Solar Thermal: Frequently asked questions

General questions | Questions about Solar Thermal

General questions about solar energy systems back to top of page

What's the difference between the two types of solar energy systems?
Solar Thermal panels heat water using the warmth of the sun and then transfer the heat collected to your domestic hot water system, whereas Solar Photovoltaic (PV) systems are "solar cells", using the sun's light to generate electricity for use in the home. Excess electricity can also be exported to the grid if sufficient is produced.

Is my home suitable for solar energy?
The basic minimum requirements for both solar water heating and PV systems are much the same, calling for unobstructed exposure to the sun during the brightest part of the day - typically between 9am and 3pm – and the opportunity to mount the panels or cells at an angle around 20-50 degrees to get the most benefit. A south-facing roof which enjoys direct sunlight during the two hours either side of noon is particularly ideal.

Will the system work at night?
No, the system only works in daylight. At some times of the year there will be insufficient daylight and that is why your systems have a fossil fuel back up that will cover your needs at these times.

How much roof-space will it take up?
You'll typically need to allow about 4 square metres of available roof-space for solar water heating panels, while a PV system will demand three or four times as big an area.

Will I need planning permission?
For the majority of homeowners the addition of solar panels fall within 'permitted development rights', which means that the panels will be more or less flush with the roof. If your property is in a conservation area, an "Area of Outstanding Natural Beauty" or is a listed building, you may need to apply for full planning permission. We recommend checking with your local council to see what their position is on solar panels.

How long does a system take to install?
Installation time depends on the size of the system. Average residential systems rarely take more than 2-3 days to complete.

Who will install the system?
Our installation partners have team of fully MCS (Microgeneration Certification Scheme) accredited installers for the installation of both solar thermal and solar PV systems. The MCS is an independent scheme that certifies microgeneration products and installers in accordance with consistent standards and is designed to evaluate both products and installers against robust criteria providing greater protection for consumers. An MCS approved installer must be used in order for the householder to qualify for the government grant or the Feed in Tariff.

Do you sell both types of system?
Yes, we sell both types of solar systems: Solar photovoltaic (PV) systems which generate electricity from daylight and solar thermal systems to heat water.

What about insurance and storms?
If you buy solar panels and add them to your house, your insurance company will be obligated to insure them, just as they insure the rest of your household items. You should take sensible precautions against storm damage, but of course rooves are naturally more susceptible to this kind of damage.

Will solar systems add value to my home?
Solar systems of either kind can increase the value of your home by an average of 9% (source: The Guardian). Research carried out by The Energy Saving Trust confirms that 85% of buyers will pay up to £10,000 more for the same property if is more energy efficient. Solar technology has never been more affordable, and the cost is subsidised by government grants - money that would be going to the energy companies.

Is the UK suitable for Solar Energy?
Yes – MyPlanet Solar Thermal products use the latest technology, which has been designed specifically for the northern hemisphere and European climate. These do not need direct sunlight to produce energy as they work on irradiated light (natural daylight). So even on a cloudy day our hot water panels will still produce hot water.

Questions about solar thermal energy systems back to top of page

What is Solar Thermal?
Solar collectors come in the form of either evacuated tubes or flat plates, and are used to absorb thermal radiation produced by the sun during daylight hours. The clever design ensures that 90 to 95% of the energy which falls onto the collector is absorbed and the heat is passed to a transfer fluid that flows within the plate. Evacuated tubes work in a slightly different way. The heat absorbed from daylight causes a special fluid contained within the heat pipe to boil. This vapour enters a condenser, where the heat is passed to the transfer fluid. In both cases the hot transfer fluid passes heat to the domestic hot water system.

Can I use it for heating radiators?
Thermal solar panels can supply up 70 % of an average household's domestic hot water needs, but is not suitable for heating radiators. However, It can be used for space heating and swimming pool heating. A standard system for a 3 bedroom house would consist of 2 panels and a twin coil cylinder together with the associated hardware to integrate the parts. For larger households larger cylinders and more panels are required. We will advise you of requirements during our site assessment.

How do solar thermal systems work?
The system consists of a solar collector, a pump station, a controller and an indirect hot water storage tank. The solar collector collects the sun’s energy and transfers the heat to the storage tank via the tank’s internal heat exchanger. The storage tank allows the hot water to be stored until it is used. The storage tank acts as a pre-heat tank for the existing hot water tank. As hot water is being drawn from the existing tank, hot water from the pre-heat tank replaces it.

What are the benefits of a solar thermal system?
There are several benefits:

You can produce up to 70% of your annual hot water requirements

You will reduce and "future proof" your fuel bills. Sunlight is free so once you have paid for the initial installation, your bills for producing hot water will be significantly reduced for the lifetime of the system (around 25 years)

You will reduce your carbon footprint. Solar hot water systems use the renewable resource of the sun and do not release any harmful carbon dioxide or other pollutants. (The small amount of electricity used to power the pump is negligible)

What is the difference between flat panels and the glass tube type collectors?
They are both normally roof mounted, and they both do roughly the same job of heating the water. However, evacuated tube collectors are easier to install, and because they are better insulated they are more efficient in low sun conditions. They are also better at absorbing solar radiation at different angles to the sun and are easier to clean / maintain. However, flat plate collectors are typically cheaper, and some may perform better on cloudy days – and some people choose flat panel collectors based on the looks.

What is a Closed System?
A Closed System is one where the liquid warmed in the collector is used to warm the hot water tank via a heat exchanger or coil in the tank. An Open System directly heats the hot water, and this approach is more common in warmer climates where freezing conditions are not common.

Will the system still work in the winter?
Yes, even a sunny day in November will contribute to your hot water, as the system works on sunlight rather than heat. December and January are usually the only two months that your system will rely on the boiler to heat your hot water, as these are the two months of the year with least sunlight.

How safe are Solar Thermal systems?
They are totally safe.
The collectors continue to operate efficiently at temperatures far below freezing.
The only material in contact with the water is copper, which is non-toxic.

Do these systems need much maintenance?
No, in fact generally these systems are maintenance free. Some systems installed in the 1970s are still running. It may be necessary to exchange the antifreeze every few years. It may also be necessary to exchange the pump as it wears, but it’s a normal off the shelf heating pump, and is inexpensive.

What is the life expectancy of a solar thermal system?
The life expectancy is between 20 and 30 years. If a solar thermal system receives regular maintenance checks, they can last over 30 years. Although very little maintenance is required, it is recommended that a service contract be made with your solar installer.

What should I do if it snows?
Absolutely nothing. If snow collects on the glass surface of the collector it will rapidly melt. In fact the design is such that it will melt more rapidly from the collector surface than it will melt on other parts of your roof.

Is performance affected by bird droppings, leaves or grime on the collector?
There is no need to wash or clean the collectors. Deposited grime will not significantly impair performance and when it next rains deposits will be washed off.

Do I need to switch off the Solar System when I go away on holiday?
No - it is better to keep it on.

What is the Renewable Heat Incentive Tariff (RHI)?
The RHI is similar to Feed-in Tariffs, which have done more than anything else to accelerate the installation of renewable energy capacity in Europe. in April 2011 the Renewable Heat Incentive will come into force.

You may earn a regulated income from every kilowatt hour of heat produced

The Tariff level is set by the government - based on technology and size

All renewable heat generation – domestic or business - qualifies for the tariff, with no maximum size.

Under this tariff it is planned that Solar thermal will earn around 6p for every kilowatt of heat produced. All income will be tax exempt.