Solar thermal is one of the most straightforward and cost-effective renewable technologies available to Belfast homeowners. Unlike PV solar — which generates electricity — solar thermal panels use the sun's energy to heat water directly, feeding into your hot water cylinder and reducing the amount of gas or oil your boiler needs to burn. The result is lower fuel bills and a meaningful reduction in your home's carbon footprint.
Thinking about solar thermal for your home?
Get an honest assessment from a local OFTEC registered engineer — no obligation.
What Is Solar Thermal Heating?
Solar thermal panels — also called solar water heating panels — are fitted to your roof and connected to a hot water cylinder inside your home. A fluid (water mixed with glycol antifreeze) circulates through the panels, absorbs heat from the sun, and transfers that heat to your cylinder via a heat exchanger. On a good day, your solar thermal system can provide all the hot water your household needs entirely for free.
Unlike PV solar, solar thermal doesn't require large roof space or generate electricity. It focuses on doing one job well: heating your water. This makes it a practical option for a wider range of Belfast and Lisburn homes than PV systems, and the installation is typically less complex and less expensive.
Benefits of Solar Thermal
- High efficiency — up to 80% system efficiency under good conditions
- Free hot water — your boiler does less work, especially in spring and summer
- Lower fuel bills — reduced gas or oil consumption year-round
- Small roof space required — unlike PV solar, thermal panels are compact
- Compatible with multiple fuel sources — works alongside gas boilers, oil boilers, back boilers and heat pumps
- Long system lifespan — well-maintained solar thermal systems last 20+ years
- Reduced carbon footprint — less reliance on fossil fuels for hot water
Is My Home Suitable for Solar Thermal?
The ideal installation is on a south-facing roof pitched between 30 and 50 degrees — this gives maximum sun exposure throughout the year. However, solar thermal panels can also be installed on east or west-facing roofs, although they will receive less sun exposure and produce less heat as a result.
Your home will also need a hot water cylinder to store the heated water. If you currently have a combi boiler with no cylinder, a new solar cylinder will need to be installed as part of the project. Kieran will assess your property and advise honestly on whether solar thermal is a good fit for your home and your hot water usage.
The Installation Process
In most cases, a solar thermal installation is completed in a single day with minimal disruption to your home.
Site Assessment
Kieran visits your home, assesses your roof orientation, current hot water system and cylinder setup, and gives you an honest recommendation and clear quote.
Scaffolding & Panel Installation
Scaffolding is erected where needed. The solar thermal panels are fitted to your roof in the optimal position.
Cylinder Installation
Your existing hot water cylinder is removed and replaced with a new solar-compatible cylinder. If you already have a suitable cylinder, this step may not be necessary.
System Fill & Commissioning
The panel circuit is filled with the correct water and glycol mixture, the system is commissioned and tested, and you're walked through how it operates.
Solar Thermal and the Thermal Store Cylinder
If you have a larger property with multiple heat sources — for example, an oil boiler combined with a back boiler, solar thermal and potentially PV solar — a thermal store cylinder may be the right choice. Unlike a standard unvented cylinder, a thermal store is designed to accept heat from several sources simultaneously, using whichever is cheapest or most available at any given time.
This is ideal for homes looking to maximise renewable energy use while keeping a fossil fuel backup for reliable heating throughout winter. Kieran can advise on whether a thermal store or a standard solar cylinder is the better fit for your setup. See also our hot water cylinders page for more detail on cylinder types.
Solar Thermal Servicing & Repairs
Like boilers, solar thermal systems benefit from annual servicing to maintain efficiency, check the glycol levels and inspect the panel connections. Kelly Heating NI carries out solar thermal servicing and repairs across Belfast and Lisburn. If you have an existing solar thermal system — installed by another company or as part of a previous property — we can service it and bring it back to full operation if needed.
Solar Thermal vs PV Solar — Which Is Right for You?
The two technologies are complementary rather than competing. Solar thermal heats your water; PV solar generates electricity. If your main goal is to reduce hot water costs, thermal is typically the more cost-effective starting point. If you want to generate electricity to offset your wider energy use, PV is the right route. Some Belfast homeowners install both, and a thermal store cylinder can manage energy from both systems together.
See our PV solar panels page for information on electricity-generating solar installation in Belfast.
Frequently Asked Questions — Solar Thermal Belfast
Yes — solar thermal works even on overcast days, as it captures diffuse as well as direct sunlight. Northern Ireland gets enough solar radiation to make thermal systems genuinely useful, particularly for spring, summer and autumn hot water. Your boiler provides backup on darker winter days.
In most cases, yes — a solar-compatible cylinder is needed to store the heated water. If you currently have a combi boiler with no cylinder, this is an additional cost. Kieran will assess your current setup and advise at the site visit.
Most installations are completed in one day. More complex setups involving a new cylinder and thermal store may take longer — confirmed at your site visit.
Yes — solar thermal integrates well with oil boilers. The solar system handles hot water when there is sufficient sun, and your oil boiler provides backup when needed. This is one of the most common configurations in greater Belfast.
Yes — annual servicing is recommended. This includes checking glycol levels, inspecting connections and testing system performance. Kelly Heating NI provides servicing for both new and existing solar thermal systems.
What Our Customers Say
Trusted by Belfast & Lisburn Homeowners
"Kieran is heating engineering perfection at a reasonable price. He recently fixed my ailing gas boiler and it's working like new. His attention to detail was extraordinary as he unravelled the plethora of mistakes made by previous companies. Highly recommended."
"Kieran and Grahame reinstalled a poorly commissioned unvented system, ensuring it was installed properly to all necessary standards. They arrived exactly when they said they would and worked virtually non-stop. Completed to an excellent standard."
"Really excellent service from Kieran, right from the first point of contact through to the work being undertaken. Everything was very professional and he gave excellent advice. I cannot recommend him highly enough."
"Kieran fitted a new boiler for us — arrived on time, did an immaculate job and explained everything before he left. Very fair pricing and no hidden extras. Would absolutely use again and recommend to anyone."