For homes with larger energy needs, a 7kW solar panel system can be a powerful and efficient addition. At this size, it can be capable of covering a high percentage of your energy needs.
But this comes with a trade-off between energy generation, requirements and up-front costs. Is a 7kW solar panel system really the size you need?
It can be a tricky one to get right and it’s important to do your research. This guide aims to help you with your decision. We’ll discuss everything you need to know about 7kW solar panels, from how much electricity they generate to installation costs, space requirements and savings.
What is a 7kW solar panel system?
A 7kW system is on the large size when it comes to residential solar panel arrays. It’s almost double the average solar panel system size in the UK, which is around 4kW. Although that said, we think this average is going to increase over the coming years as the electrification of our homes, heating and cars continues.
Being labelled as 7kW, this refers to the peak power output of the panels under ideal conditions – full sunlight, at the perfect angle and with a temperature of 25oC. These are known as Standard Test Conditions (STC).
A 7kW system can theoretically produce up to 7 kilowatt-hours of energy in one hour under those perfect conditions. It’s thought that average conditions in the UK result in an output that’s around 85% of these STC.
Just like other solar panel arrays, there are several components that need to be installed including: the solar panels themselves (usually on the roof but can be elsewhere), an inverter or several microinverters to convert DC electricity generated by the panels into AC electricity, some form of mounting system or brackets, as well as all of the cables, connectors, switches and fuses to link everything together.
A key benefit of a 7kW system is that it’s large enough to generate significant amounts of electricity, yet small enough to fit on most residential roofs. It makes it a good option for medium to large homes who use a lot of electricity.
How much electricity does a 7kW solar system produce?
Ok, so you know a 7kW system can produce a large amount of electricity, but just how much?
This answer is that it depends on several factors These include:
- Time of the year
- Location in the UK
- Orientation of your roof
- Angle of the panels
On average, a 7kW solar panel system will produce between 7,500 and 10,500kWh of electricity per year. Here’s a rough month-by-month snapshot of potential daily and monthly output to give you an idea of how much this output can differ across the year.
| Month | Estimated daily output (kWh) | Estimated monthly output (kWh) |
| January | 10-12 | 310-360 |
| March | 15-20 | 450-620 |
| June | 25-30 | 750-900 |
| September | 20-25 | 620-750 |
| December | 8-10 | 250-300 |
During the summer, when sunlight is at its peak, a 7kW system can produce between 21 and 30 kWh per day, perhaps even a little more on the longest days. The months between May and August will produce around 40-50% of your total solar production.
In the winter, output drops to around 8-10 kWh per day, reflecting the shorter days and less intense sunlight. This is still a relatively significant amount and about the daily electricity use of an average home.
Can a 7kW system power your home?
On average, a standard UK household consumes around 3,700 kWh per year – well below what a 7kW system can generate. For this energy consumption, a smaller 4kW solar panel array might be sufficient.
If you’re interested in a 7kW system though, it’s likely that your energy needs are higher than these averages. Whether a 7kW solar array can cover your requirements all depends on how much energy you use. It’s best to check your energy bills and annual statements to get a good understanding of how much energy you use and when.
Some of the most energy hungry devices and appliances in modern homes include:
- Electric vehicle chargers – According to the UK Department of Transport, a home charger for EVs needs to use around 3.6kWh per day or 108kWh per month to meet the average miles travelled.
- Heating and cooling systems – Electric heating, such as underfloor heating, heat pumps and electric radiators, are efficient systems, but can use a significant amount of daily energy when added together. It’s common for this to be well over 10kW per day depending on your use.
- Household appliances – Tumble dryers, dishwashers, washing machines and electric showers are some of the most energy consuming appliances. You can get energy efficient eco versions that reduce energy requirements.
It’s highly unlikely you’ll be going off-grid with a 7kW – although this of course depends on the type of home you live in. But even with a large 7kW system, it’s likely you’ll still need a connection to the national grid to draw on power during low-production periods.
How many panels are needed for a 7kW system?
The number of solar panels you’ll need for a 7kW system depends on the efficiency and wattage of each panel. Solar panels come in different wattages, usually ranging from 300W to 450W. Some of the top solar panel manufacturers can hit wattages closer to 500W now.
On average, a 7kW system requires around 30-40m² of roof space. Here are some of the most common panel configurations to reach this output:
- 20 x 350W panels
- 18 x 390W panels
- 16 x 440W panels
This flexibility with panel output means you can tailor your solar setup based on your roof size and available space. Higher-wattage panels tend to be more efficient, which is particularly useful if you have limited roof space, but they may come at a higher price.
