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Solar Thermal Panels: Free Hot Water

Updated on September 10, 2015
stephhicks68 profile image

Stephanie is always looking for ways to lighten her carbon footprint. She is enthusiastic about solar power and solar gadgets.

Free Hot Water with Solar Thermal Panels

One of the easiest ways to make the switch to renewable energy in your home or business is with a solar hot water system. Solar thermal panels allow you free, nearly unlimited hot water for bathing, laundry, dishes and endless commercial uses. Homeowners often install solar panels to heat swimming pools and spas.

On the commercial side, some car washes now use solar hot water. Breweries and garden nurseries are also among businesses that can benefit from cheap hot water from solar thermal panels. Green hotels and spas also cut their massive energy usage by using solar energy to heat water required for a myriad of uses - pools, washing sheets and towels, and guest bathing requirements.

Compared to solar electric (photovoltaic or PV) panels, solar thermal panels are typically more affordable, and your return on investment is shorter. Not only that, but solar hot water systems are eligible for a number of government rebates, tax credits and other incentives. Solar power is going mainstream these days as people look to save money, as well as the planet!

Ready to consider tapping into free hot water with solar thermal panels? Read on!

Solar thermal panels for free hot water
Solar thermal panels for free hot water | Source

Why Switch to Solar Hot Water?

If you are looking to save energy and money, one of the biggest power hogs in the home is an electric or natural gas hot water system. With solar thermal panels and a specialized solar hot water tank, you can instantly see a reduction in utility bills for little money upfront.

In fact, solar hot water systems are both cheaper and more efficient than PV solar panels. When you consider federal and state tax incentives, credits and rebates, homeowners can recoup their investment in as little as two years, although the average ROI is about 4-8 years. Because solar thermal collectors use radiant solar energy, they are more than three times more efficient than photovoltaic panels. That means for every hour of sunlight, you are able to convert three times as much energy for use within your home or business.

The California Energy Commission estimates that, by installing a solar hot water system, the typical household can cut 60-70% off their annual water heating expenses!

Solar Powered Hot Water for Your Home

Components of a Solar Hot Water System

There are several components of a solar hot water system, none of which are too complex. If you hire a professional to help with installation, you can have free hot water within a day.

Generally speaking, you need the following:

  • Solar thermal panels (also known as solar collectors)
  • Mounting system for the solar thermal panels - they are usually installed on rooftops
  • Solar storage tank - in other words, your new solar hot water tank
  • Water pump and controls (not required for passive or thermosyphon systems)
  • Heat exchanger and expansion tank (only for closed-loop solar hot water systems)
  • Isolation valve
  • Backup Water Heater
  • Tempering valve - to make sure your solar heated water doesn't get too hot!

How Does a Solar Hot Water System Work?

Depending on the type of solar thermal panels (solar collectors) and solar hot water system you install, the mechanics of heating water with solar energy are fairly simple. Two general types of solar hot water systems exist: passive and active.

As the name implies, a passive solar thermal panel hot water system does not require pumps, but rather uses thermal dynamics to move hot water through cold water (heat rises, remember?) With an active system, you need electrical pumps and controls to move cold water through the solar thermal panels into the storage tank. Additional equipment means more expense and maintenance.

Let's start with active/pump-driven systems, of which there are two from which to choose for residential purposes: direct or indirect circulation. In warm climates, direct circulation systems simply pump the cold water through the solar thermal panels where radiant heat from the sun warms it. From there, the water is pumped into the holding tank for use. Since the water is heated directly by radiant energy, it is called an "open-loop " system.

If you live in a colder area of the world where freezing temperatures are often experienced, use an indirect active pump system. Instead of water pumped through the solar collector, a heat transfer liquid (which resists freezing) circulates through the panels as well as a heat exchanger, gets warmed and then transferred to the storage tank where the water is heated by the warmed-up heat transfer liquid. These are often called "closed-loop " systems.

With passive solar hot water systems, no pumps or other mechanical devices are required, which often make them cheaper and more affordable for homeowners. Again, there are two general types of passive systems: batch systems (also called Integral Collector Storage, or ICS) and thermosyphon (also spelled thermosiphon) systems.

The latter are the more commonly used by households. They rely on thermodynamics and require both the solar collector and storage tank to be placed on the rooftop (hot water rises from the panels to the storage tank).

No matter which type of solar hot water system you use, most people keep a back-up hot water tank for days where there is low UV light and/or when solar energy cannot heat enough water for your requirements.

What Types of Solar Thermal Panels are Available?

