Solar Photovoltaic (PV) vs Solar Thermal (2026)

Written-by

Janet Richardson

Reviewed-by

Richard Burdett

Updated on

Jan 03, 2026

Solar Photovoltaic (PV) vs Solar Thermal (2026)

Solar thermal and solar PV are two very different forms of technology designed for specific tasks. They both harness the sun’s energy for use in your home or business but fulfil different functions. In short, solar PV provides electricity and solar thermal generates heat for use in the home, most typically for hot water. Solar thermal is most commonly used to heat hot water for use in showers and hot taps rather than space heating. Thermal energy is captured by the panel/collectors fitted to your roof. A heat-conducting liquid, usually a mixture of water and glycol flows through tubes within the panel and absorbs solar radiation produced by the sun. The heat generated by this process is then transferred to the water in your cylinder ready for use. Solar photovoltaic panels collect energy from the sun using silicone cells and directly convert this energy through an inverter to usable electricity to power your appliances. 

To decide on which is the best option for your home you will need to weigh up the main differences between each technology and look at the benefits of each. 

How do Solar Thermal Panels Work?

As previously explained solar thermal panels capture energy from the sun and repurpose it to generate hot water. For your solar thermal panels to be effective they should be installed with a southerly aspect. The panels should still work reasonably well anywhere south of East and West though north-facing isn’t worthwhile at all. More often than not the panels are installed on pitched roofs, but they can also be fitted to flat roofs or ground mounted. On the whole, they can be installed under permitted development without the need to apply for full planning permission. 

Most solar thermal systems are indirect. Solar energy is trapped within the panels and transferred into a glycol-based heat transfer fluid with antifreeze, contained within a closed-loop circuit. This is then fed into a dedicated coil inside your home’s cylinder and from here the heat produced is transferred into your hot water supply. This means that the collector fluid never mixes with the output that goes to your taps. 

A closed-loop arrangement needs a twin-coil hot water cylinder, where the secondary coil runs off a boiler, air or ground source heat pump, or other source. There’s often an electric immersion backup fitted, but this should not need to be used if the controls are set effectively.

The key parts of a solar water heater are the collectors (the panels), a twin coil hot water cylinder, and a controller. 

There are two main types of solar thermal collectors most commonly used, the flat plate and the evacuated tube. The flat plate version normally has a Perspex cover mounted over an absorptive panel, through which the collection fluid is pumped. The whole unit is insulated below and at the sides.
The Evacuated tube collector is made up of one tube contained within another, with a vacuum between the two. The vacuum lets the radiation from the sun pass through to the inner tube, containing the collection fluid, while reducing heat loss. 

Flat plate thermal collectors are better than evacuated tubes in snowy conditions, simply because the snow just slides off the flat plate as it warms, whereas evacuated tubes have a vacuum insulation system installed to reduce heat loss. Solar thermal panels are unlikely to freeze in winter as they have an indirect or closed-loop system that pumps antifreeze through the collector.

Twin-Coil Hot Water Cylinders

In a solar thermal system, the hot water cylinder has two sources of heat, the solar coil and the boiler coil which is why it is known as the twin-coil hot water cylinder. Because heat rises, the base of the hot water cylinder is normally cooler than the top. For this reason, the solar coil is located near the base of the tank where it is usually cooler, to make the most of whatever solar resource is available. 

What are the Advantages of Solar Thermal?

There are quite a few advantages to using solar thermal technology, and you can find the main ones in this list:

• Solar thermal technology is more space efficient than its solar PV counterpart. So, it takes up less space on your roof
• Solar thermal also tends to be up to 70% more efficient than solar PV when it comes to collecting energy from the sun’s rays and converting it into heat. At the current time, solar PV can only convert 25% of the incoming light into electricity
• The technology is a lot less complex than solar PV
• It makes the ideal environmentally friendly solution for heating water
• They can be a valuable asset for businesses as they save a lot on energy bills

What are the Disadvantages of Solar Thermal?

