FAQ Solar Electric (Photovoltaic)
How much power do we use in our home?
Everyone consumes energy, but sometimes it is hard to know just how much power is really being used in the home. Domestic energy usage is measured in kilowatt hours (KWH) and the best way to understand what this means is to look at what a KWH does in every day life. A KWH of electricity can provide:
1200 electric shaves
Drying your hair 15 times
Listening to 15 CD'S
Using a small refrigerator for 24 hours
Microwaving 20 meals
4 evenings of light with 60W incandescent lamps
An average 3 bedroom house uses between 9-10KWH per day
What is a Solar Photovoltaic (PV) system?
A Solar Photovoltaic system (or Solar PV as it is commonly known) is a renewable technology which utilises free energy from the sun to generate electricity. The electricity produced by Solar PV can be used to drive anything from an appliance to a light bulb that is usually powered by the mains electrical supply.
How does Solar PV work?
Solar PV relies on daylight to generate power through the use of photovoltaic cells within roof mounted panels(modules). These modules are generally fixed to a roof and connected by cables into an inverter. This converts the DC electricity produced by the modules to AC (the same as the electricity that comes from the National Grid) which is either consumed within the property or sold back to the power supplier.
What is the difference between Solar PV and Solar Thermal?
As previously mentioned, 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.
What happens when the weather is cloudy or cold?
Solar PV panels use light to generate electricity, so the modules still work when it is cloudy, although when it is overcast they are less efficient. When it is slightly overcast, the panels may produce as much as half the power they would in sunny conditions. When the sky is heavily overcast, this could reduce further. Temperature is less important than how much light there is. What’s more, a clear cold day is perfect, because pv modules operate better at cooler temperatures. Where did the idea of PV come from?
Where Did PV come from?
In 1839, a French scientist named Edmund Bacquerel discoved the photovoltaic principle and the first basic solar cell was developed some 40 years later. However, today’s photovoltaic technologies were developed in the 1950s and 1960s for uses including satellites, spacecrafts, electronic watches and calculators. The idea behind the domestic use of PV to provide renewable power for the home, has now been established for over 20 years.
What are the key benefits of Solar PV?
A Solar PV system has many unique features. It is available in simple kit form ranging from 0.4kW (two modules) to 1000000kW , making it limitless. Bespoke systems of almost any size can also be designed and supplied using the same basic components found in the kits.The systems utilise MCS Accredited 200 Watt monocrystalline Solar PV modules. The module frames are made from corrosion-proof, anodised aluminium and meet the highest requirements in terms of stability and durability.
What is the difference between polycrystalline and monocrystalline modules?
The polycrystalline modules use cells made from a multi crystalline silicon material with a blue marbled appearance.The monocrystalline modules have cells of a darker appearance, almost black in colour. These are produced from a pure single crystal silicon, resulting in a cell which is slightly higher in efficiency than the multi crystalline silicon cell. Thus the monocrystalline modules are typically smaller in physical size than a polycrystalline one of the same output.
What mounting options are available for Solar PV?
There are several different mounting arrangements available including on-roof, in-roof and flat-roof (by special order),with both landscape and portrait module installations possible.
What is the life expectancy of a PV Module?
PV modules have a life span of over 25 years, but should last much longer since there are no moving parts.
How long is a PV system guaranteed for?
PV Systems are covered by a unique five-year manufacturer’s and company guarantee, subject to the system and its components e.g. inverter, modules, etc. being supplied and fitted by us. Solar PV modules also carry up to a 25-year performance guarantee as follows: Performance guarantee to 90% output minimum after 12 years. Performance guarantee to 80% output minimum after 25 years.
How many Solar PV modules are needed to produce a kW of electricity?
Solar PV modules will produce a maximum output of 200 watts each in bright sunlight (warranted under standard test conditions ‘STC’). This is written as 200Wp (watts peak). For example, if six modules are connected together they will produce 6 x 200 =12000 Wp or 1.2kWp (kilowatts peak).
What size PV System do I need?
Electricity requirements vary depending on the size of your house and how energy-efficient the building and appliances are. A standard three-bedroom house consumes approximately 3300 kWh of electricity per annum, excluding heating and cooking (Source: Energy Savings Trust).To put this into perspective, a 2.88kW Solar PV System (approximately 16 panels) should produce around 3,285kWh of electricity per annum. For a more accurate calculation of your household electricity consumption, either check with your energy supplier or refer to previous electricity bills.
