🔬 For decades, solar development was rapid

📅 The top solar panel efficiency has only gone up slightly since 2020

⚡ Power ratings have stagnated since the late 2010s

⛰️ Solar panels may have reached their durability peak

✨ Solar panel aesthetics may have also hit their ceiling

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Whenever you invest in your home and future, you want to get the timing right.

That’s why it’s a great idea to consider how rapidly solar panel and battery technology is developing, so you can buy the best products possible.

In this guide, we’ll run through the ways in which the efficiency, durability, power, and aesthetic appearance of solar panels have improved over time, and how far they have to go.

If you’re interested in how much you could save with a solar & battery system, enter a few details below, and we’ll generate a quick estimate.

How much has solar panel technology improved?

Solar panel technology is nearly unrecognisable from its origins in the late 19th century.

Researchers and manufacturers have made advancements in multiple fields to create the powerful, durable, sleek, high-efficiency panels we have today.

Efficiency

Scientists and manufacturers have increased the efficiency of solar panels exponentially since American inventor Charles Fritts created the first ever solar cells in 1883.

His creations, made by covering a semi-metallic element called selenium with a thin layer of gold and placed on a New York City rooftop, were 1-2% efficient.

In 1954, researchers at Bell Labs in New Jersey made the first commercially viable solar cell with silicon, laying the groundwork for modern solar panel systems.

That cell, which had an efficiency of around 6%, showed off its capabilities by powering a toy Ferris wheel and a radio transmitter.

Californian company Hoffman Electronics made a solar cell with 14% efficiency in 1960, and the race was on.

The 20% mark was passed in 1985 by scientists at the University of New South Wales, then in 1989, aerospace company Boeing surpassed 30% for the first time with a multijunction cell.

It took a bit longer to reach 40% efficiency, but in 2006, Californian company Spectrolab finally managed it.

The record high for solar cell efficiency now lies with the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany, where researchers made it to 47.6% in 2022.

However, it’s difficult to turn this progress with solar cells in laboratory conditions into solar panels with the same levels of efficiency.

The most efficient solar panels on the market at the moment are LONGi's Hi-MO X10 Scientist and JinkoSolar's Tiger Neo 3.0, which are both 24.8% efficient.

🤔 Thinking of going solar? Here's why a larger system makes sense ⬇️

How much will solar panel efficiency improve?

Solar panel efficiency rates are expected to improve extremely slowly, as companies make marginal gains each year or two.

There’s also a ceiling on the growth of most panels, as the theoretical efficiency limit of single-layered solar panels – which describes all modern solar panels installed on homes – is 33.7%.

Multi-layered panels like the perovskite-silicon tandem panel have the potential to raise the bar for solar efficiency, but they’re still mired in development and are facing significant stability issues.

In April 2025, Chinese solar manufacturer LONGi announced that it'd achieved 34.85% efficiency with a single perovskite-silicon cell.

And in June 2025, Chinese company Trina Solar revealed that it'd broken the efficiency record for a perovskite-silicon panel, hitting 30.6%, which is encouraging.

However, it’ll be many years – or decades, even – before these panels are widely available for domestic properties, and even longer until they’re affordable.

Durability

Solar panels have been extremely durable for several decades at this point.

A series of panels at Oldenburg University in Germany have generated solar electricity ever since they were switched on in 1976, and after being moved to the institution’s Energielabor building in 1981.

A representative from the university told us: “Most of the photovoltaic modules installed at the Energielabor in 1981 are indeed still working; they feed more than 3,000 kilowatt-hours of electricity into the grid per year.”

Considering these 336 solar modules had a power rating of 3.46 kilowatt-peak (kWp) when they were initially set up, this shows remarkable longevity. Between 1976 and 2011, the system’s efficiency rating only dropped from 8.55% to 8.2%.

Not every solar panel will last 50 years, and most will see their power output degrade as they age. You can expect the average panel to produce 87% of its original output after 30 years, according to our calculations.

