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How Many Solar Panels Do I Need

If you're thinking about switching to solar energy in the UK, then you will need to do a little groundwork before deciding if the move is right for you.

One of the most important things is working out the number of solar panels you need.

To do this, you'll need to consider a range of factors like:

  • roof space
  • how much energy usage is common in your house per year
  • the cost of installation and what you can realistically afford

There are more factors to consider, of course, but to help you today, we here at Skylamp Solar have put together a guide to help you answer that age-old question for yourself: Just how many solar panels do I need?

Join us below as we work through some common examples, and then talk you through the factors to consider so you can work it all out for yourself!

Number Of Solar Panels Commonly Needed Per Property Type

Please note: We have calculated the following examples based on a solar PV system - hybrid systems and thermal systems aren't applicable in this case.

Below we'll look at the average house by property type to talk about the number of solar panels needed per solar panel system.

Remember, though, that this is just an average - you and your property may require more solar panels or less.

Solar Panels 1

One-Bedroom Flat

The average one-bedroom flat will require a 1kWp solar array, which typically uses 3 solar panels.

One/Two-Bedroom House

The average one-bedroom house/two-bedroom house will require a 2kWp system, which typically uses 6 solar panels.

Three-Bedroom House

The average three-bedroom house will require a 3.5kWp system, which typically uses 10 solar panels.

Four/Five-Bedroom House

The average four-bedroom house/five-bedroom house will require a 5kWp solar array, which typically uses 14 solar panels.


The solar panel output efficiency will vary per system and will therefore impact how many kilowatt hours of electricity it can produce. You'll also need a solar battery storage system in place to make the most of the solar system you've got for maximum efficiency.

In all, the examples above will cover around 50% of the household's annual energy usage.

You can make your solar system more efficient if you use battery storage, so any excess electricity made during energy production that you can't use yourself can be sold back to the national grid via the smart export guarantee (SEG) scheme.

That way, you'll cover 50% of your energy consumption (which will reduce energy bills by 50% also) and then be able to make even more money back by selling excess energy.

How Much Power Can A Solar Panel Produce Per Year?

To work out how many solar panels do I need, you first need to understand how much energy one solar panel can produce.

Installing solar panels is great, but if you don't know how much electricity it can produce, then you don't know how many solar panels are needed.

One 350W solar panel in the UK can produce 265kWh per year. This is based on efficient solar panels, how much solar panels produce in less than ideal conditions can vary...

Factors Affecting Solar Panel Efficiency

Residential solar panels installed in the UK will produce a different amount of energy - 265 kilowatt hours per year is only the average. Things like:

  • solar panel size
  • location of property
  • roof location (a south facing roof will always work better than a north facing roof)
  • number of peak sunlight hours in your area (how much sunlight you typically get)
  • solar panel pitch (and how much sun it can get)
  • weather patterns

Will all affect that number.

Conventional solar panels may have an average, but not all conventional panels produce the same amount of electricity annually.

For the sake of the example below, we will stick to the 265kWh average, but just know that your solar panels on your roof may produce more or less. Exactly how much energy it will be is difficult to say.

To help you understand how the energy produced by a single solar panel impacts on the number of panels needed in a solar system, let's look at a standard three-bedroom house below...

Panel Solar

How Much Energy Does A Typical Three-Bedroom House Require Per Year?

According to Ofgem, the average usage for a three-bedroom house (the average UK home) is around 3000kWh per year. This is medium usage. You may use more electricity (and therefore require more panels and more solar power), or less depending on your household (and therefore require fewer panels). We'll talk more about figuring out your own usage below.

For now, though, you can see that the average three-bed house will use 3000kWh per year in terms of annual electricity usage.

If you wanted to cover your electricity bills in their entirety, then you would divide your total usage (in this case 3000kWh) by the average energy produced by a solar panel in the UK (265kWh) to get the total number of solar panels you would need (3000 divided by 265 = 11.3 - so 12 in total to cover it all).

If you didn't want to rely on solar energy alone, then you would need to work out how much solar power you would like to rely on before working out how many panels you need.

How To Calculate How Many Solar Panels You Need

If you're asking 'How many solar panels do I need', then the chances are you want specifics for your house, right? Not just the averages we've provided above.

To help, we here at Skylamp Solar have put together a foolproof way of working out how many solar panels you need.

Please note: The method we describe below is based on UK averages still. There is no way of providing you with the exact number of panels you will need without coming to your property and collecting some additional data. A solar professional would be able to do this for you before fitting any solar panels on your property to give you an idea of how many panels you'll need for your solar system. More on this later.

