Solar panels: your questions answered

Solar-panel technology continues to evolve. Here are some of the most common questions we’re regularly asked, along with our answers.

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It used to be so simple, didn’t it? Make fire. Heat cave. Cook food.


We’ve come a long way since then … or have we?


Just as our ancestors worshipped various sun gods, so we are becoming a nation of sun-worshippers, harnessing the power of Planet Earth’s own personal star. We have developed cutting-edge technologies to turn sunlight into energy – to heat our caves, cook our food, and more.


Solar-panel technology continues to evolve. Here are some of the most common questions we’re regularly asked, along with our answers.


What’s the difference between photovoltaic and solar-thermal panels?


Photovoltaic solar panels (solar PVs) generate power; solar-thermal panels heat water.


Solar-thermal panels are the preferable solution if all you’re looking to do is heat your home and provide hot water for baths, showers and so on. In comparative terms they’re cheaper, simpler and longer-lasting (although you’ll need to boost the heat they provide with a boiler or immersion heater, especially during the winter).


Solar PVs convert light into energy. They function best in prolonged bright sunshine, but they will generate some power as long as they are in daylight. You can use the energy they produce to heat your home, and power your lights, your TV … all the things for which you previously depended on your electricity supplier.



How does solar PV work?


Solar PV uses the photovoltaic effect to generate electricity. When a photon (the basic unit of light) impacts on a semiconductor, an electron is released, producing a direct current. These semiconductors are formed into thin layers that constitute the core element of solar cells. The cells form the basic elements of a solar PV system. Individual solar cells are grouped together into panels, producing electrons on a larger scale. Solar panels are grouped in turn into what’s known as an array – typically ten or so panels – which is then positioned on a south-facing roof for maximum potential sunshine exposure. The power generated by the panels is fed through an inverter to convert the current from DC to AC, making it suitable to use for your domestic electricity supply.



Do I need a battery to make savings using solar power?


Strictly speaking you don’t, but to maximise your savings we would certainly advise incorporating a battery into your setup. The output from solar PVs will vary from day to day and season to season. In high summer you may end up with a surfeit of energy you can’t use, while in winter your system may struggle to produce enough. A battery-storage facility will help to flatten the day-to-day peaks and troughs, storing the excess electricity produced in times of plenty to use when daylight is in short supply.



How long does installation take?


Some providers promise to complete your installation in a day, but in our experience you need to allow two days. This includes the construction and dismantling of the scaffolding needed to access the roof area. At any point before the installation, or up to 28 days afterwards, you will need to notify your Distribution Network Operator (DNO), especially if your new equipment is connected to the National Grid. Your solar PV provider will usually do this for you. Once the panels are installed, safety tested and certified, you’re good to go!



Can I get a grant?


There are some grants available to make solar panels more affordable, but in our experience grants and low-interest loans can be offered and withdrawn seemingly at random. Where you live and how much grant money your local authority currently has in its coffers can influence your eligibility for financial assistance.


The nationwide Energy Company Obligation Scheme (ECO4) has made £4bn available in solar-panel grants. The ‘LA Flex’ element of the scheme allows local councils to decide who in their region will be eligible for the grants, so it is worth checking with your local authority to see whether you can apply for support.


The good news is that until the end of March 2027, solar panels are VAT-exempt.



Can I put solar panels on an old house?


Yes – although if your roof needs to be replaced or repaired, we advise you to have this done before installing solar panels.


There are, however, two exceptions. If you live in a conservation area you will need to obtain planning permission. If your home is a listed building, you need to obtain Listed Building Consent as well. Consent or permission is normally dependent on the placement of your array, the features of your home mentioned in any listing, and the current condition of the building.



How long do panels last?


Nobody really knows. Domestic systems haven’t been around long enough to collect any meaningful data. As a guide, most solar PVs are guaranteed for between 20 and 25 years. The US Office of Energy Efficiency and Renewable Energy currently estimates the operational lifespan of a PV module to be about 30 to 35 years. Some wild-eyed optimists reckon next-generation solar PVs could be good for up to half a century, but in our view the US figures are probably about right.



Contact us


We hope this answers at least some of your solar-panel questions. If you have more, or you’d like to discuss how solar PVs might benefit you, our experienced, qualified engineers can help. To book an appointment or request a visit, call us today on 01508 488007 or email

Excel Electrical – the power is in your hands.




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