How Many Solar Panels Do I Need?

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✅ Three-bedroom homes need 8–10 solar panels

✅ Getting more efficient solar panels means needing less panels overall

✅ Your yearly electricity usage dictates how many panels you’ll need

Getting solar panels these days is an increasingly smart purchase – you’ll benefit from lower energy bills, shrinking your carbon emissions, and being less reliant on the grid to power your home. 

If you’re considering switching to solar power then, you’ll want to know how many solar panels your home will need.

Thankfully, we’ve got you covered, with a detailed guide explaining the number of panels you should get for your property, whether you can add panels to an existing setup, and if the number of solar panels increases the cost of installation.

How many solar panels does my home need?

Exactly how many solar panels your home needs will differ depending on factors in our helpful table above. While useful, this table is better used as a guideline — each home is different and this means solar panel requirements will vary. 

If you can’t figure out how many panels your home actually needs, you don’t need to worry that much. Your installer will be able to work out exactly how many panels your home needs during the consultation phase. 

What’s the best way to calculate how many solar panels I’ll need?

Thankfully, working out the approximate number of panels your home needs is a pretty easy process. Simply check how much electricity your home uses each year, which is done by multiplying your monthly energy bill by twelve. 

After you have your yearly energy consumption in kilowatt hours (kWh), divide it by 400 watts, which is the average output of most solar panels available on the market right now.

As an example, if your annual electricity consumption is 3,600 kWh, you should get around nine 400 w solar panels to power your home each year.

Please note that this’ll be an average energy consumption, because homes always use more or less energy each month depending on the time of year.

Should I aim to cover my entire roof with solar panels?

As a general rule of thumb, you should size your solar panel system to meet your present or expected electricity use. Installing solar panels this way means you’ll get the best value for money and importantly, a reasonable break-even point. 

Of course, you can still choose to cover your roof with solar panels. Doing so means you’ll probably generate more electricity than your annual consumption, but it’s typically not worth it from a financial point of view. 

You might be thinking it’s a good idea to oversize a system so you can sell excess electricity back to the grid. However, the amount you can make from this is almost always a tiny amount — especially when compared to the high cost of oversizing a solar panel system. 

Basically, it’ll make very little difference to the break-even point and you might even find yourself in a position where the payback time for your system is much longer. 

What affects the number of solar panels I need?

Every home is unique, meaning there’s a multitude of factors that impact how many solar panels your property will require. 

For example, you could have a north-facing roof that’ll need more solar panels to generate the same amount of electricity a south-facing roof could with less panels. 

  1. What type of solar panel you choose
  2. Where you live
  3. Your roof’s angle and direction
  4. Whether you expect your electricity consumption to increase in the future

See below for a more detailed breakdown of each of these points.

1. What type of solar panel you choose

Solar panels don’t come in one size or material — in fact, they vary greatly and the type of solar panel you choose will greatly impact how many you’ll need to power your home. Some solar panels are flexible and can be moulded around different shapes, but provide less power than fixed panels, for example.

The most efficient solar panels widely available on the market are monocrystalline panels. Using them means you’ll fill a smaller amount of roof space than with the aforementioned flexible solar panels, because they can provide more power per square metre of space used.

Conversely, opting for flexible panels (often called thin-film solar panels) will mean you’ll need more panels to reach the same or similar power output as you’ll get from monocrystalline panels. That means using more roof space, which can be a big no for people concerned about solar panel aesthetics. 

Plus, monocrystalline panels look much better (in our opinion) than thin-film panels, thanks to their sleek, black aesthetics.

2. Where you live

It’s no secret that the sun isn’t always shining in the UK, though you’d be surprised to learn there’s still a substantial amount of variation in the amount of sunshine hitting different areas in the country. 

Let’s say you’re a solar panel owner in the North of Scotland. You’re going to generate around 2,221 kWh of electricity each year. If you’re a solar panel owner in the South West of England, you’re going to generate a more impressive 3,023 kWh.

Basically, if you generate less solar power on average, your home will require more solar panels on its roof to reach the same power output as homes based in the south of England.

3. Your roof’s angle and direction


Where your solar panels face has an impact on the power they’re able to generate from solar energy. The angle they’re installed at affects power output too.

In an ideal scenario, you’ll want your solar panels pointing south, and be installed at an angle between 20° and 50°. This can be different if you don’t live in the UK, but for UK homes this is the optimal setup.

Generally speaking, the further your setup is from the scenario above, the more solar panels you’ll have to install to reach the electrical output you want. 

Also, for homes with flat roofs, fret not — you can still reach the optimal angle if your solar panels are installed on a mounting system to prop them up. 

4. Whether you expect your electricity consumption to increase in the future

Take into account whether you expect your electricity consumption to increase in the future, because if you do, it’s probably a good idea to get a larger solar panel system. This way, you can have a system capable of meeting your future needs without having to worry about expanding it at a later date.