The best monocrystalline panels will likely generate substantial amounts of electricity for around four decades, with some manufacturers already offering performance warranties guaranteeing your panels will produce 88% of their initial output after 40 years.

How much will solar panel durability improve?

Solar panels don’t need to become much more durable, considering the top models can already last about 40 years at a high level.

And that’s just an educated, possibly overly cautious prediction.

Solar panels of this quality only started being installed on domestic properties in the late 2010s, so there’ll be no definitive way of knowing their effective lifespan until the 2050s, at the earliest.

Power

Solar power ratings have come a long way.

In 1966, NASA launched its Orbiting Astronomical Observatory satellite into space with 53,000 solar cells and a peak power rating of just 0.7kWp, according to its report.

And let’s not forget that the NASA array was operating in space, where solar technology is significantly more effective.

Nowadays, a domestic system on Earth could easily reach that peak power rating with two solar panels that contain less than 200 solar cells between them (i.e. 52,800 fewer cells than NASA needed around 60 years ago).

NASA’s array also took up 17.4m². The same area on a modern rooftop could fit a system with a power rating of 3.9kWp – more than five times the capacity of NASA’s array.

The average solar panel’s watts per m² have come on leaps and bounds since the 1960s, and even between 2006 and 2018, when it rose from 141W/m² to 192W/m².

However, since then, development has stagnated around 200W/m², leading many manufacturers to discard the standard size used for many years and simply make larger panels.

This allows them to tell customers that their products have peak ratings above 500W or even 600W, without mentioning the fact that these panels are 3m² or larger.

So remember, when you’re looking at solar panels: the key metric isn’t the power rating; it’s watts per m².

Powerful panels with 200W/m² ratings are at least within reach of the average household now, unlike in 1955, when Hoffman Electronics sold a solar cell that cost around £16,000 per watt in today’s money.

Hoffmann Electronics would have gladly sold you enough solar cells in 1955 to cover your roof with a 4.6kWp system – but you would’ve needed a gigantic, very sturdy roof, and it would’ve cost you roughly £73.5 million.

Thankfully, the cost of solar panels has plummeted since then, and you can now buy the same system for around £10,000, on average – or with no upfront cost, if you use Sunsave Plus.

If you’re wondering how much a Sunsave Plus solar & battery system could save you, just answer a few quick questions below and we'll generate an estimate for you.

With the level of watts per m² remaining stable around 200W/m², solar panel manufacturers will keep producing panels with higher power ratings – but they’ll also be physically larger.

That’s not a meaningful advancement for households, who have to make the most of the limited space available on their rooftops.

As efficiency levels slowly rise over the coming years, the average panel’s watts per m² will too – but this increase won’t be significant enough that you should wait to get solar.

To learn more, check out our guide to solar panel sizes and dimensions.

Aesthetics

When it comes to appearance, there’s no comparison between past panels and current models.

For much of the 1970s and 80s, customers could only buy beige panels with large blue polycrystalline circles that looked like polka dots.

Panels composed of blue, polycrystalline material then became the norm until the early 2000s, when black, monocrystalline panels began to take over.

At this point, installers use black solar panels in the majority of new installations – and in recent years, all-black panels (complete with black busbars) have become the most popular variety.

There are also new types of solar panels that provide other options for the aesthetically minded customer.

You can get solar tiles, which replace all your roof tiles – but are 50% more expensive than regular panels – or roof-integrated panels, which cost about 10% more and require you to get rid of a section of your roof.

Alternatively, you could get transparent or thin-film solar panels, which are less conspicuous – but also less efficient, less powerful, and less durable.

How much will solar panel aesthetics improve?

Considering you can already purchase all-black solar panels, there isn’t much room for them to improve while remaining at their current efficiency level.

However, there is some movement in the market towards more variety when it comes to the colour of your panels.

Red, green, and purple panels are already available to domestic customers, though none of these models come with particularly high efficiency ratings.

