How do you heat water with solar energy? Here we explain, as well as answer questions regarding costs and limitations.
Just as solar panels can be used to generate electricity to power household appliances, it’s also possible to employ solar energy to produce hot water. And not just in the way the sun melts your ice cubes.
More specifically, solar water heating does not rely on solar panels that are used to turn the sunlight into electricity, instead solar thermal panels can harness the sunlight to warm water.
Solar water heating utilises a combination of a solar thermal tube/panel system and a hot water or immersion heater.
But how much can you expect to pay? And is it worth it in the UK (since we’re not exactly known for our sun hours)?
Let’s explore...
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Solar Water Heating Key Points:
Solar water heating systems use sunlight to heat water for domestic use.
Types of collectors include flat plate and evacuated tube collectors.
Heat transfer fluid transfers heat from collectors to the water in a storage tank.
Solar water heating systems can meet a significant portion of hot water needs.
Costs vary based on system size, type, and complexity.
Benefits include reduced energy bills and lower carbon emissions.
Maintenance is minimal, but periodic checks are recommended.
Assess feasibility based on sunlight availability, roof orientation, and shading.
Having a roof is a prerequisite for solar water heating. Check to make sure you have one (fastest when it rains).
What is Solar Water Heating?
A solar thermal system or solar water heating system uses a solar collector (tube or panel) to heat warm before it can be stored in a hot water cylinder or thermal store for domestic use.
This hot water can then be used just like hot water produced by a central heating system (e.g., for showers or washing dishes in the sink).
However, solar water heating can’t realistically meet a household’s entire hot water demands - especially if you also shower in winter.
For that reason, a solar water heater would act as a means of supplementing the hot water generated through your central heating.
For example, it is often paired with an immersion heater or a boiler to provide supplemental heating when required.
But how does solar water heating work exactly?
How Does Solar Water Heating Work?
A solar water heater employs solar collectors to harness the energy of the sun.
These collectors can come in the form of either:
Evacuated tubes.
Flat plate collectors.
The tubes, more specifically known as evacuated tubes, are an array of glass tubes that are typically fitted on top of a property's roof, although they can also be ground mounted or installed onto a south-facing wall.
The flat plate collectors work in a very similar way to evacuated tubes. But they’re flat and shaped like a rectangular plate.
Either way, solar collectors turn the sun’s infrared light into heat. And since they have water and glycol inside, the heat gathered can be used to generate hot water.
This heated water will then make its way to either a thermal store or most likely, an aptly-named hot water cylinder.
It will then be available to supplement your home's hot water needs.
Still learning about solar panels? Explore our helpful guides on various topics, including solar panel grants, payback periods, the mechanics of solar energy, determining the number of panels you need, and solar car charging solutions.
Cost of Installing a Solar Water Heating System
So, how much would you likely pay to have solar water heating installed? Less than you’d like to pay, probably.
The price would depend on various factors, of course, but on average, households pay about £3,000 to £5,000 to have such a system installed.
With that said, the cost will depend on factors such as:
The size of the solar water heating system (i.e., the number of solar collectors being installed).
The quality of the solar water heating system.
The type of roof you have and how accessible it is.
Where in the UK you are located.
How much you tip your installer (not common)
*Why does your location matter? This is because labour prices differ throughout the country. For instance, some of the most expensive labour prices are found in the southeast of England, while prices are (on average) lower in North England, Scotland, and Northern Ireland.
Here is the average cost of having a solar water heating system installed by house type:
System Size | No. of People in Home | Estimated Cost* |
2m² | 2-3 | £2,500 to £3,000 |
3m² | 3-4 | £3,000 to £3,500 |
4m² | 4-5 | £3,600 to £4,100 |
5m² | 5-6 | £4,200 to £4,900 |
6m² | 6-7 | £4,900 to £5,500 |
*These estimated costs factor in both labour and supply costs.
How to Pay for Solar Water Heating
The Streets knew it: A Grand Don't Come for Free - and neither do solar water heaters.
As you can see, solar water heaters don’t come cheap.
However, there are some ways of bringing down the cost of installation.
Purchasing a Solar Water Heater on Finance
Some companies allow homeowners to purchase a solar water heating system on finance once certain criteria are met.
