House Design

Solar panels: a complete guide

Find out about the different solar panels – available and how they can save you energy as well as cash

Solar panels
(Image credit: Vivint Solar/Unsplash)

Solar panels are an eco-friendly way to heat the water for your home, generate electricity, or even do both from one module in the case of hybrid designs. Fit them and you’ll be using renewable energy rather than precious fossil fuels, and saving money.

See: Eco home improvements: how to make your house greener

‘The solar resource of the United States is enormous,’ says Energy Saver, an office of the US Department of Energy that provides energy efficiency and renewable energy information. ‘In fact, just one hour of noontime summer sun is equal to the annual US electricity demand. Most states in the United States have good-to-excellent solar resource.’

But what are the choices when it comes to solar panels? Our guide has all you need to know about the different options, and how they could be suited to your home. Read on to get the lowdown on solar water heating, photovoltaics, and the hybrid photovoltaic thermal panels.

April 2021 is our Green Homes month. Throughout this month and beyond, we will be highlighting the changes you can make to your home to make them more sustainable – from big projects, such as heating and cooling, to small changes, like buying sustainable homewares.

Find more eco guides on our dedicated page.

Types of solar panels 

There are two main types of solar panels which are suited for different purposes, plus there are hybrid versions that combine the functions of the main types in one panel. This is what you need to know. 

  • See: The world's most beautiful eco houses – from forest dwellings to city homes

Solar thermal panels 

Solar panels

(Image credit: Vivint Solar/Unsplash)

Solar thermal panels allow you to make hot water for your home with energy from the sun. It’s actually an older technology than solar photovoltaic (PV), see below, and an efficient one – at around 80% efficiency. A solar water heater (or solar domestic hot water system) includes the solar thermal panels themselves (the solar collectors), plus a storage tank. 

How does a solar thermal panel work? As sunlight passes through a panel and is refracted by the glass its wavelength changes, which produces heat. The heat is captured by a fluid and moved to the hot water cylinder. 

In the US, solar water heating systems may be active or passive. Active systems have circulating pumps and controls and they divide further into direct and indirect circulation systems.

In a direct circulation system household water is pumped through the solar panels and into the home. These are best if you live somewhere where it freezes rarely. In an indirect circulation system there is a closed loop of heat-transfer fluid which contains anti-freeze between the panels and the storage cylinder. The fluid doesn’t reach the faucets. A pump circulates the fluid to heat the water to use in your home. This type of system is favored in climates that experience freezing temperatures, including in the UK.

There are also passive solar water heating systems. These will likely cost less to install but they aren’t as efficient as active systems. 

The solar panels used for solar thermal systems can be of different types. Flat plate panels or collectors feature a series of pipes with a metal absorber plate on top that collects the heat from the sun, which is then carried by the fluid in the pipes to the storage cylinder. Evacuated tube panels are made with glass tubes with a metal tube inside, and they’re connected with a header pipe to form a panel. These have the edge over flat panel collectors when it comes to efficiency.

But what happens on a cloudy day? ‘Solar panels will still work in diffused sunlight, though obviously it’s not as effective as direct sunlight,’ says Martyn Bridges, Director of Technical Communication and Product Management at Worcester Bosch. ‘Nevertheless, they will contribute some heat to the hot water storage cylinder.’

In the UK solar panels can, on average, provide around 55% of annual hot water requirements of a home. ‘You will always need some other form of heating the hot water cylinder to either raise the temperature in the cylinder to the required 60ºC or for heating the cylinder when the panels are in either semi or full darkness,’ explains Martyn Bridges. ‘The most common option is usually a boiler, which is needed to heat the home anyway. Alternatively, an electric immersion heater.’

Solar photovoltaic panels

Solar panels

(Image credit: Vivint Solar/Unsplash)

Solar photovoltaic panels allow you to generate electricity from the sun. The panels contain silicon cells that create an electric current when they’re hit by sunlight. An inverter is also required to convert the direct current to alternating current for use in a home. 

You may want to invest in a battery to store the energy, too. It can be charged when the power’s available ready for use when needed. 

‘The decision to add a battery storage system depends on how much electricity you’re generating,’ explains Christian Engelke, Technical Director at Viessmann. ‘Typically, solar systems have been designed up to the maximum allowed under certain government grant programmes, such as the domestic renewable heat incentive in the case of the UK. This creates over production, with energy sent back to the grid. It can pay the homeowner to save the energy produced for use overnight, however, it needs to be calculated based on the expected usage and export. The cost of storage in the UK often doesn’t cover the difference.’

Solar PV panels can work whatever the climate where you live, but the roof of your home does need to be suitable. Its size, orientation, slope and shape as well as whether it’s shaded by trees or neighboring buildings are all crucial factors. Of course, it will also need to be structurally sound and not in need of replacement in the near future. 

If you want to check out whether your roof is suitable, you can use a mapping service via Energy Saver. You can also take a look at how much power you could generate with the tool PVWatts

Solar hybrid panels

Solar panels

(Image credit: Vivint Solar/Unsplash)

Hybrid solar panels, otherwise called PVT solar panels, are a combination of solar photovoltaic panel and solar thermal panel in one. In essence, one of these is a solar PV panel that also has pipes built into the collector with fluid circulating between it and a water cylinder. As the sun shines, its light is absorbed by the PV cells, while the heat is absorbed by solar thermal part. 

The result is that these can generate electricity and heat at the same time but, although they have the advantage of doing both jobs, these hybrid panels do have limitations when set against the separate panel types. The thermal element doesn’t reach the same high temperature as a dedicated solar thermal panel. Additional heating will therefore be required.

PVT panels can also be expensive and harder to source.

Sarah Warwick

Sarah is a freelance journalist and editor writing for websites, national newspapers, and magazines. She’s spent most of her journalistic career specialising in homes – long enough to see fridges become smart,
decorating fashions embrace both minimalism and maximalism, and interiors that blur the indoor/outdoor link become a must-have. She loves testing the latest home appliances, revealing the trends in
furnishings and fittings for every room, and investigating the benefits, costs and practicalities of home improvement. It's no big surprise that she likes to put what she writes about into practice, and is a serial house revamper. For Realhomes.com, Sarah reviews coffee machines and vacuum cleaners, taking them through their paces at home to give us an honest, real life review and comparison of every model.