A Guide to 3kW Solar Panel Systems for the UK

Written-by

Janet Richardson

Reviewed-by

Richard Burdett-Gardiner

Updated on

Sep 29, 2024

A Guide to 3kW Solar Panel Systems for the UK

Although a 3kW solar PV system for a residential property in the UK is under the standard size system of around 4kW, you can still save money, make your home more energy efficient and generate an attractive pay-back period. This size system tends to be ideal for small to medium sized homes that contain two or three people.

When you start looking into purchasing solar panels, there are a number of things that you should consider which we will detail out below. The likelihood is that you've arrived on this page due to a lack of space on your roof or simply a lower than average (2,700 kWh/s PA) electricity demand. The good news is that a 3kW system can be more than sufficient. 

What can a 3kW Solar Panel System Power?

The answer isn’t as easy as you’d expect. Many factors govern how much power any solar system can generate, and we’ll look at them all in turn. Before we get into it though we need to understand the jargon.

What does kW mean?
We’ll spare you the science lecture. In simple terms the abbreviation kW is a measure of the power a system can produce or use at a specific moment, while kWh measures the energy generated or consumed over time. Kilo means thousand, and the W is short for the surname of James Watt, the scientist who gave his name to a unit of measurement we use for electricity. To work out what a 3kW solar panel system can power, we need to know the average power used by homes in the UK. Since we Brits love a good statistic, this is an easy task.    

Average kWh in the UK
Here in Blighty, how much power we use ranges a lot. Generally, bigger homes with more occupants use more energy than smaller homes. We do know the average though. According to Ofgem, in the UK we use about 2700kWh every year or 7kWh per day. Now, at peak performance, a 3kW solar panel system produces 2500kWh per year or just under 6kWh per day. In theory then, 3kW solar panel systems can provide enough energy to power most homes, but of course, there are other factors to consider too. 

How much Electricity can a 3kW Solar Panel System Produce?

There are many issues that affect every solar panel system. Let’s look at them one at a time: 

Location
Solar energy depends on how many hours of sunlight your house will see. In the UK, despite being a smallish country, the amount of sun varies more than you might think. According to data from the Met Office, Bournemouth saw the most sun last year with an average of eight hours per day. However, it may surprise you to know that Bradford beat even the furthest reaches of Scotland to claim the title of gloomiest city. Alas, it’s true in 2023, Bradford boasted an average of just five hours of sunlight per day.  

Now, average is a big word and if you’ve lived in your home for a while you should have a rough idea of what to expect from your local climate.

Roof space and orientation 
Solar panels take up roof space and for the best results, you want your panels pointing towards the sun. The ideal position for the installation of the panels is on a south facing roof but east/west through south is considered usable. 

To install a 3kW solar panel system you need a roof big enough to accommodate 21 square metres of solar panels. Obviously, a 1kW solar panel system needs less space, while a 6kW solar panel system needs double the area of a standard 3kW installation.

The optimal pitch of the roof is anything between 40 and 12 degrees and of course, the less shading the better. 

Other considerations

Budget
A 3kW system will be less expensive than a larger system making it a good option for those with a limited budget. Make sure you get a range of quotes, prices can vary dramatically. See our guide for getting solar panel quotes.  
More on this below. 

Panel efficiency
The efficiency of a solar panel is based on the amount of sunlight reflected on a solar panel and what percent gets converted into electricity. Most solar panels claim efficiencies of 17-24%, generally speaking, you can expect to pay more for a higher efficiency panel. 

If roof space is an issue then less panels of a higher efficiency is often the best way to get the most out of the space you have. It's also worth mentioning that solar panels will lose efficiency over time. Check with your installation company and any manufacturers info for more details. 

Remember to have your panels cleaned from time to time as a layer of dust or bird mess will lower panel output. 

Of course, how much power you can generate from your system is also determined by the type of panels you choose. So, if you’re hoping for a 3kW Solar panel system, the space can vary depending on your panel type. We’ll look at those next. 

Carbon footprint
If your primary goal is to reduce your carbon footprint, a 3kW system will help significantly. The more electricity you generate from solar, the less you rely on fossil fuels.

Solar panel types

We’ll exclude solar thermal panels from this list as they work in a different way to photovoltaic panels. Photovoltaic panels or PV cells as they are often known, generate electricity from sunlight. In the UK, there are three main variants available.

Monocrystalline silicon solar panels
These jet-black sleek panels are the most effective and most common panels available in the UK.  They boast a 17-24% efficiency, the highest outside high-end panels like perovskite solar panels. We haven’t included the next-gen perovskite panels as they have only just come to market.

Monocrystalline cells cost more than budget panels and take up less space because they produce more energy. They are also harder to make and manufacturing these panels is a bit of an environmental disaster.

Polycrystalline, aka multi-crystalline, solar panels
With an efficiency of around 13%, polycrystalline solar panels are cheaper than their cousins. Unlike monocrystalline panels, they have a glassy blue appearance. Because of their lower efficiency, you’ll need more panels to create your 3kW solar panel system.

Amorphous/thin film solar panels
With a 7% efficiency, these thin-film solar panels are among the least efficient out there. That said, they are still the cheapest option. As they work well in low light, even moonlight they can generate power longer than other cells despite their poor efficiency. Their main disadvantage, besides their inefficiency, is the amount of roof real estate they need to generate comparable power.  

Energy consumption

Another factor that can determine if a 3kW solar panel system is suitable for your home is how you use your electricity.  We’ve looked at the UK average, but the size of system you need will depend on what you can do to lower your usage. Moving to more efficient appliances and changing the time you do certain activities can have a dramatic effect on how much power you need to take from the grid. Even little changes like making sure all your bulbs are energy saving can make a big difference on the amount of power you use.