Solar tiles could also be made to look even more similar to traditional roof tiles, but they already cost considerably more than solar panels, and any aesthetic improvements would raise this price even higher.

And as solar rooftop technology becomes an increasingly common site on UK homes, customers are likely to worry less about their tiles looking different.

Summary

Solar panels have gone from being an eccentric curiosity to a crucial tool in the fight against rising electricity bills and climate change.

Domestic panels probably haven’t yet reached their final form, but they're already so advanced in terms of power, efficiency, and aesthetics that any further gains would be far from essential.

It’s therefore worth investing in a solar & battery system now, so you can start saving straight away – a prospect that’s even better with Sunsave Plus, which comes with no upfront cost.

If you would like to see the savings you could get from a solar & battery system, just answer a few quick questions below, and we’ll provide an estimate.

FAQs

Are solar panels getting better?

Will solar panels ever reach 50% efficiency?

How efficient will solar panels be in 10 years?

How quickly are solar panels improving? [2025]

How quickly are solar panels improving?

🧮 There's an easy way to work out roughly how many solar panels you need

🏘️ The average three-bedroom home should get around 9-10 solar panels

⚡ Your annual and planned electricity usage affects how many panels you need

📈 If you opt for high-wattage solar panels, you won’t need as many

🌞 Get as many solar panels as you can

When you're investing in solar for your home, you want to choose the right number of panels. 

A system usually costs thousands of pounds upfront, and getting the size wrong can either inflate this cost further or needlessly limit your energy bill savings.

In this guide, we’ll explain how to calculate the number of solar panels you need, as well as how various factors affect the calculation.

To find out how much a solar & battery system could save you in the long run, enter a few details below and we'll provide an estimate.

How many solar panels do you need for your home?

The average household will usually need nine or 10 solar panels.

This should create a system that produces roughly as much electricity as your home consumes each year – though to maximise your savings and earnings, you’d ideally cover your roof with panels.

And if you're not an average home, how many panels you need depends on how much electricity your household consumes per year, and whether that figure's likely to rise in the near future.

Once you've worked that out, you should be able to calculate how much solar panels would save you on your energy bills.

<div style="text-align: center; font-size: 14px;">
<div style="display: inline-block; border-radius: 8px; overflow-x: scroll; max-width: 100%; margin: 40px auto; text-align: left;">
<table style="background: rgba(0,0,0,0.02);">
  <tr style="background: #4EE5D3; text-align: left; border-radius: 4px; font-size: 14px;">
    <th style="padding: 12px;"><center>Annual electricity consumption (kWh)</center></th>
    <th style="padding: 12px;"><center>Typical number of solar panels (450W)</center></th>
    <th style="padding: 12px;"><center>System size (kWp)</center></th>
    <th style="padding: 12px;"><center>Average annual output (kWh) *</center></th>
    <th style="padding: 12px;"><center>Average required roof size (m²) **</center></th>
    <th style="padding: 12px;"><center>Rough cost †</center></th>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>2,000</center></td>
    <td style="padding: 12px;"><center>6</center></td>
    <td style="padding: 12px;"><center>2.7</center></td>
    <td style="padding: 12px;"><center>2,295</center></td>
    <td style="padding: 12px;"><center>19.9</center></td>
    <td style="padding: 12px;"><center>£5,692</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>3,000</center></td>
    <td style="padding: 12px;"><center>9</center></td>
    <td style="padding: 12px;"><center>4.05</center></td>
    <td style="padding: 12px;"><center>3,443</center></td>
    <td style="padding: 12px;"><center>28.8</center></td>
    <td style="padding: 12px;"><center>£7,476</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>4,000</center></td>
    <td style="padding: 12px;"><center>12</center></td>
    <td style="padding: 12px;"><center>5.4</center></td>
    <td style="padding: 12px;"><center>4,590</center></td>
    <td style="padding: 12px;"><center>37.8</center></td>
    <td style="padding: 12px;"><center>£9,968</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>5,000</center></td>
    <td style="padding: 12px;"><center>14</center></td>
    <td style="padding: 12px;"><center>6.3</center></td>
    <td style="padding: 12px;"><center>5,355</center></td>
    <td style="padding: 12px;"><center>43.7</center></td>
    <td style="padding: 12px;"><center>£11,630</center></td>
  </tr>
    <td style="padding: 12px;"><center>6,000</center></td>
    <td style="padding: 12px;"><center>17</center></td>
    <td style="padding: 12px;"><center>7.65</center></td>
    <td style="padding: 12px;"><center>6,503</center></td>
    <td style="padding: 12px;"><center>52.7</center></td>
    <td style="padding: 12px;"><center>£14,122</center></td>
  </tr>
</table>
</div>
</div>