There are several types of solar thermal panels that can be used with solar hot water systems. Like the systems themselves, the panels you select will depend on your climate and hot water needs.

Flat-plate solar collectors look much like their PV solar panel cousins. Unglazed, flat glass or plastic plate coverings fit over an insulated box in which a dark absorber plate is placed. These solar thermal panels are often used for swimming pools and spas.

ICS or Batch Collector-Storage panels are characterized by black tanks or tubes, also in an insulated box. As cold water passes through the tanks or tubes, it is warmed by radiant energy, and from there flows toward the storage tank for use.

Evacuated tube solar collectors are commonly used for commercial solar hot water applications. They consist of parallel rows of glass tubes and also include metal absorber tubes attached to a fin.

Commericial Solar Water Heaters in China

Why Install Solar Thermal Panels for Free Hot Water?

There are many reasons you may want to use renewable energy to heat the water for household domestic uses:

  • Protection against rising electricity and/or natural gas costs
  • Pay for the cost of the system only, and not for the energy to heat water
  • Quick return on investment (ROI) in a matter of years
  • Adds value to your home
  • Live with a smaller carbon footprint
  • Federal, state and/or local rebate and incentive programs help defray the costs and lower your tax burden
  • Low maintenance over the life of the system (about 20-30 years)

There are a number of DIY solar hot water systems available.  It can be a relatively simple weekend project, depending on the type of solar collectors you select, and whether you are going with an active or passive system.

For closed-loop systems and those requiring pumps and heat exchangers, it is recommended that you hire a professional solar thermal system contractor.  Paying just a bit more for the service can save you headaches later.  Contractors can even help you maximize your tax savings or apply for rebates!

Would You Consider Installing Solar Thermal Panels on Your Home?

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© 2011 Stephanie Hicks


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    • profile image

      oulande Mendy 

      20 months ago


    • GetitScene profile image

      Dale Anderson 

      21 months ago from The High Seas

      This is an excellent hub, well done! It is information that more people need to know and be called to action on. I am using a contact of mine to have a solar water heater installed in my good friend's sisters house o heat both her pool and her household water.

    • profile image


      4 years ago


      We have 4kw solar on roof for house and Evac Tubes (30) for 315ltr HWService.

      We run the house and an 8 X 4 Mtr pool out back. ALl yr.

      and get around $650=700 cash returns every yr from power company.

      If I heat the pool for winter ?(around 12 weeks) it costs around $1100 minus the $650 ish, to keep it at 30/32 deg living in Central Queensland Australia.

      Anybody who does NOT have solar in a home they keeping long term is a financial fool. Prices are only going up.

      I've been using solar on yachts and caravans since the '70's.

      A coupla rolls of 100mtr 10/12/15mm blackpoly hose laid out in back garden up here.linked to a low pressure 12v pump and coupled to water system in pool also helps it along too.

      Solar panel. Battery. small in line 12mm 12v pump and switch for isolating.

      self sufficient too.

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      7 years ago from Bend, Oregon

      Hi Mary - thank you! Please feel free to link to your solar lights hub. I'm off to go give it a read. Cheers, Stephanie

    • mary615 profile image

      Mary Hyatt 

      7 years ago from Florida

      This Hub is a related one to the one I just published on using solar lights for a pathway to replace low voltage lights. This is a very informative Hub. I voted it UP, etc. and I'd like to share.

      May I link this Hub into the one I just published? Check mine out when you have some time.


    • profile image

      renewable sources 

      8 years ago

      Solar panel system has gained lot of popularity in the recent time, as it has been proved as the best alternative source of energy. It also helps in saving money from the electricity bills. Nice article, thanks for sharing.

    • Spirit Whisperer profile image

      Xavier Nathan 

      8 years ago from Isle of Man

      What an excellent hub! You have explained it all so clearly and it sounds as if you guys in the States have made it an accessible option for the ordinary Joe blog to afford. We are still very behind you over here and I am looking forward to the time when every house creates its own electricity naturally like this. Thank you. Voted up useful and awesome.

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Thanks LRC - these are so affordable! We were on vacation and the property was complaining about the cost to heat the swimming pools - solar hot water makes a ton of sense.

    • LRCBlogger profile image


      8 years ago

      This is something I have been considering (how to make my home more green friendly). Thanks for the great info

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Thank you prasetio! I am a big supporter of solar energy, and any other renewable resource that can reduce our use of fossil fuels. Best to you, Steph

    • prasetio30 profile image


      8 years ago from malang-indonesia

      Nice information and very inspiring us. I know we need alternative energy to support our life to replace fuel energy. Solar energy is one of the best. I learn much from you. Keep it up. I give my vote to you. God bless you. Cheers...

