How Solar Water Heaters Work

roof mounted solar water heater
By Greg Whitburn

Water heating accounts for 30% of energy consumption, so is a great place to begin cutting back on fossil fuel consumption.

What's more, solar water heating can be added fairly easily to homes... Let's explore...

There are a number of options for a solar water heater; from purchasing ready-to-roll systems to making your own.

The basic model is that the sun’s energy is used to heat water. The process is called solar-thermal – conducting the sun’s energy as heat, as opposed to photovoltaic – converting the sun’s energy into electricity.

How do solar water heaters work?

roof mounted solar water heater
Roof Mounted Solar Water Heater - Cold water flows into the tubes, is heated by the sun, and flows out to an insulated cylinder.

A module of solar tubes is installed on a roof or sun-exposed area. Cold water passes through the tubes and is heated by the sun, flowing to an insulated cylinder once heated.

Alternate systems use chemicals such as glycol, which are easy to heat. The glycol flows through the solar tubes, then heats the water.

Most solar water heating systems require an electric powered backup heater known as a booster. The booster kicks in to further heat the water and kill any bacteria, or at night time and cloudy days when the system isn’t getting enough sun energy.

Some systems carry the water to a storage cylinder inside the house, whereas some storage tanks are outside (often connected to the solar module), or in the ground. The advantage of having the tank inside is better insulation. The advantage of outside is that installation is simpler and cheaper for retro-fitting.

There are also differences in how the water gets to the cylinder. Convection solar water heating systems use convection current principle - that hot water rises – to transfer hot water to the cylinder. This method stores the hot water above the module and doesn’t require any mechanics or electricity. Pump based systems use an electrical pump to transfer the water to the cylinder.

Buy solar water heaters or make your own?

Solar water heaters can be purchased as a package and installed by professionals or you can make your own.

The main advantage of a professional job is knowledge and experience; your solar water heater system will be tidy, installed with best practice, made from materials that have been tested and proven to last, be installed in the optimal spot for maximum sun exposure, and will likely come with some type of guarantee.

The downfall of using professionally made solar heating systems is expense.

There are large communities of people on the net who make their own alternative energy mechanisms, and many of them have instructions for building your own solar water heater.

It’s highly recommended you do some due diligence before diving in to either option. Installation is a big task so you only want to do it once.

Things to consider

Price: Never just go for the cheapest option, but have a look around and get a feel for prices, including installation and maintenance fees. Often sourcing locally is the best option as there’s easier access to follow up support, but have a look on the internet as well and get a broad gauge of the prices and packages available.

Kitset or pay for install and maintenance? If you’re an experienced tradesman you may be able to purchase from a company then install a solar water heater yourself. In this case you’ll be able to save a lot of money, but check with your dealer whether they offer product-only sales.

How much hot water do you need? A family of four uses a lot more hot water than a family of two, so make sure you’re thinking literage when you’re looking at your solar hot water options.

Solar company reputation: Take your time to get as much information as you can about your chosen solar hot water company. Look on a number of websites and read as many customer reviews as you can.

Your solar company should be happy to offer a free consultation before you commit. A good thing to consider is whether they can answer your questions without hassle. If they can answer your questions over the phone and without having to look things up every two seconds it’s one indicator that the staff have a good knowledge of solar and offer good customer service. If they tell you to just read their website it may not be a great indicator. Also remember to compare maintenance service and guarantees.

DIY solar reputation: Likewise if you’re building a DIY solar water heater, have a look around and scope out the best plans. Look for plans that have been used by many people and include good feedback. Join forums and learn from the experience of other alternative energy-ites. It’s also a good idea to discuss any plans with a builder, plumber or electrician, and research your local consent requirements.

