Solar Thermal

The Complete Guide to Solar Water Heating

solar thermal panels

Solar thermal panels for heating water are quickly becoming a popular addition to homes and businesses across the world. A big driving force for this is their environmental and money-saving benefits, especially with heating and electricity bills consistently increasing.

Before diving into our complete guide to solar thermal panels, we should first lay out the difference between solar PV panels and solar thermal panels:

  • Solar PV panels are used to generate electricity from the sun’s energy. These systems have a solar panel inverter that converts Direct Current (DC) from the solar panels into Alternating Current (AC) that can be used in your home or business.
  • Solar thermal panels, meanwhile, generate heating and hot water from energy from the sun. These are the panels you’ll need for solar water heating.

There’s a lot to consider before investing in solar panels, so to help you out, we’ve put together this handy guide with all the information you will need to know first. Let’s dive in!

How do solar thermal panels work

Solar thermal panels, also known as solar hot water systems, utilise sunlight to heat water or transfer heat to a building’s heating system, such as radiators or underfloor heating. The process involves a few key components:

  • Solar collectors – The solar thermal panels on the roof consist of collectors. These contain tubes or panels with a heat-absorbing material and are often coated with a dark surface to maximise sunlight absorption.
  • Heat transfer fluid – Within the collectors, a heat transfer fluid, usually water or a mixture of water and anti-freeze, circulates through the absorber. As sunlight strikes the absorber, it heats the fluid.
  • Circulation system – The heated fluid travels through pipes or tubes to a heat exchanger or storage tank. In the case of heating water, this heated fluid transfers its heat to the water supply in a heat exchanger (or water tank), raising its temperature.
  • Water heating – In a solar hot water system, the heated water is stored in the dedicated insulated tank, ready for use. This preheated water supplements the need for traditional water heating methods, reducing energy consumption.

The whole system is a loop, so once the heat transfer fluid has transferred its heat to the water, it will circulate back to the solar thermal panels ready to be reheated by the sunlight.

Of course, this system only works while the sun is shining on the solar panels, therefore, solar water heating systems will not provide hot water all day, all year round.

It is estimated that solar thermal panels can produce around 80-90% of hot water in summer and 20-30% in winter, so you’re likely to need a boiler or immersion heater to help keep water warm when there’s no solar energy to do it.

How much hot water can solar thermal panels produce

solar panel diagram

Types of solar thermal panels

There are two types of solar thermal panels, with each one suitable for different situations:

Solar thermal flat plate collectors

The components of these solar thermal panels are a transparent cover, a water and anti-freeze fluid, a dark heat-absorbing surface, and a heat-insulating backing. The absorbing material can be made of polymer, which is better suited for colder climates because it can withstand freezing, or metal, such as copper, aluminium, or steel (copper is the most expensive, but it yields the best results).

Evacuated tube solar collectors

These solar thermal panels are made up of several reinforced glass tubes. To help prevent heat loss, a smaller tube is suspended inside each larger tube, creating a vacuum thermal insulation layer. The smaller glass tube is filled with water and anti-freeze fluid and has an interior coating of a light absorber, such as aluminium nitrate or titanium nitride oxide, to help maximise absorption.

Which one should you choose?

Selecting the right solar thermal panel for a property may depend on where it is located. Since vacuum tubes prevent heat loss, evacuated tube solar collectors are the most energy-efficient choice in cold climates. Flat plate solar collectors, however, do experience some heat loss. Nevertheless, evacuated tube solar panels run the risk of overheating and losing efficiency in warmer climates.

Evacuated tube solar collectors don’t require a lot of surface area. This means the panels themselves are smaller than flat plate solar collectors, so don’t need as much space. Yet, they produce the same amount of hot water as flat plate solar collectors.

Cost of solar thermal panels

When investing in solar thermal panels, the expense won’t just be the panels and installation. You’ll need to invest in the system as a whole to get the best results.

The total cost of the panels and their installation will depend on the type and brand that you use and how many are needed. Excavated tube solar panels are often slightly more expensive than flat plate solar panels.

The solar thermal system is also made up of a solar controller and pump. The easiest and most cost-effective way will be to purchase a complete solar thermal system, as everything you need will come together in one kit.

Additional costs that will need to be considered include a hot water tank. If you are currently using a combi boiler, you are unlikely to have a hot water tank in the building, so you will need to install one for the water to be stored and heated.

You will also need to check that the boiler you currently have will work alongside the solar thermal panel system being installed. If it isn’t, you will need to factor in potentially replacing the boiler too.

Luckily, once the solar thermal panels are installed, the costs are reduced significantly as their maintenance costs are low. It is recommended that you have the system serviced annually, but that should be the only consistent annual outgoings for your solar thermal system.

Government schemes to help

Currently, the Home Upgrade Grant is available for those looking to upgrade their home to be more environmentally friendly.

This allows around 45 local authorities to give a grant of up to £10,000 to households who are implementing changes that will improve their energy efficiency and reduce environmental impacts.

Advantages of solar water heating

There are several benefits of installing solar thermal panels in your home or business for solar water heating.

  • Renewable energy – Solar thermal panels utilise clean and renewable solar energy, reducing reliance on non-renewable resources for water heating.
  • Energy savings – By harnessing sunlight to generate heat, solar thermal systems can significantly lower energy bills associated with water heating.
  • Reduced carbon footprint – Using solar thermal panels for heating decreases greenhouse gas emissions, contributing to a greener and more sustainable environment.
  • Versatility – These systems can be adapted for various applications, providing both hot water and space heating in residential or commercial settings. They are also able to be fit with a solar PV panel system.

Disadvantages of solar water heating

While solar thermal panels and solar water heating offer many benefits, there are a few negatives that should be considered before diving right in.

  • High initial investment – The upfront cost of purchasing and installing a solar water heating system can be relatively high. This includes the cost of solar panels, installation, and additional components.
  • Sunlight availability – Solar water heaters rely on sunlight to generate heat. In regions with frequent cloudy days or limited sunlight exposure, the efficiency of the system may decrease, impacting its performance.
  • Backup systems – Solar water heaters are likely to require a backup heating system (such as a gas or electric heater) for periods of low sunlight or increased hot water demand. This backup adds to the overall system cost and energy usage.
  • Appearance – Some individuals may find solar panels aesthetically unappealing, which could be a concern, particularly in residential settings where the appearance of the property is a significant consideration.

Speak to our experts

To explore the possibilities of solar water heating for your property, reach out today! Call us for expert advice or to request a quote for a sustainable, cost-efficient solution tailored to your needs. Start your journey toward renewable energy now!

Call us on 0330 124 2941 or complete our contact form and we will get back in touch with you as soon as possible.

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