Table notes and sources

This table should give you a sense of how many panels are required for households with different levels of electricity consumption, though it's only a rough guide.

We've used 450-watt (W) solar panels, but the size of panel used by different installers will vary.

The number of panels you need will differ depending on a wide range of factors, including the panels' size, your roof's characteristics, how much sunlight your home gets, and your present (and future) electricity usage.

The exact number of panels you need will be best identified during a consultation with an installation expert.

How to calculate how many solar panels you need

To calculate roughly how many solar panels you need, the only piece of information you need to find is your annual electricity usage, which your energy supplier will usually share with you each year.

If you have an online account with your supplier, you may also be able to find your annual consumption that way. Otherwise, get in touch with the company.

Once you've found it, all you have to do is divide this number by 383, which is the typical annual output in kilowatt-hours (kWh) of a standard 450W solar panel in the UK.

 That'll give you a rough estimate of how many solar panels you need.

<div style="text-align: center; font-size: 14px;">
<div style="display: inline-block; border-radius: 8px; overflow-x: scroll; max-width: 100%; margin: 40px auto; text-align: left;">
<table style="background: rgba(0,0,0,0.02);">
  <tr style="background: #4EE5D3; text-align: left; border-radius: 4px; font-size: 14px;">
    <th style="padding: 12px;"><center>Step 1: Find your annual consumption (kWh)</center></th>
    <th style="padding: 12px;"><center>Step 2: Divide by 383</center></th>
    <th style="padding: 12px;"><center>Step 3: Round to the nearest whole number</center></th>
  </tr>
    <td style="padding: 12px;"><center>4,100</center></td>
    <td style="padding: 12px;"><center>10.7</center></td>
    <td style="padding: 12px;"><center>11</center></td>
  </tr>
</table>
</div>
</div>

However, if you haven’t been with the same supplier for at least 12 months – or if you've only recently moved into your home – you’ll need to use an alternative method. 

Unfortunately, it’s not as simple as multiplying your last month’s usage by 12, as you'll use much more electricity in some months than in others. Your winter usage will typically be higher than your summer consumption, for instance.

The best approach is to find out your consumption in two separate months: one in summer and one in winter. Then all you need to do is add them together and multiply the result by six to get your approximate annual usage.

After that, it's once again just a matter of dividing by the average amount of kWh generated by a 450-watt panel, which is 383, and finding the nearest whole number.

<div style="text-align: center; font-size: 14px;">
<div style="display: inline-block; border-radius: 8px; overflow-x: scroll; max-width: 100%; margin: 40px auto; text-align: left;">
<table style="background: rgba(0,0,0,0.02);">
  <tr style="background: #4EE5D3; text-align: left; border-radius: 4px; font-size: 14px;">
    <th style="padding: 12px;"><center>Step 1: Add a winter month's usage to a summer month's usage</center></th>
    <th style="padding: 12px;"><center>Step 2: Multiply by six</center></th>
    <th style="padding: 12px;"><center>Step 3: Divide by 383</center></th>
    <th style="padding: 12px;"><center>Step 4: Round to the nearest whole number</center></th>
  </tr>
    <td style="padding: 12px;"><center>370 + 302 = 672</center></td>
    <td style="padding: 12px;"><center>4,032</center></td>
    <td style="padding: 12px;"><center>10.53</center></td>
    <td style="padding: 12px;"><center>11</center></td>
  </tr>
</table>
</div>
</div>

Here’s an example

Solar panel calculator

This solar panel calculator can help you quickly work out roughly how many panels you should get for your home.