When considering space requirements, it’s also important to think about the way your roof faces:
- South-facing roofs offer the best conditions for solar energy production in the UK, as they receive the most sunlight throughout the day.
- East or west-facing roofs aren’t as ideal as south-facing roofs and output may be reduced by 10-20%. However, they can still generate a good amount of electricity.
- If your roof space is limited or not suitable for solar panels, a ground-mounted system is a good alternative, particularly for homes with larger gardens or unused outdoor space.
Cost of a 7kW Solar System
The cost of a 7kW solar panel system will depend on several factors, including the quality of the panels, the type of inverter used and the complexity of the installation. On average, the cost of a 7kW system in the UK ranges between £8,500 and £12,000.
This biggest cost associated with an array is of course the solar panels. High-efficiency monocrystalline panels are more expensive than polycrystalline but are more efficient and will generate more power in a smaller area.
An inverter is one of the most important components of your solar system, responsible for converting the DC electricity generated by the panels into usable AC electricity. The cost of an inverter for a 7kW system can range from £1,000 to £2,000. Many companies are now opting for micro-inverters associated with each panel rather than one inverter for the whole system. The benefit of micro-inverters is that each panel operates independently, meaning shading on one panel doesn’t impact the entire system.
Labour costs are a major addition, but something you can’t get away from. These can vary depending on the complexity of your roof and how many people are on the installation. Scaffolding costs can add a chunk to the total too.
The installation process for a 7kW system usually takes between 2 and 3 days, depending on the complexity of your roof and the number of panels. It’s important to choose MCS-certified installers to make sure the system is installed to a high standard and complies with regulations.
Any good solar panel quote you receive should include all costs, with nothing hidden that’s going to rear its head later down the line. This gives you peace of mind that you know everything is taken care of. You can find much more detail on solar panel costs here, as well as the key questions to ask your solar panel installer.
Some homeowners also opt to include a solar battery with their system. Batteries can store excess electricity generated during the day for use at night or during cloudy periods. The cost of a solar battery for a 7kW system starts at around £5,000, depending on the capacity and brand. More on batteries shortly.
How much will you be saving?
The payback period for a 7kW solar system ranges around 10 years or less. This is the amount of time it will take for the savings on your electricity bills to cover the upfront cost of the system.
It may seem like a long time, but remember that solar panels can have a life expectancy of around 30 years, meaning you’ll be getting 20 years of free electricity once it’s paid off. Plus, if you do sell up and move, solar panels can add value to your home in the region of 4-14%.
With a system that produces around 9,000 kWh of electricity per year, you could save up to £1,000 per year on your electricity bills, depending on your energy usage. This saving is likely to increase in the future as energy prices continue to increase, meaning you’ll be potentially saving north of £20,000 over the solar panel lifetime.
Additionally, with the Smart Export Guarantee (SEG), you can sell any excess electricity your system generates back to the grid. Rates vary by provider, but you can expect to receive anywhere from 2p per kWh exported to 30p per kWh with the special Octopus Energy tariffs. These SEG exports can further reduce your payback period and increase your overall return on investment.
Do you need a solar battery with a 7kW system?
It’s not essential to have a battery storage for your 7kW system, but we think it is a fantastic addition as they can significantly improve the benefits of going solar.
A solar battery allows you to store excess electricity generated during the day and use it when the sun isn’t shining, such as during the evening or on cloudy days. This is the main benefit of a solar battery, but there are plenty of others too. For example, a battery helps you to become more energy independent, use a guaranteed renewable energy source and will help you reduce your bills further.
A good size battery capacity for a 7kW system ranges from 10 kWh to 15 kWh. This will allow you to store enough energy produced during the day for evening use and potentially in the morning. Check out our guide on calculating the right size battery storage size for your solar setup.
The cost of a battery starts at around £5,000, making it a significant but worthwhile investment. Find more info on battery storage costs.
Could a 7kW system be right for you?
A 7kW solar panel system is an excellent option for larger homes with higher energy demands. It provides plenty of electricity to significantly reduce your reliance on the grid, lower your electricity bills and make a meaningful contribution to reducing your carbon footprint.
If you think a 7kW system may be too big, a 4kW or 5kW may be better. On the other hand, you can upgrade to a larger 8kW or even 10kW solar system if you have very large electricity uses.
As you assess your options, make sure that you get quotes from multiple, accredited solar installers. They’ll give you detailed assessments of your home’s solar potential and advise you on whether a 7kW system is the right choice for your circumstances.
