Solar Frequently Asked Questions

12 October 2022 @ 14:17 BST by TB Electrics


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To help you understand more about how our solar installations work, here are the answers to some of the common questions we get asked.

How does Solar PV Work?

A solar PV system starts with sunlight hitting the panels on your roof or on the ground, the sunlight then causes the panels to generate electricity, this electricity is DC power. The DC power electricity then runs down the cables to an inverter where the DC power is changed to AC power that is the same as what is used in your house. At this point the AC electricity that is being produced from the panels will either be sent into the house if you are using electricity, if you are not using electricity, it will be sent back to the grid unless you have a battery connected to the inverter, in that case the electricity from the solar can be stored in the battery and used later.

Types of Solar PV Inverters?

The Inverter is the heart of the solar PV system, this is where a major part of the work takes place. There are three main types of systems for solar PV inverters.

  • String Inverter (this inverter allows you to connect solar panels and inverts power from DC to AC to use in your house, if there is no power being used in the house but the sun is out then the power will be sent back to the grid).
  • Hybrid Inverter (this inverter allows for the same as the string inverter but also allows for a battery to be connected to the inverter to store any of the power that is not being used in the house and is currently being sent to the grid).
  • OffGrid Inverter (this inverter allows the same as the hybrid inverter but does not connect to the grid at all, so you would need to wire circuits into a different consumer unit and connect that consumer direct into the inverter

How are solar panels installed on my roof?

There are different methods depending on the type of roof covering you have. Usually, panels are mounted on a rail system that is fixed to the roof.  We refer to this as ‘on-roof’. If the panels are being installed on a new property, or you are replacing the roof covering on your existing property, then the panels can be installed ‘in-roof’. This means that you can reduce the amount of tiling/slating materials required to cover the roof. All solar PV systems are designed to maintain the strength and integrity of your roof, whilst remaining watertight.

In-Roof GSE - GSE In-Roof

On-Roof - Renusol On-Roof

What if my roof doesn’t face south?

Here in the northern hemisphere, south facing roofs are generally best for solar generation, however, east and west facing roofs can yield very similar results when used in conjunction. North facing roofs can be used but we usually wouldn’t recommend this as they produce a lot less electricity. However, if your goal is to produce as much electricity as possible with the roof space that you have, a North facing array can be incorporated into a design.

Does shade affect how much electricity the panels will generate?

Yes, shade plays a big part in how effective the solar panels are. As part of our survey and design process we calculate a shading report for the solar installation. Shaded parts of the roof would result in lower yield, so we tend to avoid them where possible. However, shade in the early morning and late evening have a much lower impact on overall production than if the panels were shaded in the middle of the day so it’s important to consider all options.  There are ways to mitigate the affect that shade has on your electricity production however, such as installing optimisers to some or all the panels.

What is an MPPT?

An MPPT (Maximum Power Point Tracker) Algorithms are used to give you the best output from the panels, the MPP can vary with change in temperature and solar irradiance. With the conditions constantly changing the MPPT controls the voltage and current from the panels depending on the load connected to the inverter, ensuring the panels always work at the highest efficiency. Normal PV inverters (Hybrid or string) have 2 MPPT’s with each MPPT allowing for multiple panels to be connected to it. However, it is best to keep all the panels that are connected to one MPPT in the same orientation, since if one panel is in shade and the other is in sunlight both panels will be reduced to the shaded panels power. With the inverters having two MPPTs this allows you to have two roof orientations with panels on if required. If you have more than two roofs you would like panels on, then you may need optimisers.

What are Optimisers and do they help with shade?

Optimisers are small devices that are fitted to each individual panel in order to improve the performance of the overall system. They work by monitoring each panel and adjusting the voltage to maximise its power output. They are often recommended for shaded roofs as they can help minimise the effect that shaded panels have on the overall system. They are also recommended for roofs that have multiple orientations as they can help balance the system better when panels are facing in different directions.

For a more detailed explanation of how optimisers work, Click Here.

How long do solar panels last? Do they get less efficient over time?

Most panels come with a 25-year performance guarantee which is based on panel efficiency dropping by approximately 0.8% each year, however some of the premium panels, such as Sunpower reduce the expected degeneration down to just 0.2% - allowing you to produce more energy for longer.

Do solar panels work in a power cut?

By default, all solar installations are designed to automatically switch off when they detect a grid power cuts.

This is to protect the engineers that might be working on the grid as there is a high risk of electrocution from the electricity your panels would be producing.

