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Solar panels essentials

Solar Panel Jargon

By Sarah Ingrams

Article 2 of 2

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Solar Panel Jargon

Buying solar panels can be confusing if you don't know what all the jargon means. Our solar panel jargon buster will help make sure you don't get caught out.

Thinking of getting solar panels? Then make sure you know your amorphous from your evacuated tubes. 

Once you're up to date on your solar panel jargon, find out which manufacturers make the best-quality solar panels. See our solar panel reviews.

Solar panels jargon buster


A type of of solar photovoltaic (PV) cell. Unlike multicrystalline and monocrystalline cells (see below), amorphous panels are not made from interconnected solar cells made from expensive crystalline silicon. 

Instead, a very thin layer of silicon is sprayed on to a backing material to make solar roof tiles. As the silicon is much thinner than the silicon wafers in a typical crystalline solar cell, material costs are greatly reduced.

Active solar 

Using a collector, such as a solar panel, to capture the sun's energy to heat water or convert it to electricity.

Drainback system

A type of solar water-heating system where the water inside the solar panel drains into a small back bottle when the pump switches off. This protects the system against damage caused by boiling and freezing, without the use of antifreeze.

Evacuated tubes

A type of solar water-heating panel. Evacuated glass tubes collect the sun's energy and heat water running through a container at the top of the tubes. They can also be called vacuum tubes.

Feed-in Tariff (FIT)

The FIT scheme allows you to receive payments in exchange for owning a solar PV system. It also pays you for excess electricity sold back to the National Grid. For a detailed guide to the FIT scheme, check out our dedicated guide to the Feed-in Tariff.

'Free solar' or 'rent-a-roof' schemes

Schemes where companies pay for the cost of installing and maintaining solar panels on your roof, and then generally take all of the FIT income. Householders still benefit from the electricity produced by the panels. To find out more, go to free solar panels.

Integrated solar panels

Also called ‘in-roof’ systems, these are solar PV of solar water-heating panels which are fitted as part of the roof, rather than on top of existing tiles. They’re mainly found on new-build housing but can also be retrofitted.


Kilowatt peak. The unit of measurement for the maximum amount of power your solar system can generate. On an overcast day, your system will produce less electricity than its peak power.


This refers to low-capacity electricity-generation equipment, which covers generation of electricity up to 50kW. Domestic-scale microgeneration embraces a range of technologies, including small-scale photovoltaic (PV) arrays, micro-hydro generation, small wind generators and domestic-scale Combined Heat and Power (CHP) equipment.

Microgeneration Certification Scheme (MCS)

This is a certification scheme for products and installers of microgeneration technologies, such as solar PV. You must use MCS-certified products and installers in order to qualify for the FIT and the Renewable Heat Incentive (RHI).

Monocrystalline silicon cells

The most efficient and expensive PV cell. Cut from single crystals of silicon, this system can harness around 15% of the sun's energy that shines on it.

Multicrystalline silicon cells

A PV system made from silicon cut into wafers. It's slightly less efficient than monocrystalline cells but also slightly cheaper. It’s also called polycrystalline.

Passive solar

Capturing the sun's energy without a panel or collector – for example, through large south-facing windows – and minimising heat loss through insulation.

Photovoltaic (PV)

PV cells are thin layers of semi-conducting material (usually silicon). Electrical charges are generated when the silicon is exposed to light, which can be conducted away as direct current. Multiple cells are connected together (usually behind glass) to form a panel.

Find out more about how solar PV works.

Pressurised system

Water is pumped through the solar panel and heated. This heated water flows through a heat exchanger, warming the water stored in your hot-water cylinder. These systems typically use antifreeze.

Renewable Energy Consumer Code (RECC)

This is the consumer code that installers of microgeneration technologies sign up to in order to get MCS certified. The consumer code sets out clear standards of consumer service before, during and after a contract is signed.

Renewable Heat Incentive (RHI)

A financial support scheme that is paid to householders for generating renewable heat, similar to the FIT scheme (which pays people for generating electricity). It covers technologies such as heat pumps, solar thermal and biomass boilers. You can find out more in our guide to the RHI.

Solar and storage

A home renewable-energy system made up of solar PV panels (usually) and a home battery. This enables you to store excess electricity produced by your panels during the day so you can use it at night.

Solar tiles

Solar tiles use the same technology as photovoltaic cells, but are smaller and narrower than PV panels, and look like roof tiles.

Solar water heating

Water is pumped through a solar panel and heated by solar energy. The heated water then flows through a heat exchanger, warming the water in your hot-water cylinder. Learn more about how solar water heating works.

Thermal store

They’re a way of storing excess heat generated by your renewable system, such as wood-fuelled biomass boilers, heat pumps, wind energy and solar water heating. Usually it’s a large, well-insulated cylinder containing a heat exchanger to heat up mains cold water.