      Love and peace,

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Thanks Mike! I hope that more people adopt solar energy too!

    • Mike Outdoors profile image

      Mike Outdoors 

      8 years ago from Somewhere in Canada

      Very interesting. I wish more people would adopt solar energy.

    • profile image


      8 years ago

      Great info, nice hub, thanks for sharing, thumbs up :)

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Hi Audrey - thank you! We get so much sunshine in Central Oregon that it only makes sense to consider solar power. We are thinking about one of the solar leases (for PV power) that are now offered in Oregon too. Do let me know if you install solar at your home! I'm very interested!

    • profile image


      8 years ago

      Wow, that was the longest hub I've ever come across! :D

      Good information here, we should all switch to more renewable energy components whereever possible and affordable.

    • akirchner profile image

      Audrey Kirchner 

      8 years ago from Washington

      We're due to have an energy assessment but have to wait until APRIL - you have to be kidding me because our square footage was too great for the February slot. This sounds a little ridiculous to me...but all that aside, I'm going to be asking some serious questions about what we can do (that we can afford) to make our home more energy efficient and cut the high costs of utilities.

      It seems to me between the sun here and the wind on our ridge where we live, we should be able to get something going!! Of course then pops up that annoying question, can we afford it - but we shall see!

      Great piece as always and I love that you are so pro-environment!

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      I hear you Jeff! Same here!

    • Jeff May profile image

      Jeffrey Penn May 

      8 years ago from St. Louis

      Good info. I've always thought I'd have a solar powered home, then I got married and had kids and embraced the full catastrophe.

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Hi Darski - you are right that solar is getting more affordable these days. I hear you about limited income and I wish that there were more programs for people like you. You can guard against future utility rate hikes with solar, though, as you noted. Peace and love to you as well! Best, Steph

    • Darlene Sabella profile image

      Darlene Sabella 

      8 years ago from Hello, my name is Toast and Jam, I live in the forest with my dog named Sam ...

      My friend, I have been thinking about solar for months now, except I am a senior on limited income, I really need this for the future of cost of Utilities and all the other bills. This has been around for a long time, and finally getting a wee bit affordable. I want to learn as much as possible and thank you so much for this excellent hub. Rate way up love & peace darski

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Thank you Robie! Yes, its helpful to understand the mechanics of a solar hot water system. For families like mine that use a fair amount of hot water, it makes perfect sense. Cheers, Steph

    • robie2 profile image

      Roberta Kyle 

      8 years ago from Central New Jersey

      What great information on thermal solar panels. You explain it all so well. I think I now understand how it works. If I didn't have a very efficient little on demand water heater I'd consider going with solar. Great and very informative hub

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Thanks NN! For people thinking about going solar, this is one of the easiest and most affordable ways to use renewable energy.

    • profile image

      Nancy's Niche 

      8 years ago

      Excellent information; love the idea of the solar thermal panels. Thanks for sharing this information…

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Hi Dallas and Gordon - there is a lot of potential for this type of solar energy. Even in Scotland, Gordon! Bright, fully sunny days are not required for effective solar hot water systems. Just a bit of UV light.

      I appreciate the comments, as always! Best, Steph

    • Gordon Hamilton profile image

      Gordon Hamilton 

      8 years ago from Wishaw, Lanarkshire, United Kingdom

      Fabulous information, Steph. It is important for people who have alternative energy options and solutions to make the most of them and look at different ways to use environmentally friendly resources. My only problem with solar power is that - in Scotland - it would be Christmas 2014 before I had enough hot water to make a cup of coffee... :)

    • dallas93444 profile image

      Dallas W Thompson 

      8 years ago from Bakersfield, CA

      Lots of great information. Thanks for sharing. Thumbs up and useful!

    • stephhicks68 profile imageAUTHOR

      Stephanie Hicks 

      8 years ago from Bend, Oregon

      Hi kashmir and Dexter - thank you so much! I often publish on solar power topics and the idea of solar thermal panels and solar hot water is so great. Cheaper and more efficient than PV solar electric panels. Its a great way to save money and the environment too! Cheers, Steph

    • Dexter Yarbrough profile image

      Dexter Yarbrough 

      8 years ago from United States

      Great information. Thanks!

    • kashmir56 profile image

      Thomas Silvia 

      8 years ago from Massachusetts

      Hi stephhicks68, all great and much needed information and ides to help save money heating your home and your water .

      Awesome hub !!!


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