Solar installations can be designed to work during a power cut by disconnecting or ‘islanding’ your property from the grid when the system detects a power cut. A battery can also power small circuits in your home if there is a power cut – keeping things like your lighting, TV Broadband or fridges etc running if you have a power outage.  If this is something you would like to consider for your installation, please let us know and we can provide you with more information depending on the inverter being used.

Do I need a battery with my solar panels?

In most cases, domestic solar installations benefit from having a battery installed. Having a battery allows you to use the solar electricity you generate at the times that suit you, not just when the sun is shining. The size of the battery we recommend would depend on how much electricity the panels can generate and also how much you are likely to use.  

Do solar panels need any maintenance?

Panels don’t need any mechanical maintenance as they have no moving parts. We would recommend occasionally cleaning to keep your panels running optimally as dust and other debris can gradually build up over time reducing the amount of daylight hitting the panels.

As solar panels are mostly glass, they can be treated much like a window and cleaned with water and soft brush.

Cleaning once a year would usually be more than enough to keep panels working optimally, it would depend on factors such as the amount dust, birds, leaves etc but you might find that the rain does a lot of the cleaning for you.

Can I get paid for the electricity I export?

Any electricity that is generated but not used either in the house or stored in a battery is automatically fed back to the grid. The good news is you can get paid for the electricity you export.

 The current method of getting paid for the electricity you export is the Smart Export Guarantee or SEG. This replaced the older Feed In Tariff (FIT), which is no longer available.

TB Electrics are part of the Microgeneration Certification Scheme (MCS). This means your installation will meet the requirements needed to apply for an SEG tariff

Normally when applying for an export tariff or SEG, the energy supplier will request the following documents:

  • Your MCS Certificate
  • DNO approval (also known as a G98 or G99 depending on the size of your system)
  • Proof of purchase of your solar installation.

You will also need to have a smart meter to allow the company to monitor how much electricity you are exporting. If you do not already have a smart meter, please contact your energy supplier and they should fit one free of charge.

Do I need planning permission for solar panels?

Solar panels are known as a "permitted development". This means that for most domestic properties, planning permission is not required.

There are, however, some conditions that solar installations must comply with:

  • The system should be installed in such a way that the effect on the external appearance of the building and the amenity of the area is minimal.
  • When no longer needed, equipment should be removed as soon as reasonably practicable.
  • The system cannot be higher than the highest part of the roof (excluding any chimney).
  • The system cannot protrude more than 0.2 meters beyond the plane of the roof slope.

When is planning permission required?

  • On flat roofs. This is because solar panels on a flat roof are usually placed in frames to create an angle towards the sun. This means they typically need to protrude more than 0.2 meters above the roof slope which is contrary to the "permitted development" guidelines.
  • Listed Buildings/Scheduled monument. In these circumstances you would require listed building consent followed by planning permission.
  • Conservation areas. It is possible to have solar panels installed but there are specific limitations to take into consideration. Each planning authority will have its own rules around this, so it is advised to look at your local council’s website.
  • Ground Mounted. A small system can be installed without planning permission, but in most cases an application will need to be made.

What is DNO and how does it affect me?

DNO stands for ‘Distribution Network Operator’. The DNO are responsible for the electricity supply in the area you live in. All powerlines, underground cables etc that get electricity to your home belong to them therefore upon requesting approval we require this from the DNO and not necessarily your current electricity supplier. We will submit the DNO application on your behalf if you require one before your install. It can take up to 45 working days for them to respond to us however it doesn’t usually take this long. If there is a charge payable to the DNO the invoice will be invoiced directly to the customer to make payment to them as we do not include this charge within our quote as there may not be a charge from them and if there is the price can vary.

What is covered by the guarantees/warrantees?

Most products have their own manufacturing warranties. Usually, they have a minimum of a 5-year warranty which can be extended however each brand does vary. TB Electrics offer a 10-year workmanship guarantee on all our installations.

How do we pay for our install?

Our preferred method of payment is BACS however we can take card payment over the phone. We usually have a 3-stage payment plan that will be given to you in your contract documents. We request a deposit upon you agreeing to go ahead, then 50% of the remainder once we have booked you in for your install & the remainder once the installation is complete.

When will we receive our handover pack & what is included?

Your handover pack will be issued within 3 weeks of full payment being received. This will include all documentation for your install & all documents that will enable you to get SEG Payments.

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