Solar Thermal Panels and Solar Water Heating

Solar thermal panels use the sun’s energy to provide hot water for your home.

They won’t provide all your hot water but they will make a modest dent in your bills.

The government pays you for the energy your panels produce, so you benefit twice.

 


What's In This Guide to Solar Thermal Panels?


 

What Are Solar Thermal Panels?

A solar thermal system uses warmth from the sun to heat water for your home or business.

Solar thermal panels are usually made of tubes, called collectors, that are filled with liquid which is warmed by the sun’s heat. The warm fluid is then pumped through a coil in your water cylinder, warming your water up.

A boiler or electric immersion heater can be used to top up the temperature of the water if it isn’t high enough, or to provide hot water at night. Solar water heating cannot provide all your hot water; the Energy Saving Trust estimates that it will provide about 60% of it. But that still reduces your fossil fuel consumption and hot water bills by more than half.

On top of the savings you make, the government also pays you for the energy you generate through a scheme called the Renewable Heat Incentive.

a diagram showing how solar thermal panels work

 


 

Types of Solar Thermal Panel

There are 2 main types of solar thermal panel: flat plate collectors and evacuated tube collectors. The difference is in the way they are designed:

Flat plate collectors have a plate inside an insulated box which absorbs the sun’s heat. The fluid is pumped through tubes inside the plate, which warms it up.

Evacuated tube collectors have 2 sets of tubes instead: outer tubes made of glass, and inner tubes made of either metal or glass which the liquid is pumped through. The outer and inner tubes are separated by a vacuum.

Evacuated tube collectors are usually more efficient, because a vacuum is an excellent insulator. So an evacuated tube collector will provide more heat than a flat plate collector of the same size. For this reason, flat plate collectors tend to be cheaper and some people also prefer the way they look, as they can sometimes be integrated into the roof.

 


 

Benefits of Solar Thermal Panels

Free hot water.  Sunlight costs nothing, so once you’ve paid for and installed the panels, all the energy you get from them is free.

Solar energy can never run out. The system will work best in bright sunlight, but it will generate some power whenever there is daylight, all year round. And you still have a source of hot water if your gas or electricity goes off.

They’re environmentally friendly. Using solar hot water does not produce pollution or add to global warming.

Low maintenance. Solar panels need little maintenance. The Energy Saving Trust recommends having your system checked over by an accredited installer every 3 to 7 years – your installer should give you guidance on this. Most solar thermal systems have a 5 to 10-year warranty.

Disadvantages of Solar Thermal Panels

Their efficiency will vary. The panels will produce less energy on a cloudy day, and none at night; you will still be partly reliant on fossil fuels. If your roof doesn’t get a lot of sun, solar thermal panels won’t be suitable for you, because the expense will not be worth the return.

You need a suitable hot water cylinder. You’ll usually need a special solar cylinder with 2 coils, either as a replacement for or in addition to the one you have right now. If you don’t have a hot water cylinder, you’ll have to think about whether you have space for one.

They’re not easily compatible with combi boilers. It can be done, but since the main advantage of a combi boiler is that it only heats the water you need when you need it, and saves space by not having a hot water cylinder, adding a cylinder to store water contradicts the advantages of a combi.

 


 

How Much Do Solar Thermal Panels Cost?

You can expect to pay anywhere between £3,000 and £6,000 for solar thermal panels, including parts and installation. The Energy Saving Trust estimates between £4,000 and £5,000 for an average sized system; Which? estimates between £3,000 and £5,000.

The cost of the system will depend largely on its size. As a rough guide, you are likely to need at least 1 square metre of panels for each person in the house.

You can save money by installing the panels yourself, but since you are only eligible for the Renewable Heat Incentive (see below) if you use an accredited installer, this loss will probably undo any savings you make on installation costs.

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How Much Money Will I Save With Solar Thermal Panels?

The financial benefits of solar thermal panels are twofold. You will save money on your energy bills because the sun will be heating your water for free, and you will be paid by the government for the energy you generate.