There are also some disadvantages to this technology, and they can be found in the list below:

• It is less effective in the winter months when the sunlight tends to be weaker and the weather cloudier. This is because solar PV reacts to any light during the day, even if the sun is hidden behind clouds, while solar thermal relies on sunlight to heat the water in the collector, so reduced sunlight in winter means less heat generated by the collector
• If solar thermal is used to heat water which is its usual function, then part of the solar thermal system will occupy some space in the building whereas very little interior space is required by a solar PV system. Solar PV will need more space if you wish to install a solar battery with your system. Very occasionally solar thermal panels will be used for heating the home, in which case very little interior space is required
• Solar PV systems tend to be a lot more versatile than the solar thermal ones
• Solar thermal technology has a shorter lifespan than solar PV and can be more complicated. The reason for this is that while solar PV just absorbs light and then turns it into energy, solar thermal systems absorb light, turn that light into energy, and then use that energy to heat building space or water. There is more going on with a solar thermal system as it is a three-fold process as opposed to a solar PV system which is a two-fold process. This means that a solar thermal system can potentially be more complex and incur more costs
• Solar thermal systems require more maintenance than solar PV systems. 
• Finding the right supplier can be an incredibly time-consuming process

Solar thermal may be the renewable energy solution for you though currently it is almost entirely only used for heating water. 

Solar Thermal Costs and Savings 

Solar thermal systems are cheaper than PV panels, with installation costs typically ranging from £3,000 to £6,000. Because they are cheaper to install, they will often pay for themselves faster than PV panels. They can still work in cooler or overcast weather and strong winds. 

Solar thermal systems will normally provide all, or most of the domestic hot water you need during the summer as well as make a significant difference during the rest of the year. Overall, they can provide 60% of your domestic hot water needs. This can cut total energy costs by approximately 10-20% with savings increasing as energy prices rise. 

Solar thermal used to be much cheaper than solar PV. Over the past decade, however, the cost of PV has dropped by more than 50% due to funding, mass production and innovations. This means the cost differential per system is not as much a consideration as it was in previous years. 

How does Solar PV Work?

When compared to solar thermal technology, solar PV is a much newer technology. There are three main types of solar PV technology available. These are:

Monocrystalline (most efficient and most expensive)

Monocrystalline solar panels are the most commonly used for homes and the most efficient. They’re easily identified by their uniformly dark colour and rounded edges.
A mono solar cell is a single crystal of pure refined silicon that can absorb more sunlight than polycrystalline panels or thin-film solar panels. Monocrystalline panels can be designed to be even more energy efficient, with PERC (passivated emitter and rear contact) technology. 

Polycrystalline (mid-efficiency and mid-price)

Polycrystalline solar panels also known as poly panels or multi-crystalline panels have a blue hue and straight edges. They consist of multiple silicon crystal fragments bonded together during manufacture. 
Because they are less efficient than monocrystalline cells, a polycrystalline solar system requires more panels to reach the same power output.

Thin film solar cells (lowest efficiency and lowest priced. Also, most flexible)

Thin-film solar cells which are part of the second generation of solar power technology are comprised of layers of semiconducting materials placed on a glass, plastic, or metal substrate.

Thin-film solar panels are lighter and more flexible than other types of solar panels, which gives them a unique advantage. However, thin-film solar cells are generally less efficient, as they require a larger roof space to generate the same amount of energy. 

Solar photovoltaic (PV) panels use cells that contain a semiconductor material, most commonly silicon, to capture the sun’s energy and convert solar radiation into electricity. A certain amount of energy is absorbed within the semiconductor material when light strikes the cell which knocks electrons loose. Electrons are the negatively charged particles that form the basis of electricity. 

Most PV cells have two layers of semiconductor material, one positively charged and, one negatively charged. When light shines on the semiconductor the electric field across the junction between these two layers causes electricity to flow, generating direct current (DC). Metal contacts placed on the top and bottom of the PV cell then draw that current off for external use. This direct current (DC) needs to be converted into alternating current so it can be used for your domestic appliances for example. This is achieved with the use of an inverter. The alternating current (AC) electricity then passes via the generation meter, which measures how much electricity has been created, and on to the consumer unit where it can be fed into the property for use or exported back to the national grid via the electricity meter.