The first step is to determine your average daily energy consumption in kilowatt-hours (kWh). You can find this information on your utility bills. As a quick guide, a 3kW system installed in optimal circumstances can generate up to 6-7kWh/s per day. This may not cover your needs but could go a good way towards subsidising your electrical consumption from the grid. Remember that you will need a battery system if you want to cover night-time usage. 

Smart Export Guarantee (SEG) for a 3kW Solar PV System

When you start looking into solar panels, the financial benefits that come with them are usually something that you take into serious consideration. The energy that is produced by the panels can not only help power appliances, but can also be sold back to your energy provider. Generally speaking, the larger the system you have installed, the more energy can be produced and sold. The Smart Export Guarantee (SEG) is a tariff that is agreed between yourself and your energy company that is paid to you for the electricity you send back to them. 

To qualify, you need a smart meter, and your panels and installation company must be MCS-certified. If in doubt, contact your energy provider. In most cases, under the Smart Export Guarantee (SEG), all unused energy generated is bought back by your energy provider. Solar panel owners earn money in return for every unit sent this way. Tariffs range between 3 and 23.5 pence per kWh, so it's worth shopping around as some providers offer more than others. Currently, Octopus has the best deal. At the moment, they offer up to 23.5p per kWh, but these tariffs shift all the time.

The Smart Export Guarantee replaces the UK’s previous incentive, known as the Feed In Tariff (FIT). The FIT program paid panel owners a stipend for all the energy they generated and not just the power they sent to the grid. Some local authorities, councils, and other bodies offer other smaller, local grants and schemes. If you’re interested in potential incentives near you, please check out our article on the costs of solar panels. 

The SEG aims to provide financial incentives for individuals and small businesses to invest in renewable energy systems by ensuring they are compensated for the surplus electricity they send back to the grid. Generally, the tariffs offered by energy companies is disappointingly low, you're paying 20-40 ppkWh (pence per kilo watt hour) these days yet the average tariff for the electricity you send back is 13 pp kWh and all they're doing most likely is sending it to your next-door neighbour. 

The scheme was set up by the government and requires energy companies to compensate property owners for the electricity they send to their supplier, it encourages the growth of distributed renewable energy generation and supports the UK's carbon reduction targets. 

Advantages of the 3kW Solar Panel System

Opting to go solar, doesn’t have to be about money. Sure, the financial benefits are great, but there are other good reasons to go solar. For a start, let’s talk about your carbon footprint. You’d have to still be on dial-up to have escaped the climate emergency facing our planet. If you care at all about the future of our species and the environment in general, then opting out of the fossil fuel industry is a no-brainer.

Moving to solar is an obvious choice, even if your array generates only 1, 2, or 3kW. Solar panel systems are an ideal, affordable option for anyone looking to take more responsibility for their environmental impact.  Another sensible reason to move to solar power is your well-being. Fossil fuel power creates and releases harmful chemicals. These particulates affect everyone in their radius and some of them cause cancers and other horrific health problems. The more people who choose to source their power from the sun rather than rely on burning our limited resources, the less we’ll need plants like these.

Adding value to your home with a 3kW solar PV system
As the popularity of solar power systems grows, the more value we as consumers place on it. It’s not rocket surgery then to say that adding a 1, 2, or 3kW solar panel system to your home will increase its sale-ability and value. Don’t forget, it’s not just the equipment that adds value, future buyers will also benefit from your Smart Export Guarantee (SEG) tariff. 

Future-proofing your 3kW solar panel system
The future is a big place and not many of us can claim clairvoyance as one of our gifts. So, if like most of the rest of the planet, you can’t tell fortunes, it’s a good idea to know the limits of your solar system. Honestly, thanks to global trends, the tech world seems invested in improving the efficiency of pretty much all appliances. In simple terms, its likely that in the years ahead, our washing machines and fridge freezers will require less power, while our solar systems produce more. So, if you’re worried about needing a bigger system in the future, don’t panic just yet.

Of course, you may decide to opt to use more electricity in your daily life by switching your car for an electric vehicle or another major life change. If that’s the case, then the good news is that most solar systems are modular at least to some degree. That said, adding more panels to your system may require a switch-out of the inverter.

Power cuts
It's not setup as standard in the UK, but if you arrange it with your installation company and get an inverter that can work off-grid, then solar panels can provide electricity to power your home in times of power cuts. A solar battery would be particularly useful if you get regular power cuts. 

Is a 3kW Solar Panel System Worth it?

In short, yes. Despite the initial layout, there are many financial and other incentives to mitigate the price. For a start, your solar system will save you money! Remember, a 3kW solar panel system could be able to produce most, if not all, of the energy you use. So, your electricity bills will plummet, but that’s not all!

Thanks to the global climate crisis, governments around the world have committed to reducing carbon emissions. In the UK, this means Government incentives for UK businesses and homeowners to switch their energy. As a result, there are a raft of grants, schemes, and other financial incentives available.

Generating a portion of your own power means that energy bills will be reduced over the foreseeable future, and so the investment will be earned back over a period of time. Although the pay-back period is likely to be longer than that of a larger system for those with average energy usage, it's still well worth investing in most cases.

A 3kW solar panel system can be sufficient for some households, but it may not meet much of the energy needs for others. Ensure to assess your energy consumption, roof space and budget to determine if a 3kW system is the right choice or if you should consider a larger system. Consulting with us, or a solar panel installation company in your area can help you make an informed decision.