1) Savings on your energy bills

How much you save will depend on how much heat you get from your solar thermal panels, but it is likely to be a pretty modest amount.

The Energy Saving Trust estimates that solar thermal panels will save you £50 a year if you have a gas boiler, £55 if you have an oil boiler, £65 if you use coal, £80 if you have an electric boiler and £95 if you use LPG (liquid petroleum gas).

2) The Renewable Heat Incentive

This government scheme pays you for the renewable energy you produce for 7 years. You receive payments every quarter.

The tariff changes every 3 months. For April to June 2018 it is 20.66p/kWh of energy (up from 20.06p the previous quarter). Your payments will normally stay the same throughout the 7 years.

Based on figures from the Energy Saving Trust, here are our estimates for how much you can expect to earn from the Renewable Heat Incentive at the current tariff:

Using these figures, a 4-person household would recoup £405 x 7 = £2,835 in the 7 years of receiving the Renewable Heat Incentive. However, after the 7 years is up, the only financial gain will be the money you save on your energy bills.

Number of People in Household
System Size (metre sq.)
Annual Payment
Total Savings with Gas Boiler
Total Annual Gain
2
2
£206
£50
£256
3
3
£278
£50
£328
4
4
£355
£50
£405
5
6
£458
£50
£508
6
6
£499
£50
£549



Is My Home Suitable for Solar Thermal Panels?

Hot shower

The roof space on which you intend to install the panels should ideally face south, though east or west is also okay, and should be in direct sunlight for the main part of the day.

The panels can be mounted onto your roof or built into the roof, which may look better but is more complicated and expensive. They can also be fixed to a frame on a flat roof or even put on a wall.

If you have a lot of appliances which heat their own water, like electric showers and cold-fill dishwashers and washing machines, solar thermal panels may end up providing hot water that you don’t need.

If you live in a listed building or a conservation area, you might need planning permission to install solar panels. Otherwise, it’s unlikely.

The best way to work out if your home is suitable is to get one of our trusted installers to pay you a visit and discuss the options in detail.

 


 

How Do I Find a Trusted Solar Thermal Panel Installer?

Your installer should be certified under the Microgeneration Certification Scheme (MCS), a national quality assurance scheme, and use MCS-certified products.

He or she should also be a member of the Renewable Energy Consumer Code (RECC) or the Home Insulation and Energy Systems Quality Assured Contractors Scheme (HIES). These schemes ensure consumers are dealt with ethically.

 


 

Getting the Best Out of Your Solar Thermal Panels

Make sure your hot water cylinder and pipes are well insulated, to reduce heat loss while the water stands in the cylinder.

Use your boiler and hot water sensibly. Letting the sun heat your water during the day and then having a shower in the evening, for example, makes better use of your solar hot water than letting it lose heat overnight, then firing up the boiler for a shower in the morning.

A larger cylinder will hold more hot water, giving you a bigger supply when the panels have stopped working for the day.

Make sure the temperature of your cylinder reaches more than 60ºC at least once a week to avoid legionella.

 


 

Is Solar Thermal Energy Worth It?

The savings you’re likely to obtain from solar thermal panels will vary a great deal depending on your situation. A small household with a gas boiler will make lower savings than a large household which uses lots of hot water and has a large cylinder to store it in, or one which uses a more expensive fossil fuel such as liquid petroleum gas.

Although it’ll take years to recoup your investment in the panels – as is the case with many energy-saving measures – there are other benefits which are harder to quantify. Some of these are financial, such as the fact that the panels might add value to your house, or that they will lessen the effects of any rise in energy prices. Others are more to do with quality of life, such as the fact that you have a means of heating water if your boiler breaks, or the fact that every time someone moves over to renewable energy, all of us breathe slightly cleaner air.

Solar thermal panels and solar photovoltaic panels are not interchangeable: the former heats water, the latter produces electricity. However, you can get technology for solar photovoltaic panels which allows you to use some of that electricity to heat your water; or you can install both types of panel if you have a big enough roof, as solar thermal panels are not usually that large.

Interested in Solar Thermal Panels?



 

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