What are the Advantages of Solar PV?

There are several advantages to using solar PV panels in your home. Some of the main ones are listed here:

• They can provide you with clean, green, energy for up to 50 years
• They have an incredibly long lifespan, especially when compared to solar thermal technology. They can potentially generate electricity for around 30 years. Many, solar PV systems can last for much longer, though their efficiency gradually declines over the years
• They can cover up to 70% of your household’s energy needs. Solar PV can produce more electricity than is required, especially during the summer, so the excess electricity can be exported to the Grid in return for payment
• They are incredibly efficient in the summer
• They won’t freeze over during the winter months
• They can cover the energy requirements of appliances that have a high energy consumption. This includes the refrigerator, tumble dryer, and washing machine among others
• The Smart Export Guarantee (SEG) will pay you a tariff for the electricity you send back to your provider. Payment used to come from the government under the feed-in-tariff scheme but under the SEG it is paid by energy suppliers instead. Solar PV can be used to generate an income 
• Solar PV is more flexible than solar thermal because the power generated by solar PV panels can be put to various uses

What are the Disadvantages of Solar PV?

It is an impressive technology and one that could really benefit your home. However, there are some disadvantages. Take a look below:

• The initial costs are quite large. The upfront costs of solar PV panels are typically higher than a solar thermal system. However, savings on energy bills subsequently balance this out
• They require a lot more space for installation than solar thermal energy. This can be a problem for some roofs and homes
• Finding the right supplier can be a time-consuming task. It’s a good idea to use a comparison website to find the best deal for you and to get recommendations for reliable installers
• They can diminish the aesthetic quality of a home
• If the electricity generated by your solar PV system isn’t used straight away it needs to be either stored in an energy storage system like solar batteries to be used as and when required or sold to your energy supplier which is currently a less valuable choice

As with solar thermal, investing in solar PV is a great choice. It will allow you to benefit from, and enjoy, a superior form of green energy. Solar panels will help to cut your energy bills significantly, and you will also be able to earn money by selling any excess energy to the National Grid via your energy supplier.

Solar PV Costs and Savings

The cost of installing a 4kW solar photovoltaic system on an average house is between £4,000 and £7,000. 

Typically, solar PV panels can cut energy bills by up to 70%. With a solar battery system that figure could rise to as much as 90%, with sufficient solar energy to eliminate reliance on the grid during the summer.

Savings will increase further if you sell excess solar-generated electricity back to the National Grid through the Smart Export Guarantee.

Which is Better: Solar Thermal or Solar PV?

Both solar thermal and solar PV technology are great forms of green energy and can provide you with a fantastic environmentally friendly solution. Of course, choosing between the two can be a difficult process. 

If you want something that can heat your water, however, you should invest in solar thermal technology. Something else to consider is the fact that solar thermal systems, especially in the UK climate, won’t produce all the hot water requirements for a property, especially in winter months.

A better investment would be a Thermodynamic hot water system if you wish to generate all your hot water requirements from a solar-assisted heat pump.

If you want to earn an income from your solar panels then solar PV systems are your best option because you'll receive SEG (smart export guarantee) payments for exporting excess energy to the Grid. However, this is not as lucrative an option as it once was as the tariffs offered have been greatly reduced. There is no doubt that solar PV will reduce your electricity bills though if you are seeking to reduce your heating (or possibly electric) bill then solar thermal is the best option. Solar thermal technology can be particularly beneficial for larger homes, particularly those on mains gas.  Another option is to install both solar thermal and solar PV panels. Combining the two could come at a considerable upfront cost but the savings on energy and heat/water bills could also be considerable.

Hybrid solar panels, also known as solar PVT (photovoltaic thermal), offer both systems in one but this option can have its limitations.

Using Solar PV for Water Heating

Solar PV can also be used for water heating. You can install a device called a solar PV or immersion optimiser which can detect when excess solar generation is being sent to the grid and instead divert this into heating your water tank. These devices are great because they make the most of the electricity being used on site and heat your water during the day for when you need it later. One good example of one of these is called an Eddi.

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