The Solar Panel 1

Annual Energy Usage

Before you start to work out the number of panels you will require, you first need to work out your annual electricity usage.

If you want the energy generated by your solar panels to cover the majority of your energy usage (and therefore energy bills), you'll need to know your exact energy use per year - not just the average amount for the average household.

Thankfully, working out your annual energy usage is easy - all you need is your 12 month electricity bill OR 12 months' worth of electricity bills.

If you have an annual electricity bill spanning 12 months, then great. This will tell you exactly how much electricity you use per year.

If you don't have one, simply add together 12 months' worth of bills, and this will tell you your annual usage.

Divide By 265kWh

As soon as you know your yearly use, you can then divide that number by 265kWh (the average amount of solar energy solar panels produce per year in the UK), to give you how many solar panels you'll need.

Here is a worked example to help:

  • Your household's annual energy usage = 3650kWh
  • Divide that number by 265kWh
  • Number of solar panels needed: 13.7 (or 14 to cover your total usage)

Covering Total Usage Vs Other Options

Not everyone will want to cover their annual usage with solar energy alone. In this case, you will need to work out your target daily average.

For example, you might only want to cover 50% of your usage.

Taking the example above, then, here's how you would work out how many solar panels you would need to cover your target:

  • Your household's annual energy usage: 3650kWh
  • Your target: 50% of energy use
  • Divide 3650 by 2: 1825kWh
  • Divide that number by 265kWh
  • Number of solar panels needed to cover 50% of usage: 6.8 (6 or 7, depending on what you would like)

Measure Roof Size

Perhaps the most important of the three key factors you need to consider before making an initial investment in solar panels is your roof size.

How much space you have available to you will also impact how many solar panels you can realistically have.

It's all well and good knowing that you need six solar panels to reduce your carbon footprint significantly, but that's not worth knowing if they can't fit on your roof.

Measuring your roof space is vital.

How Large Is The Average Solar Panel?

Solar panel size matters too, of course, or else how will you work out how many solar panels can fit on your roof?

Typically, a single solar panel in the UK will take up around two square metres of space.

In order to work out if your roof is suitable for the solar panels you are thinking of installing, you'll need to divide the roof space available to you - in square metres - on your south facing roof (south facing will have more peak sunlight hours and therefore will be more efficient), by 2.

This will show how many solar panels you can realistically fit up there.

If you can fit fewer panels than you need, then you may simply have to rely on more energy from typical sources. These are all things you can discuss with a professional installer before deciding how many solar panels are needed for your property, though.

The BEST Way To Work Out How Many Solar Panels You Need

Speaking of professionals, there is a much better way of working out how many solar panels are needed at your property, and it involves no maths or calculations on your part.

The answer?

Contacting a professional solar panel installer.

By speaking with the professionals, they will be best placed to advise about the solar panels you require, how many, and also discuss installation costs with you. They may also be able to give you a better idea of how soon your solar panels will start paying for themselves.

The best way to work out the number of panels needed is to talk to the pros and have them inspect your property. That way, you'll get the perfect answer for you.

Solar 1

A Note On Hybrid Vs Thermal Vs Solar PV Systems

Today's post has been focussed on solar PV systems rather than hybrid and thermal systems for a reason.

Thermal solar panels are designed to heat water for your home, so working out how many panels are needed here is slightly different and is best left to the professionals when you talk with them. Typically, though, 2-3 solar panels will be enough for a 200-300L hot water cylinder, which will usually cover most households' daily usage.

For hybrid solar systems, working out how many panels are needed becomes even more complicated. Because the hybrid system heats water and provides electricity, it's difficult to split out the amount of electricity it produces and the amount of heat it provides (although a 4kW system will typically help save £1000 per year on electricity and £150 on heat and water).

As hybrid systems develop, working out how many solar panels are right for your system may become easier, but for now, it's best left to the advice of the pros. Only solar PV systems currently have enough research and reliable averages for us as consumers to be able to work out how big our system needs to be.

Related post: What size solar battery do I need?

Related post: What size inverter do I need for solar panels?


Your Next Steps

If you've worked out the number of solar panels you're likely to need for a solar system at your home, then the next best thing you can do is contact a solar panel installer to have them confirm the number and provide professional advice.

Only with the assistance of the professionals can you know for sure the total number of solar panels you will need.

Stick to the advice we've provided here at Skylamp Solar, though, and you'll be able to know roughly how many you will need before the pros get there, allowing you to determine if their advice is sound or not.

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