Is a 8kW solar panel system the right size for your home?
It can be a tricky job to get the sizing correct. On the one hand, it’s great to generate plenty of renewable energy, but at the same time you’re paying for added capacity. You also have to work out whether to capture any excess energy with battery storage or send it to the grid.
An 8kW solar panel array is a substantial system. It can provide energy for homes with above-average electricity demands and even for small businesses.
In this guide, we’ll help you figure out if an 8kW system is the one for you. We’ll take a look at the energy generation potential, costs and benefits. Whether you’re new to solar energy or have already considered smaller systems like 4kW or 6kW, this guide will equip you with everything you need to make an informed decision.
What is an 8kw solar panel system?
An 8kW solar panel system is a large array for a home install. This capacity is double the size of the average solar panel installation in the UK, which makes it suitable for homes with higher electricity demands. This capacity is also suitable for small businesses.
The ‘8kW’ or ‘kWp’ system refers to the peak output of the array under ideal sunlight conditions – this is the maximum amount of electricity the system can produce in perfect weather. Of course, this doesn’t happen all of the time, but these systems can operate at or near their peak during the longer summer days.
Unlike smaller systems, an 8kW system is capable of generating enough energy to cover most, if not all, of your household or business energy needs, even leaving some surplus to store in a solar battery system or sell back to the grid.
What do you get with an 8kW solar system?
Like all solar systems, an 8kW setup includes several important components that work together to generate and manage electricity efficiently. These include:
- Solar panels – Capture sunlight and convert it into direct current (DC) electricity.Â
- Inverter – Converts DC electricity into alternating current (AC), which can be used by your home or business. A 6-7kW inverter is often paired with an 8kW system for optimal efficiency.
- Brackets or mounting system – Securely attaches the solar panels to your roof, making sure they’re properly angled to capture maximum sunlight.
- Electrical components – Cables, isolator switches and other wiring necessary to integrate the solar panels into your home’s electrical system.
- Energy monitoring system – Allows you to track the real-time performance of your solar panels, providing insights into energy generation and consumption.
How much energy does an 8kw solar system generate?
An 8kW solar system can produce between 28-40kWh of electricity per day, depending on weather and location. Across the year, this means an 8kW array can generate around 12,000kWh of electricity, which is significantly higher than the average household use.
To put this into perspective, my own semi-detached household – consisting of two adults and one child (and a dog) – uses just under 2,000kWh of electricity per year. I haven’t got an electric car or electric-based heating yet, which means our gas usage is much higher.
The average home uses around 2,700kWh of electricity per year, meaning an 8kW solar system can generate almost 3 times the energy needs of an average home.
Here’s a breakdown of electricity usage for some common household appliances to give you a rough idea of how much electricity you might be using in a day. For more accurate figures, take a look at your recent energy bills.
- Refrigerator: 1-2kWh per day
- Television: 0.1-0.3kWh per hour
- Electric oven: 2-4kWh per hour
- Washing machine: 0.5-1kWh per load
- Electric vehicle charger: 7-10kWh for a full charge
- Air source heat pump: 2-5kWh per day (depending on weather and usage)
Is an 8kW system suitable for your home or business?
An 8kW system is suitable for:
- Homes with 4-6 occupants who use more electricity than average.
- Small businesses with moderate energy demands, such as offices, workshops or retail spaces.
- Electric vehicle owners who need to charge their vehicles at home.
- Energy-intensive homes with appliances like electric heating, underfloor heating, air conditioning or large kitchens.
In particular, if you’re looking to reduce your reliance on grid electricity and potentially become partially energy independent (or as close to fully as you can get), an 8kW system offers significant benefits – this is especially true when paired with battery storage. During peak summer months, it’s likely you’ll generate more electricity than you use, so storing the surplus energy in a battery means you can fuel your evening-time and morning electricity use too.
According to the Energy Saving Trust, solar panels can reduce your electricity bills by up to 70 percent. With an 8kW system, you can expect to save towards £1000 a year on your electricity costs, but this amount will increase if you add battery storage.
How much does an 8kW solar panel system cost?
The cost of installing an 8kW solar panel system can vary based on the quality of panels, the inverter and your roof setup. However, to give you a rough idea you can expect to pay:
- Between £10,000 to £15,000 for the panels, inverter and installation
- £4,000 to £6,000 for battery storage depending on the battery size and capacity.
It’s true that it’s a significant investment, but it’s important to consider the long-term savings you’ll achieve over the system’s 25-30 year lifespan. These savings will reach into the five figures. For more information, take a look at our solar panel cost guide.