It works best if you know how many electricity your household uses per year, which you can get from your supplier – either through your online account, or in a physical bill.

If you have no idea though, that's also fine: we'll just ask you a few questions to get an idea of your usage, including whether you have a heat pump or electric vehicle charger.

We'll then rely on the average UK solar irradiance to work out the number of panels needed to meet this consumption level.

Calculator sources

The result you get from this calculator is just a rough indication based on your usage.

For a more accurate proposal that’s tailored to your needs, enter your details below and one of our solar specialists will be in touch.

Will you still need to buy electricity from the grid?

The solar electricity your system generates each year won't usually line up with when you actually use the most electricity.

Solar panels generate much more electricity in summer than they do in winter, at least in the northern hemisphere.

This contrasts with the way households typically use electricity, which is relatively stable, with a peak in winter and a dip in summer. 

So even if your system produces all the electricity you need over the course of a year, you may not be able to use it all – though a solar battery does help.

You'll usually rely on the grid for some of your electricity in winter, and export a large proportion of your solar electricity in summer.

You can earn money for this excess energy with a solar export tariff – and to choose the right tariff for you, check out our guide to the best solar export tariffs. 

On average, you could save 86% on your electricity bills with a solar & battery system.

What’s the minimum number of solar panels needed?

We generally recommend a minimum of six solar panels in order to make meaningful savings on your energy bills. With 450W panels, this would form a 2.7kWp system.

However, it's almost always worth getting as large a system as you can. Extra panels don’t tend to add much to your overall cost, but they can significantly boost your savings.

There’s no maximum number of solar panels you can install, so it's just a matter of how much space you have.

With a large system, you’ll generate excess electricity that you can sell to the grid. Export tariffs can already earn you hundreds of pounds per year, and they're getting increasingly profitable.

With systems lasting 30-40 years, you’ll also be protected against energy price rises and prepared for a future that may include an EV charger, heat pump, or air conditioning.

To find out more, check out our full guide: 4 reasons to get a larger solar panel system. 

The vast majority of sloped, residential roofs in the UK are strong enough to support a solar panel system, so there are normally no risks associated with adding lots of panels. It’s only once you go over around 25 panels that it’s worth considering an additional structural survey.

What’s the average number of solar panels per home?

The average solar panel system size in 2024 was 5.5kWp, according to Ofgem.

With 450W panels, this would make 12 the rough average.

However, many customers opt to cover their roof, to generate as much electricity – and as much income – as possible.

<em><center>Sunsave customer Richard opted for 18 solar panels on his roof</center></em>

Average residential solar panel system size UK, 2020-24

The chart below shows how the average size of a residential solar panel system in the UK increased between 2020 and 2024, based on data from Ofgem's annual SEG report. 

This trend towards larger system sizes displays a growing appetite for bigger arrays across the country, but is also indicative of advances in solar technology.

The average number of panels in a system has probably stayed roughly the same, as households still have a limited amount of roof space – but panels have become increasingly powerful.

Below are some solar PV system designs that Sunsave designed and installed in 2024 at homes across the country, all of which show large savings on their electricity bills.

Some of the designs include more panels than the household would require to match its consumption, because it’s best to make the most of your roof space.

After all, larger solar panel systems produce more savings, since you can just sell all your excess electricity to the grid on an export tariff.

