt glass paint
  • Silicone
  • Screws for wood and metal
  • Check valve
  • Various types of adapters, rubber seals and valves
  • Thread seal paper
  • PP-R pipes
  • Tape and plastic wrap

Steps to make your Solar Water Heater

Step 1

The first step to building a solar water heater is to design and build a wooden frame for the solar tank. One side of the box should be inclined so that the glazing can have better sun exposure.

Step 2

In this step, you need to build the walls or sides of the heater box using plywood. The inside of the box should be covered with materials like Styrofoam, aluminium or fiberglass insulation.

Step 3

Here, you’ll need to figure out where the plumbing will be installed before you build the heater box. You also need to know where the designated opening for incoming water and exiting pipes will be located.

Also bear in mind how it will be connected to the heating system and house plumbing.

Step 4

In order to make your DIY solar heater more efficient, you need to insulate the pipes to reduce heat and energy loss.

Step 5

The final step is to cover the box. There are a few options in this step which are effective for glazing such as fiberglass, tempered glass, and acrylic.

Ultimately, the main idea is to increase the sun’s heat through the cover and ultimately reduce heat loss simultaneously. Tempered glass is quite a popular option due to its ideal characteristics for this purpose. 

Step 6

This step involves determining the efficiency of the system and working on those details. If you are using an old electric heater, you need to strip off the outer enclosure and insulation and get rid of the old pipe fittings as well as check the inside for sediments.

If necessary, clean the tank. In order to increase the heat absorption, you need to paint the tank in flat black. 

In this step, you also need to install the pipe fittings, drain and pressure release valve.

Seal all exposed surfaces by running silicone along joints and connections, install connectors to concentrate the sun’s light, including insulation or shutter at the top for heat loss protection and your homemade solar water heater is ready to use.

How do I install my DIY Solar Water Heater?

What you’ll essentially be doing is circulating solar heated water through a continuous loop of plumbing that runs from the roof-mounted panels down to a heat exchanger.

This would be done via a pump and back to the panels again. The heat exchanger is basically a tank within a tank that transfers the approximately 140°F warmth of the loop water to the cooler supply reservoir surrounding it. 

Fittings tapped into that reservoir allow it to be placed inline between the city water source or well that your house is fed by and the cold water inlet pipe to your electric or gas water heater. 

However, we suggest that if you don’t know much about plumbing, then you should basically get advice from a plumber or even hire a professional plumber to get the installation done for you. This will ensure that it is done correctly. 

Can I plug the solar water heater into my hot water heater?

Yes, it is indeed possible to plug your solar water heater into your hot water heater tank. Basically, you need to configure such a system to supplement your hot water by routing the cold water from the water heater tank.

It works best in moderate climates because heat is bound to radiate from the pipes when it’s cold outside. 

Can I plug the solar water heater into my central heating system?

Yes, solar water heating systems use the radiation from the sun to heat water in a panel which is often situated on the roof and this, in turn, supplies the heat as hot water, or it can be connected to a central heating system.

Ultimately, it will generate electricity that can be used to power the solar heating pump. 

Where can I get parts?

Most of the parts needed can be found at your local hardware store but if you need a head start, we’ve found Renogy’s parts & pre-made panels to be an excellent choice!

renogy solar product supplier

Find incredible deals & discounts at Renogy Solar Supply.


Solar water heating systems are one of the best ways to decrease energy costs associated with heating water. This is especially when using electricity to heat water at home, which is one of the most expensive ways to do so.

When you use solar power, the sun’s energy is used to heat water which is stored in a hot water tank and drawn on when required winter. Ultimately though, it is one of the best ways to reduce the amount of money you’re spending on energy bills, and lowering your carbon footprint on the earth.

author avatar
Charlie Hardcastle


On Key

Related Posts

Is Drano Bad for Pipes? The Truth Revealed

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases. When it comes to dealing with clogged drains, many homeowners turn