Solar Tool FAQs

1.    How to use the Solar Tool

The Solar Tool is fully automatic. If your property is within the PO postcode boundary, you can just search it by entering your postcode and address. Simply enter the postcode in the “Search Postcode” box, and click “Find Address”. Then a dropdown list of all properties within the postcode will appear. Choose the property that you are interested in, and click “Evaluate” to see the result.

2.    Why can’t I find my address?

The model uses the Portsmouth address database which is updated periodically. If your property is not within the City of Portsmouth (most of the PO1 to PO6 postcodes), it is unfortunately not covered by the study area of this model. If your property is within Portsmouth, it is possible that they are not included in the database. In this case, you can contact Switched On Portsmouth by emailing, and we will arrange an individual study of the building for you.

3.    How does the Solar Tool understand my roof and it’s shape?

The tool, developed by Switched On Portsmouth’s partner Absolar, uses LiDAR data and computer simulation to identify the shape and structure of buildings within Portsmouth. The LiDAR data are able to create a high-resolution 3D model of buildings on a virtual platform, performing simulations for solar radiation and electricity production.

4.    Why does the tool only choose parts of the roof?

If the roof is composed of different sections, the tool is able to analyse the structure and geometry of each section; including orientation, inclination, and curvature. Thereby identifying the most suitable areas where solar panels can be installed. The selected areas are chosen as they meet the following criteria:

  • The area able to receive an adequate amount of solar radiation over a year
  • They have large enough surface spaces
  • The surface areas are suitable for panel installation

5.    Can I install more panels or panels on other areas not highlighted?

The tool proposes a suitable configuration of solar energy systems for your roof. It is possible that your roof can be fitted with more solar panels and still be financially feasible. You can discuss this with the installer when they perform pre-installation, on-site surveys. If you feel that your property can install significantly more panels than proposed, you can also contact our energy advisers at Switched On Portsmouth via

6.    How is the payback period calculated?

We calculate the payback period by taking into account 1) capital cost for installing solar panels, 2) potential electricity production from the proposed solar system, 3) estimated electricity demand of the property, 4) estimated electricity surplus, if any, from the solar panels and the resulted payment from energy suppliers, and 5) estimated electricity price increment.

The tool updates its economic parameters periodically to reflect the latest market values. The current parameters used by the app are as follows:

  • Electricity purchase tariff: 15 p/kWh
  • Smart export guarantee tariff: 4.0 p/kWh
  • Typical solar panel installation:
    • 1 kW: £2050
    • 2 kW: £3250
    • 3 kW: £4350
    • 4 kW: £5200
    • 5 kW: £5800
  • Annual electricity price increment: 3%

7.    How do I get more benefit from my solar PV panels?

Demand side management

Electricity production from solar panels is highly dependent on time of the day. You can increase the financial benefit by shifting the use of high-power appliances to during the day time when your solar panels are producing electricity.

Battery and energy storage

If you have a large amount of electricity surplus from your solar panels, you can also install an energy storage system, such as batteries, to help reduce surplus. Contact our adviser at Switched On Portsmouth to know more.

Export tariff

After April 2019, the UK government has changed the export tariff scheme to the Smart Export Guarantee (SEG), requiring energy suppliers to set up their own SEG tariff for solar panel owners who export electricity surplus to the grid. Currently, several energy companies have announced their own SEG tariffs, which vary significantly. You may receive a higher SEG payment by changing energy suppliers. Contact our adviser at Switched On Portsmouth to know more.

8.    Can I get financial help to install solar panels?

Visit our Solar funding to see what financial help is available at the moment. We sometimes have funding available to install Solar PV for FREE!

General PV FAQs

If you haven’t already, and are looking for some general information on Solar PV – see our Brief Guide to Solar PV.

1.    What is solar PV?

Solar photovoltaics (PV) are materials that convert light directly into electricity, using no moving parts.  It is made out of semiconducting materials, most usually silicon.

