Solar PV/Thermal | FAQs

 What is the difference between Solar Thermal and Solar PV?
Solar PV systems use energy from the sun to generate electricity with roof mounted modules. Solar Thermal employs roof mounted collectors to absorb energy from the sun. These collectors are usually connected to the lower coil of a twin-coil cylinder via a sealed circuit containing a special glycol/water solution. The pump in the system circulates the heated fluid from the collector to the cylinder, where the stored water is heated for use in the home.

Do I need planning permission to install a solar panel?
In some circumstances, you may need planning permission to install Solar PV modules. This may be if you live in a listed building or conservation area. You should always check with your Local Authority before purchasing and installing a solar PV system. A flat roof installation will always require planning and a structural engineers report, due to the effects of wind pressure, etc.

What is the life expectancy of solar panels?
Typical Solar PV modules have a life span of over 25 years, but should last much longer since there are no moving parts. 

How can the amount of electricity generated by solar PV system be checked?
With a ‘Grid-connected’ system, any excess power generated is fed back into the electrical supply Grid. If you have an island system, the excess power would be stored in the batteries for later use.

Can i sell the electricity i generate back to the power supplier?
Most electricity suppliers will pay for power fed into the Grid (feed-in) from domestic Solar PV systems. The easiest way to do this is by signing up to a ‘Buy Back’ or ‘Feed-in Tariff’ scheme with your power supplier. There are two main types of tariff available:

• Generation: You are paid for all of the electricity that your solar PV system generates even if you consume it in your home.
• Export: You are paid for just the electricity that is exported back to the Grid and not for any electricity you have consumed.

What are feed in tarriffs?
On 1st February 2010, the Government announced new standard generation Feed-in Tarriffs (FiT) rates due to start on 1st April 2010, which are guaranteed for 25 years. This new payback scheme, results in a shorter payback for Solar PV systems, making them an extremely attractive green option for any home.

PV systems registering with the scheme between 1st April 2010 and 31st March 2011 will benefit from the following:

• Any system less than 4kW on a new build = 36.1p per kW pay-back
• Any system less than 4kW on a retrofit = 41.3p per kW pay-back
• Any system 4-10kW new build or retrofit = 36.1p per kW pay-back
• Any system 10-100kW new build or retrofit = 31.4p per kW pay-back

This means that if you normally pay 12p per kWh for your electricity, you would effectively get both the power consumed for free and the FiT. So on a retrofit system below 4kW this would mean 12p + 41.3p = 53.3p per kWh saving!

Any Solar PV system installed after the 15th July 2009 is eligible for this Feed-in Tariff at the above rate, provided the system uses MCS approved equipment and has been fitted by an MCS accredited installer.

Does the power company and/or the local network operator need to be consulted before installing a Solar PV system?
It is recommended that you contact your energy supplier before you purchase and install a Solar PV system, a they may wish to fit an additional meter. You should also enquire about green export/feed-in tariffs. There are several now available through different suppliers, so it is advised that you speak to several power companies about their particular schemes. The local network operator must be notified of the installation of a Grid-connected Solar PV system.

Will Solar PV protect my house from power cuts?
Not if it is a ‘Grid-connected’ system. As a safety requirement the inverter constantly monitors the supply Grid and must shut down immediately if the power supply fails. It will automatically restart when the power supply is reinstated on the Grid. The inverter needs a 230V electrical supply to convert the DC from the Solar modules to AC. 

What happens when there is little or no sunlight, e.g. during winter months?
Solar PV modules do produce more electricity on brighter days, however sunlight is not a necessity. Even in the winter months when the sun is lower or the skies are overcast, Solar PV modules can still produce some electricity. The output will just be lower.

Do the Solar PV modules have to be installed at an angle? Can they be laid flat on a flat roof?
Solar PV modules should ideally be installed at an angle between 30^o and 45^o  to ensure they receive the maximum amount of light available throughout the year. Any module installed at an angle outside of this specification will see a reduction in module output, which would affect the overall system performance.