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<div style="display: inline-block; border-radius: 8px; overflow-x: scroll; max-width: 100%; margin: 40px auto; text-align: left;">
<table style="background: rgba(0,0,0,0.02);">
  <tr style="background: #4EE5D3; text-align: left; border-radius: 4px; font-size: 14px;">
    <th style="padding: 12px;"><center>County</center></th>
    <th style="padding: 12px;"><center>Number of panels</center></th>
    <th style="padding: 12px;"><center>System size</center></th>
    <th style="padding: 12px;"><center>Electricity consumption</center></th>
    <th style="padding: 12px;"><center>Electricity bill savings</center></th>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>Kent</center></td>
    <td style="padding: 12px;"><center>12</center></td>
    <td style="padding: 12px;"><center>5.16kWp</center></td>
    <td style="padding: 12px;"><center>4,972kWh</center></td>
    <td style="padding: 12px;"><center>90%</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>Bedfordshire</center></td>
    <td style="padding: 12px;"><center>18</center></td>
    <td style="padding: 12px;"><center>8.01kWp</center></td>
    <td style="padding: 12px;"><center>6,000kWh</center></td>
    <td style="padding: 12px;"><center>120%</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>Hampshire</center></td>
    <td style="padding: 12px;"><center>14</center></td>
    <td style="padding: 12px;"><center>6.02kWp</center></td>
    <td style="padding: 12px;"><center>4,545kWh</center></td>
    <td style="padding: 12px;"><center>108%</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>Gloucestershire</center></td>
    <td style="padding: 12px;"><center>14</center></td>
    <td style="padding: 12px;"><center>6.16kWp</center></td>
    <td style="padding: 12px;"><center>2,270kWh</center></td>
    <td style="padding: 12px;"><center>154%</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>Dyfed</center></td>
    <td style="padding: 12px;"><center>16</center></td>
    <td style="padding: 12px;"><center>7.12kWp</center></td>
    <td style="padding: 12px;"><center>4,903kWh</center></td>
    <td style="padding: 12px;"><center>96%</center></td>
  </tr>
    <td style="padding: 12px;"><center>Northamptonshire</center></td>
    <td style="padding: 12px;"><center>17</center></td>
    <td style="padding: 12px;"><center>7.48kWp</center></td>
    <td style="padding: 12px;"><center>2,109kWh</center></td>
    <td style="padding: 12px;"><center>180%</center></td>
  </tr>
</table>
</div>
</div>

Table sources & notes

It’s possible to add more solar panels to your system later on, however it often requires additional work such as upgrading the inverter and/or rewiring the system, and you’ll also be paying for another round of scaffolding and labour. The most sensible approach from a financial perspective is to maximise your roof space the first time around.

What factors affect how many solar panels you need?

Here’s a list of factors that usually affect the number of solar panels you’ll need to power your home:

If your electricity consumption is going to increase soon

This is the main factor that'll help you work out how many solar panels you should get.

Your system should generate roughly as much electricity per year as you currently consume at home.  

Even with a battery, you won't be able to use all the solar electricity your panels produce – as they'll generate so much more in summer than in winter – but sizing your system in this way helps to maximise your profits.

2. If your electricity consumption is going to increase soon

<div style="text-align: center; font-size: 14px;">
<div style="display: inline-block; border-radius: 8px; overflow-x: scroll; max-width: 100%; margin: 40px auto; text-align: left;">
<table style="background: rgba(0,0,0,0.02);">
  <tr style="background: #4EE5D3; text-align: left; border-radius: 4px; font-size: 14px;">
    <th style="padding: 12px;"><center>Household setup</center></th>
    <th style="padding: 12px;"><center>Average annual electricity usage (kWh)</center></th>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>3-bedroom house</center></td>
    <td style="padding: 12px;"><center>2,700</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>3-bedroom house + heat pump</center></td>
    <td style="padding: 12px;"><center>5,900</center></td>
  </tr>
  <tr style="border-bottom: 1px rgba(0,0,0,0.1) solid;">
    <td style="padding: 12px;"><center>3-bedroom house + EV charger</center></td>
    <td style="padding: 12px;"><center>4,200</center></td>
  </tr>
    <td style="padding: 12px;"><center>3-bedroom house + heat pump + EV charger</center></td>
    <td style="padding: 12px;"><center>7,400</center></td>
  </tr>
</table>
</div>
</div>

If you’re expecting to increase your electricity consumption in the near future, it's worth considering getting a larger solar panel system to meet that rise in demand when it happens. 