How is the electricity produced by a Solar PV system connected to the electrical system in my house?
The DC power produced by the solar PV modules is converted to AC by an inverter and this is connected to the electrical system of the property, usually via a 16A circuit breaker in the consumer unit.
I have heard a system can be installed as an ‘off-grid’ arrangement. What does this mean?
If you live in a situation where there is no electricity or connecting to the Grid is not possible, an ‘off-grid’ solar PV system (commonly referred to as an ‘island system’) could be installed. This system incorporates a number of batteries charged from the DC output of the PV modules, so that any excess power is stored for times of no solar gain. An inverter is then used to convert the DC power from the batteries into AC, to supply the electrical system/appliances.
Do I always need to store the electricity generated in batteries?
Batteries are not a used if the system is ‘grid connected’, that is to say it is connected to the electrical supply network,via the electrical system in the property.
What happens to the electricity produced by solar modules that is not used in my house?
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.
How can the amount of electricity generated by a Solar PV system be checked?
An ‘export’ meter installed between the inverter and consumer unit, will record the power supplied by the Solar PV installation.
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 Tariffs (FiT)?
On 1st February 2010, the Government announced new standard generation Feed-in Tariffs (FiT) rates due to start on On 1st February 2010, the Government announced new standard generation Feed-in Tariffs (FiT). This started on the 1st April 2010 and is 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 2012 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 = 53.3pper 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?
Yes, it is recommended that you contact your energy supplier before you purchase and install a Solar PV system, as 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.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.
What is the minimum number of Solar PV modules that can be installed?
The minimum number of Solar PV modules that can be installed is ‘one’.
What is the maximum number of Solar PV modules that can be installed?
There is no maximum number of Solar PV modules that can be installed in a system, however, in very large installations, modules will be split into groups (known as ‘strings’). Each of these strings will then be connected to its own inverter. The more strings made, the more inverters needed. The number of modules in a string will vary depending on the type of inverter used.
How long does a Solar PV system take to install?
This varies depending on the size of system. A standard domestic grid-connected 2.5kWp Solar PV system should only take a few days to install.
Can I increase the size of my Solar PV system in the future by adding additional solar module?
Yes, it is possible to do this, providing there is sufficient roof space with the correct orientation and the maximum input to the inverter is not exceeded if more modules are connected to it. Lee Costello will be able to advise you of this.
Do the PV modules have to be installed at an angle? Can they be laid flat?
A PV module should be fitted at an angle of between 30 and 45 degrees to ensure they receive the maximum amount of light available any module fitted outside this angle would see a reduction in module output and affect the performance of the system.
Can Solar PV modules be fitted on a roof facing in any direction?
Ideally Solar PV modules should face South to achieve the maximum power output. Modules facing South East or Southwest will produce a slightly reduced amount of power.
Will planning permission be required to install Solar PV modules on the roof of my house?
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 effect of wind pressure and roof loading we can always arrange and recommend a structural engineer.'
How much will a Solar PV System cost?
For a Grid-connected Solar PV system, has a range of standard on-roof kits starting from the smallest 0.54kWppack up to 4.00kWp. Larger bespoke on-roof, in-roof and flat roof kits are available by special order and prices will vary depending on components.Typically, a 0.54kWp system would cost around £3000 to purchase, including three modules, an on-roof mounting system to suit, inverter, DC isolator, 32A AC isolator, cables and connectors.
What maintenance is required for a Solar PV system?
If the Solar PV system is Grid-connected, it will need very little maintenance. An annual visual inspection should be carried out which usually includes checks such as ensuring the modules are not in shade (by any surrounding growing trees) and in a clean condition (no routine cleaning is required as normal dirt build up is removed by rain).It is however, still recommended that a qualified electrician checks the wiring and system components within a 10 year period, in accordance with the current IE Wiring Regulations, 17th Edition Lee Costello Electrical can carry out this annual check, if required.
Is Solar PV MCS approved?
Yes, the Solar PV modules we sell are listed on the MCS Approved Register and Lee Costello Electrical is an MCS approved installer, householders will be able to access the Government Feed-In Tariffs (FiT) introduced on 1st April 2010.For approval numbers, please visit the MCS website:-
