Fitting a solar water heater

Last updated Monday 21 July 2008

The good way to get yourself in hot water

Fancy using sunlight to cut your hot water bill? A solar panel on your roof could provide about a third of the hot water your household uses every year.

Solar water heaters use the sun's energy to pre-heat the water in your tank. When the fossil-fuelled boiler kicks in, part of the work has been done already so it can knock off early.

The set-up doesn't come cheap: a family of four would need to shell out about 4,000. The good news? Grants are available to cut the cost.

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Photo: Fitting a solar water heater

Saves up to 330kg of CO2 a year

251 Bloomers are doing this

CO2 reduction 2 out of 5

Cheapness 5 out of 5

Popularity 3 out of 5

Cost 3,200 - 4,500

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How does it work?

Pub Fact

  • About 100,000 households in the UK have solar water heaters fitted
  • The average person in the UK uses 55L of hot water per day
  • Total water use is climbing by 1.5-2% per year
  • Today, solar energy accounts for only 0.1% of our energy portfolio
  • Total solar energy received in December is a 10th of that received in June

A roof-top panel soaks up solar energy. Most systems then heat a fluid that is fed through an element into your hot water tank, warming the water before your boiler fires up.

There are two main designs. Flat plate systems consist of an absorber plate with a transparent cover. The more expensive evacuated tube systems are comprised of a row of glass vacuum tubes, each containing its own absorber plate. This set-up is more efficient because it reduces heat-loss in the system.

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How will it make a difference?

A solar water heater will meet a third of the annual hot water needs of a three-bedroom house, and most of your hot water during the summer, potentially cutting your bills by about 40 a year.

It will reduce CO2emissions by around 330kg per year in a gas heated home (more than six times as much CO2 as turning your gadgets off standby) - and still more if you're using other heating fuels.

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How do I do it?

  • Identify at least 3-4 square metres of un-shaded, south-facing roof (south-east or south-west is good enough)
  • Get planning permission if you need it. See the official Planning Portal
  • Make sure your house is insulated - otherwise you won't get a grant from the Low Carbon Buildings Programme
  • Find out whether your existing hot water system is compatible
  • Contact an accredited installer through the Low Carbon Buildings Programme
  • You need to install a temperature controller as well if you want to avoid scalding hot water in the summer months

If you're feeling particularly ambitious, you could try making your own solar heater for less than 3 (see TreeHugger) but be careful to avoid brewing a bacterial soup.

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What's the debate?

Solar thermal panels have a high embodied energy - in other words, a lot of energy went into making them in the first place.

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What's stopping me?

"I don't have a hot water tank - won't I need one?"

Yes you will. Check with the installer - a tank might still be compatible with your existing boiler, but it will make the whole business more expensive.

"They're an eyesore!"

It's probably a question of taste. But even if they don't make your roof any more handsome, once fitted these systems require little maintenance and should last at least 20 years. So you'll have plenty of time to get used to it.

"They cost how much?"

It's a fair point - but check out those grants before you dismiss the idea. Researching the market will help you find the right kit at a good price. Shopping around could also protect you from paying inflated installation fees.

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When should I do it?

Fitting will be better value if you're already replacing your boiler or roof. Savings increase when coal, oil and gas prices are rising.

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David, Thurrock 2009-05-06

I have built and installed my own solar hot water system for about £600. It has become a full time hobby keeping a day to day diary of results that are published on my website ( At the current date ( May ) we are just about getting all our hot water for free

Anonymous, Antrobus 2009-03-06

I managed to source a solar heeting system for less that 1000 brand new ( I am currently installing it my self which seems easy enough (I am just a standard DIYer). I'll let you know how good the system is once it is finished.

Roger, Gloucester 2009-01-07

I made my first flat plate solar water heater 35 years ago using scrap copper pipe and old cylinders for the backing plate. It was very successful, operating on the thermosyphon principle. It was passed on to another family 3 years ago and is still going strong. I subsiquently made a second one mounting it on a turn table so the I could track it round to follow the sun. In full sun during summer I was able to heat a standard cylinder of water three times in a day to a temperature too hot to touch. 7 years ago I purchased a Thermomax system which I installed myself. It increases the water temperature even in the rain in winter. In full sun the temperature can easily reach 50 C, at which point a valve opens and solar water is fed direct to the taps. It has proved to be well worth the effort.

Shaun, Wombwell, UK 2008-09-09

Actually did this in summer 2005. We get a FULL tank of (on average) 25 to 50 degrees C water every day of the year. Cloudy or not. Any further heating is done by our super efficient condenser boiler, and we're saving a fair bit of money. Relatively cheap but very efficient.

Anonymous 2008-08-29

Dead easy to buy and have installed. Don't know why we waited so long - instant hot water every day (even when cloudy).

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Glossary terms used on this page
CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
Embodied energy
Embodied energy - sometimes referred to as 'embedded energy' - is the energy used (and therefore the CO2 emissions) in manufacturing, packaging and transporting a product, material or service. So when calculating the CO2 savings from a new energy-efficient product such as a boiler or washing machine, its embodied energy needs to be taken into account. Usually the energy saved in use will quickly compensate for the embodied energy, but in some cases - such as small urban wind turbines - it may be that a product will use more energy in its manufacture than it will save across its lifetime.
Emissions are the CO2 (and other greenhouse gases) produced by energy use, usually calculated and stated as an annual tally: also referred to as your carbon footprint. Your personal emissions can be direct - such as the gas you personally use to heat your home or the petrol you burn to power your car - or indirect - meaning the energy use that has gone into the products or services you buy. The latter, such as the emissions caused by the manufacture of your new TV, or the packaging your food comes in, are also referred to as embodied emissions.
Fossil fuels
Fossil fuels are the deposits of crude oil, natural gas and coal formed by the decay, over millions of years, of organic material (plants, trees animals and bacteria). Because the combustion of fossil fuels releases carbon that has been out of the natural carbon cycle for so long (unlike with living or more recently dead organic matter, known as biomass) it affects the balance between stored carbon and carbon present in the atmosphere as CO2, a greenhouse gas.
Planning permission
Planning permission is consent, usually from a local council, to build on land, or change the use of land or buildings. Significant structural change, such as that often associated with microgeneration projects, is likely to require planning permission. Changes to listed buildings require additional, separate consent.
Solar energy
Energy derived from the sun's rays.
Solar energy
Energy derived from the sun's rays.
Solar water heater
A solar water heater uses the energy of the sun directly to heat a fluid that is fed into your hot water tank, meaning your boiler has less work to do (and requires less energy) to get your hot water to the required temperature. navigation


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