Are you thinking about installing solar panels and wondering how many your home needs to drastically reduce your bills?
By 2025, over 1.5 million homes in the UK were using solar panels. While this accounts for only around 4.5% of households, the future looks brighter - which in turn could make solar more worthwhile.
After all, the government is aiming to triple the UK’s overall solar capacity by 2030.
As you might imagine, answering the question of how many solar panels a UK home requires is much like determining the length of a piece of string. But this time, the length of the string is determined by your home.
Ultimately, the number of solar panels you require will depend on the size of your property's roof and your household's energy demands. Of course, other factors can also play a role.
But, without further ado, let’s discuss the number of solar panels you’ll need to power your home.
Please note: solar system installations are very rarely the same, therefore there is no one-size-fits-all approach and the figures below are there to provide an estimate. To get an accurate quote, start here.
PS We offer MCS-certified solar panel installation nationwide. Simply answer these questions, get your fixed price and arrange your free design.
How Many Solar Panels Do You Need? Key Points:
The number of panels you require depends on your annual electricity consumption.
The size of your roof will also dictate how many panels you can install.
Other factors e.g. whether you intend to use it to charge an electric vehicle or heat your home also need to be considered.
You will unlikely be able to power your home entirely with solar i.e. go off the grid year round, but you can drastically reduce your energy bill.
In fact, according to the Energy Saving Trust, you could save around £465 a year on your bills by installing solar (based on the current Energy Price Guarantee).
You could also earn an average of £120 by selling excess energy via the Smart Export Guarantee.
If you’ve ever wondered if you’d use maths in real life, this is where your teacher has the last laugh.
How Many Solar Panels Does Your Home Need?
There are several key factors to consider when determining the number of solar panels required to power a home in the UK.
Typically, the number of solar panels you need will be between 10 and 15.
The main factors that determine the number of panels required are as follows:
Your household's annual electricity demands.
Your roof size i.e. this will tell you how many panels you can potentially install onto your roof.
If your energy demand is high, you’d better have a roof to match it.
Let’s say you calculate that you need 3.7 kilowatts worth of solar power to meet your household’s daily demands, then you should go with a 4kW system. Simple maths so far, but it gets worse.
If you were to go with 250-watt panels, you’d then need 16 panels to produce a 4kW system.
All in all, you should always go beyond your expected energy needs just to be on the safe side.
On average, households would approximately need the following solar panel systems:
Home Type and Number of Residents | Average Annual Electricity Use (kWh) | Size of System Required (kWp*) | No. of 350-watt Solar Panels |
Flat/1-2 people | 1,800 | 2kWp | 6 panels |
2-3 bedroom house/2-3 people | 2,900 | 3.5kWp | 10 panels |
Four bedroom home+/3 to 4 people | 4,300 | 5kWp | 15 panels |
Data source: Average annual electricity use data: Ofgem; kWp* stands for ‘kilowatt peak'. This is the amount of power that a solar panel or array will produce per hour in ideal conditions.
Remember: if you intend on charging an electric vehicle, as well as providing electricity for your home, factor this into your calculations.
For example, if your energy bill states that your household uses 4,000kWh/year, your EV may use an additional 5,000kWh/year to result in a 9,000kWh total electricity demand per year. When it comes to electricity, your EV is like a second home. When it comes to sleeping comfort, it sure isn’t.
For reference, according to the Energy Saving Trust, the most common solar installation in the UK is a 3.5 kilowatt-peak (kWp) system.
Creating a 3.5kWhp system using the average-sized solar panel size of 350-watt would require around 10 panels.
This system would be sufficient enough to power around half of the average household's annual energy demands.
If you don't have a solar battery, approximately 50% of the electricity generated by your panels will be unused by your household, as it may not coincide with the times when you require it i.e. in the evenings. That’s right, you probably still need electricity in the evenings, but your solar panels will be useless.
You can install a solar battery that can allow you to use around 30% more solar energy and according to the Energy Saving Trust, this could amount to saving £180 a year on your energy and reducing your carbon footprint by around 15%.
Combined with the Smart Export Guarantee, this could mean that you recoup the money you paid between 11 and 18 years - the exact timeline depends on how much you are earning via the SEG, how much electricity you use and when you use it.
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Can You Power a Home Entirely with Solar?
It's not possible to entirely power your home using solar since this would mean having energy when there is no sunlight e.g. in the evenings, as well as the dark days of winter. One alternative is to stop using electricity when there’s no sun.
A more popular option is to use battery storage, which would be able to store energy for use at night, however, even in winter, your solar panels are unlikely to generate enough electricity to recharge your battery to last.
For reference, in the UK there is five times more solar available during summer vs the winter. You probably intuitively knew that, but now you can be sure of this sobering fact.
How to Calculate the Number of Solar Panels You Need
In order to calculate the number of solar panels you need to power your home, your MCS-accredited installer will take the following steps:
Establish the electrical rating of the PV array in kilowatts peak (kWp).
Determine the postcode region.
Determine the array pitch.
Determine the array orientation.
Lookup kWh/kWp (kK) from the appropriate location-specific table.
Determine the shading factor (SF) using the shade factor procedure.
However, it's certainly worth being aware of the general calculation used to determine your solar array requirements:
Estimated Annual Output (kWh/yr) = Array size (kWp) x Solar Radiation Input Factor (kk) x Shade Factor (SF).