2.    What are solar PV panels made of?

The heart of the panel is made of wafers of semiconducting material, usually silicon – 95% of the market for PV is silicon panels. Other compounds such as gallium arsenide and copper indium diselenide are available. Plastic PV is just coming to the market although conversion efficiencies are still low. In future, materials called perovskites look to be a promising low-cost solar conversion technology.

Apart from the solar material itself, modules also contain a glass front surface, an aluminium frame and polymer resins to seal the panel and prevent water getting inside.

3.    Are solar PV panels safe?

If installed correctly in accordance with IET regulations the PV is perfectly safe.  The same could be said of any electrical circuit.

4.    How much energy does it take to make a solar PV panel?

An entire solar PV system including panels and inverters, will repay the energy needed to manufacture it within 3 years operating in the UK.

5.    Do solar PV panels affect the value of my house?

The value of your property is very much down to the opinion of the prospective buyer. However, solar PV will increase the energy performance rating of the property (EPC rating), and we are seeing a correlation between energy performance and house price for properties in the same location – that is to say an efficient home is seen as more desirable.

If you move out of a property that has had solar PV installed at the very least the new owner/occupier will benefit from reduced energy bills which should be seen as a plus. However the quality of the installation is also important. To give yourself the best chance of increasing the value of your property with solar it is important that you look for a reliable installer who will be available in the future to respond to any questions or issues.

6.    Do PV panels generate electricity when it is cloudy?

Yes – PV panels can use direct or indirect sunlight to generate power, although they are most effective in direct sunlight. The panels will still work even when the light is reflected or partially blocked by clouds, albeit not as productively as a clear, sunny day.

7.    Can electricity generated from PV panels be stored to use later?

In order to store electricity generated by the PV panels you would require a separate battery storage system, otherwise the electricity can be exported back to the grid at an export rate. Alternatively, you can couple the PV panels with the immersion heater on your water to produce hot water as a means of storing the energy generated.

8.    Do I need planning permission to install PV panels?

In most cases solar panels do not need planning permission, however you should check local planning policies with your local council, or speak to your specialist installer. Especially if your home is in a conservation area or is a listed building. General planning advice on solar panels is found here.

9.    What maintenance is required?

Solar PV systems are largely maintenance free. Rain should keep your panels quite clean, but dust, grime or bird droppings can impact the productivity so it is worth having them cleaned occasionally, or if you notice a fall in the production of the system. Panels are made with a special coating making them self-cleaning, if installed at a pitch above 10 degrees. If you do need to clean your panels, pick a company that is equipped to do the job safely and to a good standard.

10.    Do I need a south-facing roof for solar panels?

Solar PV panels work on any roof facing south, south-east or south-west. Although your PV panels will perform better and produce more electricity if they are south facing, they will still perform at 86% (compared to south facing) either facing east or west.

11.    What guarantees will my solar PV panels come with?

Your Solar Panels will come with a manufacturer’s guarantee of the panels’ performance. Different manufacturers offer different guarantees, with the more premium levels of protection usually associated with the more expensive panels. It’s wise to make sure you understand the guarantee before you purchase.

12.    How long will my solar PV panels last for?

Solar PV systems have no moving parts apart from the inverter and as such have very long life spans. The inverter should last for over 10 years and may cost up to £1,000 to replace, however you can buy an extended 20 year warranty for as little as £300. You should expect the panels to last for at least 25 years.

13.    Is there a risk of my solar PV panels blowing off the roof during a storm?

It’s highly unlikely, when solar PV panels are installed they are securely attached to the fabric of the building using a roof hook and rail system. Panels should always be mounted at least 30cm in from the edge of the roof to prevent excessive wind loading.

14.    How do solar PV panels connect to the electrical supply in my home?

The electricity produced by your solar panels is converted from DC (direct current) by the inverter to AC (alternating current), which your home is run on. The electricity is then taken from the inverter via an AC cable to your distribution board, where it is used to power the circuits in your home.

15.    If I have solar PV panels can I come off grid?

Solar PV panels alone will not give you electricity 24 hours a day as they only produce electricity in daylight hours. You would need alternative energy sources or a battery system as well as Solar PV panels to be able to come off grid.


If you have any further questions not covered on this page then please contact