Solar Electricity FAQs

Q: Are all solar panels the same?

A: No, some solar panels produce electricity, these are called photovoltaic (pv) panels.  Other panels heat water. These panels are known as solar thermal panels.
 

Q: Are all photovoltaic panels the same?

A: No, all panels have different performance characteristics just like cars! Panels are rated according to the power they produce under set conditions as well as how good they are at converting light energy into electrical energy – their efficiency. 
 

Q: What do photovoltaic (PV) systems consist of?

A:  PV modules (groups of PV cells),  commonly called PV panels, an inverter (to convert dc current to ac current for use in home and grid export), wiring and safety devices, a mounting  framework and monitoring devices which measure output.
 

Q: Can you put solar PV panels on any roof?

A: Solar panels can be mounted to any roof, as long as there is plenty of unshaded space. We would suggest to get the best return you put them on a South-facing roof, but they will still be effective on an East or West roof.  If you have a flat roof, we can install frames to angle the panels towards the South.  We can fit panels to any type of tile, slate, metal or felt roof.  Flat roofs and ground-mounted options are also available. 
 

Q: How does a photovoltaic system work?

A: Light hits the photovoltaic cells and is converted to clean electricity.  The inverter converts the electricity from direct to alternating current, for use in the home.  When the solar energy system is producing more power than is needed it is exported to the grid automatically.  At night, power is imported from the grid as it normally is. The connection is made at your mains board or consumer unit.
 

Q: How do you measure how much energy a system produces?

A: Solar energy (once converted into electricity) is measured in kilowatt hours. A kilowatt hour is how your energy company measures your usage at home. A kilowatt hour equates to 100 x 10watt low energy lightbulbs  being on constantly for one hour or 10 x 10watt lightbulbs being on constantly for 10 hours.
 

Q: What is the difference between a kilowatt (kW) and a kilowatt hour (kWh)?

A: A kW is a thousand watts and a unit of power.  It measures the rate of energy conversion.  A kWh is the amount of work done, or energy used, when a kW of power works for one hour.
 

Q:  What is a kWp, and how does it relate to kW and kWh?

A: A kWp is the kilowatt ‘peak’ of a system which is a standardised measure for panels across all manufacturers to ensure that performance characteristics  are capable of comparison. It is the general measure of system size.

The test conditions for module performance are rated under Standard Test Conditions (STC) : irradiance of 1000 W/m2, a module temperature at 25°C and a solar spectrum of AM 1.5. Just as no two different panels perform the same, systems which have the same kWp rating will perform differently depending on the characteristics of the panels in the system.
 

Q: Do panels require any maintenance?

A: The good news is that solar PV panels do not require very much maintenance.  They are self-cleaning, and do not require an annual service.  The inverter may require replacing at some point during the expected 25-40 year life-expectancy of the PV panels. 
 

Q: Is the UK sunny enough? What about in winter?

A: Yes. The efficiency of of solar power systems have improved so it is now a viable option even in cloudier climates.  Solar power depends on intensity of light, not necessarily direct sunlight. So even when it’s overcast, your solar panels will be producing clean electricity to help power your home. Yes the panels will produce less energy on winter days but will still work effectively.
 

Q: What happens when there is a power cut?

A: If there is a power cut your grid connected system is automatically switched off to protect  individuals working to restore the power supply. Some battery connected systems will work in a power cut, fund out more here
 

Q: Does the system need back-up batteries?

A: No, your system is connected to the national grid.  At night, when no generation is taking place, electricity is supplied by your electricity company.  Excess electricity generated during the day, for example when you are at work, is sold back to the utility company automatically.

If you would like to maximise your self-consumption or keep the lights on during a power cut, there are some great battery storage solutions which work well with solar PV systems.  You can find out more about them here
 

Q: How much energy does my property need?

A:  The average 3 bedroom house consumes 3,300 units of electricity (kWh) a year (cooking and heating using non electric supply) according to the Energy Savings Trust. To find out your yearly usage call your electricity supplier. It’s not vital that your production equals your usage. We recommend that customers get a large a system as they can afford on their roof as the incentives for production are so attractive. So it’s more of an investment decision.
 

Q: What if I produce more energy than I need?

A: When you produce more electricity than you use it will flow back into the grid for others to use.  Your energy provider is obliged by law to pay you for this if your installation has been installed by an MCS accredited company.   We help our customers with this paperwork to ensure they get the incentives they are entitled to.