Step 1: Determine your annual energy use
The first step is to verify how much energy you use each year.
You can do this by checking last year's energy bill and making sure you didn’t buy an EV that could mess up your numbers.
For reference, according to Ofgem, the average electricity bill for a household of 2-3 is around 2,900kWh a year.
You can then divide this amount by 365 e.g. 2,900/365 = 7.94 kWh a day.
Check out our full in-depth article on whether solar is worth it in the UK.
Step 2: Determine The Number of Panels That Can Fit On Your Roof
In general, a size of 1.7m^2 is used for solar panels in the UK i.e. you calculate 1.7m^2 by the area of the roof.
For example, if the area of your roof is 12m x 6m = 72 m^2, divide 72 by 1.7m to give you 42.35.
This would mean that you can fit approximately up to 42 panels on your roof. Now, that’s a great way to outdo the neighbours.
Step 3: Determine the Array Size
To work out the solar array size you require, you can use the following formula:
Array size (kWp) = Panel Output (W)x Number of Panels.
For example:
The average array size in the UK is 3.5kWp = 350 Watt x 10 i.e. you would need 10 x 350 Watt panels to achieve the 3.5kWp array.
Step 4: Determine Your Solar Radiation Input Factor
The solar radiation factor (kk) is essentially the amount of sun your roof receives, which depends on the location of your home and the angle and pitch of your roof.
You do this by determining the following:
Determine the direction your roof faces.
Determine the angle and pitch of your roof.
Determine which zone you reside in.
Three simple steps that will have you bragging about your solar radiation input factor for many birthday parties to come.
Step 5: Determine Your Shade Factor
The ideal location is to have a roof with no shade at all.
If you don't have any shade, use 1 for this part of the calculation.
If you do, you will need to follow these steps on the MCS website.
Step 6: Plug in Your Numbers
Once you have followed the above procedures, you can then plug your numbers into the formula above.
If this is too complicated, simply use our Solar calculator here.
Still, learning about solar? Check out our guides on how many solar panels you need and how solar car charging works.
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.
Types of Solar Panels
We’ve already touched on the different types of solar panels in terms of their output; however, you can also separate them based on the photovoltaic materials they use. That’s another word you can incorporate into everyday conversation to impress others.
This may even have a small impact on the number of panels you’d need due to slightly different efficiency levels.
Those options are, namely, monocrystalline and polycrystalline.
Monocrystalline Solar Panels
One notable benefit of monocrystalline solar panels is that they have an efficiency rating of 15-20%, making them a bit more efficient than their polycrystalline alternatives.
Monocrystalline panels also use up less installation space and are more resistant to poor weather conditions.
So far, they’re a clear winner. Why would anyone choose a different option?
Price, as it turns out. These solar panels are more expensive, and they see poorer performance when temperatures go up. This leads to the irony of having a lower performance on the hottest summer days.
Polycrystalline Solar Panels
Polycrystalline panels have an efficiency rate of 13-17%. Yes, that’s less than monocrystalline panels but not a huge drop.
Moreover, in general, polycrystalline solar panels are less expensive and more tolerant of higher temperatures.
Cost of Installing Solar Panels
The most common solar installation in the UK is a 3.5 kilowatt-peak (kWp*) solar array since it will typically meet the energy demands of a three-bedroom house.
A 3.5kW solar panel system would typically require around 10 solar panels (at 350 W each) and cost between £5,000 and £10,000.
However, the Energy Saving Trust currently states the average cost is £5,500 for a 3.5-kilowatt system.
As mentioned, the higher the quality of solar panels you choose, the higher the final price, but thanks to their improved efficiency and power your home will be able to produce more electricity.
You can read our complete guide on solar panel costs here.
How Long Do Solar Panels Last?
On average, solar panels last around 20 to 30 years. In dog years, they’d have stopped counting.
By ‘lasting’ we mean that by this stage their efficiency will significantly reduce to the point that a replacement would be in order.
Naturally, solar panels, like boilers, tend to lose their efficiency over time.
So, a solar panel that is ten years old will not have quite the efficiency of a brand-new solar panel, even less so, if they are twenty-five or thirty years old. Just imagine how efficient you’ll be in thirty years, and we’re sure you can relate.
However, the longevity of solar panels also depends on factors like how well they are maintained and the quality of the panels, to begin with.
We have also reviewed the best solar panels and covered how long solar panels last in the UK.
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.
Get a Quote for Solar Today
Without boasting you should get your solar installed with us, here's why:
Thousands of Happy Customers: We boast an average score of 4.9 on Trustpilot, outperforming the market leader.
Which? Trusted Trader: Heatable is proudly recognised as a Which? Trusted Trader.
MCS Accredited: Our accreditation by the Microgeneration Certification Scheme (MCS) ensures high-quality standards.
Exclusive Panels: We offer REA Fusion solar panels, available only through Heatable.
Consumer Protection: As members of the HIES consumer code, we provide 2-year deposit protection.
Flexible Payment Options: Choose from multiple payment methods, including finance options.
Fixed Price Guarantee: Enjoy transparency with no hidden costs.
Save Your Quote: You can save your quote and decide later.
Bespoke Design Tool: Draw your own conclusion (literally) on whether solar is worth it for you, here.