Purchasing on finance is just another way of saying buy now and pay later. Which is preferable to overpaying now and buying later.
Usually, you’d need a good credit history to be eligible for this or at least no signs of bad credit over the past several years.
However, the details will vary depending on the company. What’s more, purchasing on finance usually means paying interest.
So, while this approach could save you plenty of money in the short term, it would likely cost you more in the long run.
Check out our complete guide on the costs of solar and whether solar is worth it in the UK here.
Explore a Solar Case Study: Check out an insightful Q&A session featured in one of our detailed case studies on domestic solar panels. Hear directly from a Heatable customer in the UK and gain valuable perspectives on their experience here.
The image above shows a 23-panel solar installation, carried out by the MCS-certified solar team at Heatable, featuring the REA Fusion2 solar panels.
Using a Loan
Another solution is to take out a bank loan.
Again, you’ll likely need to meet specific criteria to be eligible for a loan, and of course, interest will also apply. As we all found out in 2008, banks aren’t charitable institutions.
While purchasing an appliance on finance can sometimes come with zero interest, loans are virtually never free of interest.
Aside from taking out a loan, if you have a credit card, you may be able to use this to pay for a solar water heating system.
However, whether you want to buy now and pay later, take out a loan, use a credit card, or a combination of two or all three of these approaches, you should make sure that you can afford it.
If in doubt, it’s best to wait and save more before installing a solar water heater.
What about the RHI scheme?
Unfortunately, the domestic renewable heat incentive (RHI) scheme closed to new applicants in March 2022. If you were an applicant before then, we mostly wonder why you’re reading this article.
It offered both an upfront payment when a household joined the scheme as well as yearly incentive payments.
This meant that under the RHI scheme, households could effectively save hundreds of pounds per year in heating costs if having a solar water heating system installed, rather than £40 to £100.
We have also reviewed the best solar panels and covered how long solar panels last in the UK.
Pros and Cons of Solar Water Heating
So, what are the benefits and disadvantages of a solar water heating system?
Let’s take a look:
Pros of Solar Water Heating:
Reduces your heating bill
First and foremost, a solar water heating system can lower your heating bills which is people’s favourite activity with bills. After all, it costs nothing to run a solar water heater.
This means that if you have, say, natural gas heating, using a solar water heater to supplement your home’s hot water production would likely save you around £40 to £60 per year.
If you use another primary means of heating your home (e.g., oil, electricity, or LPG), you may save somewhere in the region of £50 to £100 a year in heating costs.
Significant benefits in the summer
While a solar water heating system would likely meet around a quarter of your hot water needs in the winter, it could meet the majority of your water needs (perhaps about 90%) in the summer months. And not only because you’re bound to spend more time outside…
Lowers your carbon footprint
As with solar energy in general, a solar water heating system will mean fewer greenhouse gases entering the atmosphere. Fewer greenhouse gases mean colder winters, which also means you get more use out of your solar water heating. It’s a win-win!
Cons of Solar Water Heating:
Expensive upfront cost
As you saw earlier, having a solar water heater installed isn’t cheap.
Regardless of the size and type of system being installed, you’ll surely need to spend thousands of pounds. In any list of pros and cons, that’s a con.
The only exception would be if you were to use one of the alternative payment methods discussed in the previous section.
It takes a long time to pay for itself
With average annual heating savings of just £50, it would likely take many decades for a solar water heater to pay for itself.
In fact, for the average three-bedroom semi-detached house, it would take almost a lifetime (yours, not the system’s) to pay for itself. And leaving a legacy to the next generation is one thing, but a solar water heater probably isn’t that high on anyone’s list.
So, clearly, if you want a solar water heater, it makes sense to do so as a very long-term investment and as a way of improving your home’s energy efficiency and lowering your carbon footprint.
The output will vary
Aside from the fact that solar water heaters won’t likely be able to meet all your hot water demands, the output of a solar array will vary depending on the weather.
After all, solar panels produce a lot more energy on bright sunny days than they do on overcast ones.
Next Steps For Your Solar Journey:
When planning to install solar panels for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:
To dive deeper into these topics, head over to our advice section, check out our YouTube channel for informative videos, or read a customer case study to see how others have benefited from their solar installation.
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