Considering solar powered underfloor heating as a method of keeping your home warm and snug? There are several things to bear in mind before taking the plunge.
While both underfloor heating and many methods of harnessing the power of the sun to use as energy are both fantastic ideas, they don't necessarily always produce the results people expect when combined.
We reached out to the experts to find out exactly what is meant by solar powered underfloor heating, what the pros and cons of these kinds of systems are and whether there are any, more effective, alternatives.
What is solar powered underfloor heating?
Before delving into the benefits and disadvantages of solar-powered underfloor heating, it is important to explain exactly what it actually is.
"People often ask about solar-powered underfloor heating, like it’s a product you can go out and buy. In reality, it’s just standard electric underfloor heating being powered by solar panels on your roof," reveals Martyn Fowler, founder of Elite Renewables.
"The heating system itself stays the same. It’s the electricity source that changes," continues Martyn. "If you’ve got solar panels generating electricity, that power can run the underfloor heating system. So yes, in that sense, you’re using solar power to heat your home."
Founder of Elite Renewables, Martyn Fowler is one of the UK's leading renewable technology experts, working with heat pumps for the last two decades. His passion for decarbonisation matched with a deep technical experience of the technology make him one of the industry's go-to experts for all things renewable.
What are the benefits of solar-powered underfloor heating?
By combining solar panels and underfloor heating, there are several benefits to be had, although this very much depends on the type of house you live in.
"This set-up works best in homes that are already well insulated," explains Martyn Fowler. "If heat is escaping through the walls, roof or floor, the system won’t be as efficient."
Martyn goes on to explain the other advantages to this kind of set-up.
"Electric underfloor heating can be expensive to run on grid electricity alone," says Martyn. "If you’re generating your own energy, you can lower those running costs. It also makes your home more self-sufficient and reduces carbon emissions."
What are the disadvantages of solar-powered UFH?
Despite offering some advantages to homeowners, solar-powered UFH is not without its downsides.
"The main issue is timing – you tend to need heating early in the morning and in the evening, when solar panels aren’t producing much electricity," points out Martyn Fowler. "That’s why we recommend installing a home battery as part of the system. It stores energy from the day so you can use it later when you need it.
"Some people also charge their battery overnight on cheaper off-peak tariffs. That stored energy can then be used during the day, when electricity prices are higher."
There is also the fact that, during the winter, solar panels alone are highly unlikely to generate enough power (around 1kWh in fact), meaning you will need an additional source, such as an air source heat pump or gas boiler anyway.
Can you solar power wet underfloor heating?
So far we've only discussed using solar power for electric underfloor heating, but what if you want a wet system?
In this case, it is better to view solar panels as an additional source of power as opposed to one that will run the whole system. Your solar panels could, for example, contribute to the day-to-day running of your heat pump which would, in turn, power your underfloor heating.
The experts we spoke to felt that in this case, a gas boiler or a heat pump, combined with and partially powered by, solar panels would be the most effective solution.
Can you save money with solar-powered underfloor heating?
One of the main reasons people consider using solar panels to power their underfloor heating is to save money – but what, if any, savings can homeowners expect by taking this route?
"Electric underfloor heating usually starts from around £1,500. It depends on the size of the space and the type of system you choose," says Martyn Fowler. "It’s often cheaper to install than a wet system but more expensive to run without solar.
"If you’re also adding solar panels, the full set-up might cost £6,000 or more," continues Martyn. "But if you’re already planning on installing solar or a major renovation, it makes sense to include underfloor heating. It helps you get more value from the energy you generate and cuts down your reliance on the grid."
"Electric underfloor heating runs at close to 100%. That sounds impressive, and is better than a modern gas or oil boiler (typically 89%) but the problem is that, unless you’re buying on a time-of-use tariff at the right time, electricity is about four times the price of gas or oil per unit of heat output," picks up Simon Bones, CEO at Genous.
"Provided you’re on a suitable tariff, every unit of electricity that you generate and don’t use gets exported and your retailer pays you 15p a unit. So your ‘cost’ of using your own electricity is effectively 15p a unit," continues Simon. "But a unit of gas is typically about 7p a unit, so even if you did power your electric underfloor heating with solar power, it’s costing you 15p a kWh of heat whereas a modern gas boiler would be costing you (after efficiency losses) about 8p, or nearly half as much.
"Our heroic heat pump, at 400% efficiency, would be costing you less than 4p a kWh of heat, or half the cost of gas."
Simon is CEO and founder of Genous. He has first-hand experience navigating the retrofit world and has installed solar PV, renewable heating (both heat pump and biomass), smart control systems, insulation and performance glazing into various properties, as well as making the switch to electric vehicles. A Visiting Research Fellow at Bristol University in climate change science, Simon has an academic as well as business and personal passion for all things climate-change-related, and he has master’s degrees from Bristol and Oxford.
Is a heat pump better than solar panels for UFH?
If all of this has left you wondering whether you would be better off installing a underfloor heating with a heat pump, you might just be onto something, particularly if you want a wet UFH system.
"The reason a heat pump works is that, if it’s well designed and specified, you get about four units of heat for every unit of electricity (the rest comes from the air or another source of heat), so you use a quarter of the energy," explains Simon Bones. "And it should cost about a quarter as much to run as the electric underfloor heating.
"Heat pumps can feel intimidating and they do cost more than a gas or oil boiler in most cases. So since heat pumps use electricity, wouldn’t it be easier and cheaper to put in electric underfloor heating, maybe with some solar panels so you’d be making your own electricity?" continues Simon. "It may be cheaper to put in, but that doesn’t mean it’s sensible to do, or cheaper to run. In fact, unless you have a very small property with a very low heat load – or a heat pump can’t work for logistical reasons – we don’t think this is a smart thing to do."
FAQs
Can solar panels alone power underfloor heating?
So, the big question, can you power your underfloor heating using solar panels alone?
"The short answer is no," states renewables and ventilation installer David Hilton. "You need the most heat in winter and generate the most from solar in summer. In the 'in between' months you may get a little something.
"Electric UFH is less compatible with solar as it is often a constant resistance and constant load," continues David. "You also need to use the energy as it is produced or get a very big battery. At least with wet UFH you can heat up a store and use the heat later."
David is a renewables and ventilation installer, with over 35 years experience, and is a long-standing contributor to Homebuilding and Renovating magazine. He is a member of the Gas Safe Register, has a Masters degree in Sustainable Architecture, and is an authority in sustainable building and energy efficiency, with extensive knowledge in building fabrics, heat recovery ventilation, renewables, and also conventional heating systems. He is also a speaker at the Homebuilding & Renovating Show.
He is also director of Heat and Energy Ltd.
Interested in combining methods of powering your underfloor heating? Take a look at solar assisted heat pumps – they can be a great way to produce hot water for a home.