Savings with an 8kW solar system
The return on investment for an 8kW system is particularly appealing in today’s energy market. As electricity prices continue to climb, your savings from solar energy increase in direct proportion. Over the past few years, we’ve seen significant rises in energy prices across the UK, making solar energy an even smarter long-term investment.
With an 8kW system, you can expect to save between £900 and £1,100 per year on your electricity bills, depending on your household’s energy use patterns.
In addition to these savings, the Smart Export Guarantee (SEG) allows you to sell any excess electricity your system produces back to the grid, offering a potential extra income of £200 to £400 per year. Whilst export rates vary between energy suppliers, some companies, like Octopus Energy, offer competitive rates for exported solar power.
According to the Energy Saving Trust, the payback period for an 8kW system is around 11 years, after which your panels will be generating income and savings for years to come. With an estimated lifespan of 30 years, your system will continue to deliver financial returns long after the initial investment has been recouped – hopefully you’ll be getting ‘free’ solar energy for the next 20 years. This payback period could be even shorter if you add battery storage and increase your self-consumption of solar energy.
And if you do happen to sell your house during this time, you shouldn’t be out of pocket as solar panels add between 4-14% value to a home.
Adding battery storage to maximise your solar array
Adding battery storage to your 8kW solar panel system can help maximise the efficiency of your system. It allows you to store excess energy generated during the day for use in the evening or on cloudy days.
A good size battery for most residential solar systems will be somewhere between 5 to 15kWh. This will allow you to store enough electricity to power your home during the night or on overcast days. For example, a 10kWh battery would allow you to run your essential appliances for several hours, even when your panels aren’t generating electricity.
By storing excess energy, you can significantly reduce your reliance on the grid. This can be especially useful in the UK, where solar energy generation fluctuates depending on the season. During summer, you may generate more energy than you use, whilst in winter generation will be much lower.
Additionally, battery storage allows you to take advantage of time-of-use tariffs, using stored energy when grid electricity rates are highest. Over time, this helps increase your overall savings and shorten the payback period of your solar investment.
Battery systems usually cost somewhere between £4,000 and £6,000 depending on capacity. For example, a 5kWh storage battery that’s suitable for a three-bed house may come in around £4,500 on average.
For a 8kW solar array, you’ll probably want a higher capacity battery. The Tesla Powerwall 2 and GivEnergy All in One both have a capacity of 13.5kWh with prices starting from around £6,000. Read more on battery storage costs here.
How many solar panels arre needed for an 8kw system?
The number of panels you’ll need for an 8kW solar panel system depends on the wattage of each panel. Here are some common configurations:
- 20 x 400W panelsÂ
- 21 x 380W panels
- 24 x 335W panels
- 27 x 300W panels
Whilst higher-wattage panels mean fewer installations and a more compact system, they tend to come with a higher price tag. Alternatively, lower-wattage panels are more affordable but require more roof space.
In terms of space, you’ll need roughly 26-45 square metres of roof space depending on the panel configuration you choose. Homes with limited roof space may benefit from choosing more efficient, high-wattage panels.
Where to install an 8kW solar panel system?
Before installing an 8kW solar system, it’s important to assess your roof’s suitability. Solar panels work best on south-facing roofs with a 30-40 degree pitch, as this orientation maximises sunlight exposure throughout the day. However, east- or west-facing roofs can still be effective, though they may generate 10-20% less energy than a south-facing system.
Another crucial consideration is shading. Trees, chimneys or nearby buildings can create shadows on your panels, reducing their efficiency. Even partial shading on one panel can affect the output of your entire system, depending on how your panels are connected. To reduce this issue, you may want to consider microinverters, which allow each panel to function independently rather than linked together in ‘strings’. We discuss this more in this post on solar panels in series or parallel.
When you start to get quotes, a MCS-certified installer will advise you on placement and best connection for your panels. The installation of an 8kW system should be straightforward enough, with most installations completed in 1-3 days. If you’re interested, check out these questions to ask your solar panel installer.
Should you go for an 8kW system?
An 8kW solar panel system is a great choice for large households that use a lot of electricity. It can be a smart investment to help you generate a lot of renewable energy for a reasonable price.
If you have high electricity use, need to charge electric vehicles or run energy-intensive appliances, an 8kW solar system – especially when paired with battery storage – could significantly reduce your reliance on the grid and protect you from future energy price increases.
An 8kW system has the potential to generate up to 12,000kWh per year. This is a lot of electricity, meaning it may even offer the opportunity to earn extra income through the SEG scheme.
For those with smaller energy needs, a 4kW or 6kW system may be a more appropriate fit. It’s all a matter of your current and future energy needs.