First published January 10, 2012
Last updated February 6, 2021

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7 comments on “How Solar Water Heaters Work”

  1. I think this article could do with a few more simple diagrams and example pictures to further educate those who seek the "Knowledge" > I also believe that all School children should be introduced to the rudimentary workings and ideals of "Solar Energy" capture in the form of Thermal Radiation technology , to provide hot water to warm and power to light and ventilate their thermal mass homes of the future. But there again many children and their Parents do not live freely due to financial hardship and therefore cannot take advantage of the Sun's "life giving energy". Here in New Zealand avoid the suns rays between September and April from 10am to 2pm to avoid skin problems and many forms of Cancer, yet we have not found an ideal balance of exposure or an alternative solution which would solve the problem of "Vitamin D deficiency" ( as the Sun is mankind's principle source ) and we know that this deficiency cripples a huge percentage of them from birth !!! > TAZman

    1. I have been doing some research on solar panel and wind tuibnre systems. The pricing is crazy. For a 10Kw solar grid tie kit system is between $35,000 and $40,000. If you install batteries add $3,000-$5,000. 10Kw will only power a small to medium home without electric heat. Using my electric usage and info from my local electric company payback is 60 years for solar and 361 years for wind. This is unexceptionable. The manufactures of the solar and wind are gouging the consumers. They are using the excuse of supply and demand for the high cost. When demand goes up so will mass production and the price will go down. This is true, but they are making a huge profit on what they are making now. Some items are in the 3000% markup range. Are the power companies keeping the price up so their profits don't suffer? My local electric supplier has an ENERGY PARK that you can go see solar and wind power in action and check out real time data online. They have a 4Kw solar array installed and claim it cost $30,378 installed and a 2.5Kw wind tuibnre that cost about $20,000 installed. I think they are giving false numbers to consumers so you won't go green. I was able to find a 3.5Kw kit online for $9,000. This doesn't include any type of mounting materials. You can add $800-$1,200 for these materials. An installer will will charge you $2,000-$4,000 to install it. For the sake of argument lets say this will cost you $15,000 to install but still way out of line for you and me to install. That is a far cry from the $30,000 the power company claims. The power companies don't want you to make your own electric. They are keeping the cost high so they will still make money off you. A 210w panel sells for around $600. They probably manufacture it for under $50. The cost needs to be $100-$150 to the consumer to make it affordable to the average home owner. 50 210w panels make a 10Kw system. That would be $5,000 not $40,000. The manufactures are raping us and the power companies are helping them to keep prices high. When will we get the technology at a proper cost? Let me know what you think.In response to the first 5 answers, Yes, if demand increases so will mass production and thus supply will increase and this will drive the price down. I looked into panels from China. From what I was able to find panels sell for $0.17-$0.45 per watt. In the U.S. they sell for $3.00-$5.00 per watt. Manufactures in the U.S. have lobbied for a higher tariff on solar products that makes them impractical to import on mass. These companies want to keep the price high so their profits stay high, and the power companies do not want you to produce all your own power. That would put them out of business.In response to Steve R, You need to do more research before you post another retarded comment like that. Air DOES have mass (just not very dense). When air is in motion it is called WIND . This motion creates energy. Have you ever heard of a tornado ? Get your facts together next time.

  2. Thanks for the suggestion TAZ, good point. More diagrams is on the to do list, so we'll include some for this page too.

    Absolutely, all renewables should be part of education (as should environmental awareness & resource efficiency). I hope and expect that this will become the case as renewables gain momentum. As well as being important for the future, solar is a great real world example to teach students about chemistry, physics etc in science classes.

    I agree on the financial difficulties - ideals are nice but reality can be difficult. Economics are the the biggest factor holding renewables up, naturally. And of course politics plays a huge role in economics. There's a ridiculous amount of development going on in so many areas of renewables today (and over the last few years), so I can only envisage a future where renewables are a massive piece of the energy/education puzzle... one way or another.

    Thanks for all your comments on all our posts, it's good to get some reader discussion.

  3. by heating a water in solar water heater what is a benefit for our body like skin or any other disease ?

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