How to buy solar panels How does solar PV work?

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Monocrystalline solar cell

Solar photovoltaic (also known as solar PV) systems convert energy from the sun into electricity, and can save you money by harvesting this free electricity. Solar PV systems can be relatively simple, with their main components being solar panels or modules. 

Here we show you how solar PV systems work, what the different types of solar panels are and what else makes up a solar PV system.

Types of solar PV panels

Solar panels are made of a thin layer of semi-conducting material between a sheet of glass and a polymer resin. When exposed to daylight, the semi-conducting material becomes 'energised' and this produces electricity.

The are four basic types of PV panel: monocrystalline, polycrystalline (or multicrystalline), hybrid and amorphous silicon. All are made from silicon, but differ in the way the silicon is cut and treated. 

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Polycrystalline solar cell

PV panels will differ in efficiency (how much of the sun's energy is used by the system per unit area) and in price. 

  • Monocrystalline cells tend to be more efficient than polycrystalline cells (13-17% efficiency)
  • Polycrystalline cells can be cheaper than monocrystalline cells, but are a bit less efficient (11-15% efficiency)
  • Hybrid cells combine crystalline cells with another cell type, called thin film. This makes the panels even more efficient (17%+), but they cost more. 

So, when deciding which type of solar cells to go for, it's best to look at cost per watt (£/W) of power output. You can do this by dividing the total cost of the solar system you are being quoted for by the total power output of the system. 

When comparing quotes, make sure you know what type of solar PV cells you are being quoted for.

Solar panel efficiency

More efficient panels will tend to cost more. Before taking the plunge and buying more expensive panels, it's worth also taking the size of your roof into consideration. If you have enough space, cheaper, less-efficient panels could end up being more cost-effective over time. 

However, if space is limited, you would probably want to maximise efficiency to get more power out of your few panels. 

HIT hybrid solar PV cell

Hybrid solar cell

Solar panel modules and system

A solar PV system is usually made of solar panels, an inverter, isolator switches, a PV generation meter and cables.

  • The more panels you can fit on your roof, the more expensive the system will be to purchase and install, but the more electricity you will produce.
  • The electricity produced by the PV panels is direct current (DC). Before it can be used in the home it has to be converted to safer alternating current (AC), using a box called an inverter, often placed in the loft. 
  • It's worth noting that the inverter doesn't have the same lifespan as the panels themselves. If it fails, then a replacement inverter could cost at least £1,000.
  • For safety, isolator switches are also placed before and after the inverter.
  • A PV generation meter is connected inside your home, in a visible location, so you can see a real-time display of how much electricity the system is generating. The meter also measures the amount of electricity exported to the grid, and this is used to calculate your Feed-in Tariff (FIT) payment - which provides cash in return for generating your own electricity.
  • Finally, if you want to export excess electricity to the grid, there will be another cable to your consumer unit (fuse box).

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