For example, if you want to add green technology such as a heat pump or an electric vehicle charger, you’ll need a significantly larger solar panel system to meet their energy demands.

Be aware though, that even a bigger solar panel system can struggle to fully meet the needs of heat pumps and electric vehicle chargers. This is because they require a lot of electricity and adding them into a home’s energy mix means your solar panel system could strain to power everything in your home alongside them.

Can I add more solar panels at a later date?

It’s always possible to add more panels to an existing solar system, in case your electricity consumption goes up or your current system doesn’t meet your home’s energy needs. Though typically, an installer will make sure to properly size a system to power your home before they go ahead with the installation. 

If you do decide to add more panels to your solar system, it’s best to make sure they are the same type as the existing panels.

You’ll want to do this because different solar panels could have different wattages, which in a nutshell means your solar system will have a lower overall power output. Solar systems always prioritise the lowest wattage panels, which leads to the more powerful panels being deprioritised.

In layman’s terms, your solar panels will generate less power and you’ll get less benefits from your solar system.

Is installation cost affected much by the number of solar panels?

How many solar panels you install doesn’t actually affect the overall installation cost that much, so don’t decide to install less solar panels because of this. The main factors that have the biggest impact on what you’ll pay are scaffolding and labour. This can prompt some people to think about installing the solar panels themselves, but trust us when we say it’s not worth the risk. 

You can find yourself with a system incapable of meeting your home’s energy needs, on top of potentially inflicting damage to your roof, or causing a fire.

Damage to your roof can come from not knowing how much weight it can support, and causing a fire is often the result of incorrect wiring. Our advice is always hire a professional to install your solar panel system.

Does installation time increase the more solar panels you add?

Assuming you’re not installing an especially huge solar system, most installations typically take no more than a day to mount on your roof.

In fact, the average installation takes roughly four to six hours from start to finish. Use that time to make a cup of tea and have a think about how you’ll be making the planet a greener place to live by swapping to solar power!

How big are solar panels?

Almost all residential solar panels are rectangular, usually measuring two square metres or thereabouts (typically two metres long, one metre wide, and with an approximate thickness between three and five centimetres). 

Compact panels are becoming more common however, with several manufacturers starting to sell models better suited for smaller roofs. These panels are generally more expensive than ordinary models though, so keep this in mind.

For particularly compact panels, take a look at some of the following models:

  • Sharp’s 258.4W NQ-R Series — 1.29 square metres
  • Panasonic’s 300W N300 — 1.54 square metres
  • SunPower’s 370W X-Series X22 — 1.63 square metres

Another option to get around limited roof space is to go for high-efficiency solar panels, such as monocrystalline panels. As with compact panels, you pay more upfront for higher efficiency, but also that means you’ll break-even sooner because they generate more electricity.

Most high-efficiency panels offer conversion rates for generating electricity from sunlight at around 20-22%. Broadly that means one unit of electricity for every five units of sunlight.

How much do solar panels weigh?

Commercially available solar panels for home weight between 18 kg and 20 kg. This means a standard solar panel system consisting of 10 panels weighs around 190 kg – more than double two fully grown men.

That’s more than enough reason to hire a professional to install your solar panel system. Plus, as we mentioned above, they’ll be able to install your panels without issue.

If you live in a mobile home or a smaller, off-grid setup, you might want to think about getting flexible solar panels, which weigh considerably less — between 0.8 kg and 3 kg. Additionally, they can bend around corners and bumps which makes them much more versatile, albeit at a cost of efficiency.

What if I live alone in a large house?

You might live alone in a large house with a much smaller annual electricity consumption as a result. You’ll typically need less solar panels because of this — you can use our early calculation to work out how many you’ll need (divide your annual electricity usage by the average wattage of a solar panel).

Still, it’s not the worst idea to think about future-proofing your home with a system large enough to meet the needs of more people. You might end up selling your home, or passing it on to family. 

For the former, having a solar panel system can actually increase the value of your property, if you decide to sell it.

Conclusion

To summarise, you’ll roughly need the following number of solar panels depending on the size of your home:

  • Six panels for two-bedroom homes
  • Ten panels for three-bedroom homes
  • 14 panels for four-bedroom homes

Now all you need to do is to go out and get a solar system installed, to start benefiting from reduced energy bills, lower carbon emissions, and less relying on the grid for your electricity. 

We can help you with this, with our easy-to-understand form. Simply enter a few details about your home and we’ll connect you with our trusted installers. They’ll get in touch with bespoke solar panel quotes for you to compare.

How Much Money Can You Save With Solar?

Save up to 90% on your electricity bill
Sell excess energy back to the grid
Increase the value of your home

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