Adding a heat pump or an electric vehicle charger, for example, will be better with a sizable solar panel system to help cover the increased energy consumption.

A heat pump for a three-bedroom household typically adds 3,200kWh to your total annual consumption, while an electric vehicle and charger will add around 2,000kWh, on average.

However, bear in mind that technology such as heat pumps and EV chargers use a lot of electricity.

Even a large solar & battery system will struggle to cover the majority of your electricity needs, so you'll still have to rely on the grid for some power, especially in the winter months.

For more information, read our guide to how the UK's electricity consumption level is increasing.

The direction your solar panels face affects the quantity of electricity they can generate – as does the angle they’re installed at. 

If you live in the UK, you’ll ideally want to have your solar panel system facing south, at an angle between 30° and 45°.

The further you are from this ideal situation, the more solar panels you’ll need in order to achieve the required quantity of electricity.

You can still generate lots of electricity throughout the year with an east-facing or west-facing solar panel system, but it’ll need more panels than a south-facing system to achieve the same output.

And if you have a large south-facing roof that comes with various obstructions – such as chimneys, skylights, and vent pipes – that cast areas of the roof in shade, you may have to use more panels on other sides of your roof to reach your desired output goal.

If you have a flat roof, you can achieve the optimal angle with a mounting system to prop the solar panels up, though most residential flat roofs in the UK aren't strong enough to support a solar array.

Since drilling into a flat roof is usually a bad idea, the system will need ballasts to secure it to the roof, which weigh around 80kg per panel.

This will usually make an array with 12 solar panels around five times heavier, which is too much for the average roof.

Check out our article on whether your roof is suitable for solar panels to find out more.

Despite the UK’s comparatively small physical size in global terms, there’s a surprisingly large variation in the amount of sunshine hitting different parts of the country. And this, of course, will affect how many solar panels you need in order to meet your consumption levels. 

You won’t be surprised to read that the more southerly parts of the UK, like Cornwall, Dorset, and Essex receive more solar irradiance than the northern parts. 

For instance, the south of England typically sees around 128 watts per square metre (W/m2) of solar irradiance each year, whilst the northwest of Scotland sees just 79W/m2.

Receiving less solar irradiance obviously means you’ll need more panels on your roof to achieve the same power generation as those basking in higher quantities. 

Some solar panels are much more efficient than others, which can greatly affect how many you need.

A panel's efficiency directly equates to how much electricity it can produce per square metre (m²).

For example, the 24.8% efficient LONGi Hi-MO X10 Scientist generates 248W of capacity per m² in standard test conditions. That's 43W more than the 20.5% efficient REC N-Peak 2.

With a 10-panel system, that's a 430W gain. In the UK, this will let you generate 366kWh more per year, on average – and if you use that to replace grid electricity, it'll save you about £100 extra.

So the more efficient your panels are, the more you'll save.

This is particularly important if you have limited roof space, but higher efficiency panels can boost your returns in any scenario.

The most efficient solar panels all have ratings above 20%, which means they turn more than one-fifth of the natural light they receive into electricity.

Advances in the field are very gradual though, with companies making marginal gains every year or two.

Does a battery change how many solar panels you need?

A battery doesn’t change how many solar panels you need, no matter its size.

However, it allows you to make the most of your panels, both because you can use even more of the electricity they produce, and because you can take advantage of better export and import tariffs.

These include high-paying export rates like Good Energy Solar Savings and Octopus Flux. You may also be able to sign up for Good Energy Solar Savings Exclusive or Intelligent Octopus Flux, though these tariffs come with extra requirements.

Here’s how to work out how many solar panels you need for your home, and the key factors to consider.

Josh Jackman

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