Solar panel arrays can come in a wide range of sizes. For homeowners, it tends to be a trade off between how much energy you want to generate and your budget.
A popular approach for many UK homes is to install a 5kW solar panel system. Being slightly above the average installation capacity, a 5kW system is suitable for most medium to large homes. Could this be the right size for your home?
This guide will take a look into the world of 5kW solar panel arrays, how much they cost, how much energy they can generate and other factors that you need to consider.
What exactly is a 5kW solar panel system?
A 5kW solar panel system is a robust and fairly substantial installation capable of generating a good amount of power for your home. The ‘5kW’ is the system’s peak power output under ideal ‘Standard Test Conditions’, which takes into account cell temperature, solar irradiance and air mass. This is sometimes written as kilowatt-peak (kWp).
Under ideal sunny conditions, a 5kWp system working at maximum capacity for one hour will produce 5 kilowatt-hours of energy. This is why kWp and kWh are often used interchangeably with solar panels.
There are several key parts to a 5kW solar setup, including the photovoltaic (PV) panels themselves totaling 5kW and the solar inverter, which converts the direct current (DC) power generated by your panels into alternating current (AC) electricity that your home can use. The inverter is usually sized smaller than the panel capacity to optimise performance under varying conditions. For example, a 5kW solar system is typically accompanied by a 3.5kW inverter in the UK.
You also need the brackets and mounting hardware to secure the panels to your roof, as well as electrical wiring and control switches.
How many panels make up a 5kW system?
The number of panels in a 5kW system can differ. It all depends on the wattage of individual panels. You can achieve a capacity of 5kW, there or thereabouts, in a number of ways:
- 14 x 350W panels = 4.9kW
- 13 x 385W panels = 5.005kW
- 12 x 420W panels = 5.04kW
- 11 x 450W panels = 4.95kW
The choice of configuration can depend on a number of factors. For example, if you have limited roof space, you might have to go for the more expensive, but more efficient, higher wattage panels to reach the desired capacity. This may help if you plan on expanding the capacity of your array in the future.
If you’ve already chosen an installer, they might only have a certain panel size in stock. Rather than waiting for a new delivery, it’s sometimes better to adjust the plans. Available roof space: If your roof area is limited, higher wattage panels can help you achieve the desired output with fewer units.
What to expect from a 5kW system in terms of electricity generation?
In the UK climate, a 5kW solar panel system usually generates around 4,250kWh of electricity annually on average. This average fluctuates by location, for example in the south of England this figure can be closer to 5,000kWh, whereas in Scotland it may be under 4,000kWh.
According to Ofgem, a household with 4 to 5 people has a typical annual electricity use of 4,100kWh – just under what a 5kW system would produce on average. The annual production of a 5kW solar system translates to a daily average of 11.6kWh, which is just above the 6-10kWh average that most homes use in the UK.
A major point to understand is that actual production varies significantly with seasons and weather conditions.
- Summer months (May to August) – around 40-50% of total annual production
- Spring and autumn – a combined total of 40-50% of annual production
- Winter months (November to February) – just 10-15% of the annual total
On particularly sunny days, especially during summer, a 5kW system could quite easily produce 15-20kWh of electricity. On the other side, in the winter months you might see production dip to just 10-15% of the annual total, leaving you with an energy gap in terms of production and use.
Will a 5kW system meet all your energy needs?
A 5kW solar panel system is well-suited for medium to large households, typically those with 4+ bedrooms. Its output can significantly reduce, potentially even eliminating, your reliance on the mains grid for your electricity.
Consider these common household appliances and their energy consumption:
- Washing machine: 600-2000W per cycle
- Electric oven – between 1,000W – 5,000W per hour
- Electric hob – between 1,000W and 3,000W per hour
- Heat pump: 800-5000W per hour, depending on the season and demand
- LED TV: 50-100W per hour
- Laptop charger 50-100W per hour
- Electric vehicle charger: 2000-7000W per hour
With a 5kW system’s daily output of 11.6kWh on average, you could potentially power most of these appliances across the week. But we know that solar production doesn’t always match up with energy consumption patterns.
For example, your panels might be generating maximum power at midday when nobody is home and household energy use is low. The vast majority of this good, renewable energy will be sent to the grid. Meanwhile at 6pm when everyone is home and your energy demands peak, solar panel production is low and you have to buy energy from the grid.
This is why pairing your solar panels with battery storage is such a good idea.
Should you add battery storage to your 5kW system?
Given the potentially high energy production of a 5kW system, battery storage becomes an increasingly attractive option.
In our example above, it makes complete sense to send and store the excess energy generated on sunny days in a storage battery. As solar energy is the cheapest form of electricity you can get, storing it up to use later on will significantly help to reduce your electricity bills. It’s thought that a battery will help to increase your solar energy use by upto 80%. Read more on the benefits of solar battery storage.
For a 5kW system, a battery capacity of 5-7kWh often provides a good balance. On a sunny day, it’s highly likely that you’ll fully charge your battery when no one’s home. If you have a 7kWh, you then have all of this ‘free’ energy to use during the evening, overnight and in the morning if there’s any left before the sun starts shining again.
Prices for these residential storage batteries range from £3,000 to £5,000. Whilst this does add a large amount to your initial investment, it can dramatically improve your system’s overall efficiency and speed up the payback time.
When considering battery storage, it’s important to analyse your energy consumption patterns and typical excess production. This will help to make sure you choose an appropriately sized battery that maximises your benefits without unnecessary expense. It’s important not to oversize or undersize your battery as this will reduce its efficiency.
It’s entirely possible to start with just solar panels and add battery storage later to spread out the costs.
Costs and savings of 5kW system
Installing a 5kW solar panel system in the UK costs between £7,000 and £10,000 on average. This price includes all of the components and installation. Although this is a lot of money for most households, the potential for long-term savings far outweighs the initial costs.
A system of this size can cut your energy bills by over £650 a year. Additionally, you may earn income through the Smart Export Guarantee (SEG) by selling excess electricity back to the grid. The average here is around £200 but it can be more or less depending on your energy use and if you have a battery or not.
The payback period for a 5kW system generally ranges from 6 to 12 years, depending on factors like:
- Energy prices – As grid electricity costs rise, your savings increase, potentially shortening the payback period.
- Consumption patterns – The more of your generated electricity you use directly, the greater your savings.
- Export rates – Higher SEG rates can contribute to faster payback. For example, on certain Octopus tariffs, they’ll pay five times as much per kWh than some other suppliers.Â
- System performance – Factors like panel efficiency and installation positioning will influence energy production.
After the payback period, you’re essentially generating free electricity for the remainder of the system’s 25-30 year lifespan. This long-term perspective is crucial when evaluating the financial benefits of solar power. If you do go for a battery, remember, these only have a lifespan of around 15 years, so you’ll have to buy two during the lifetime of your panels.
If you decide you want to move house, solar panels can increase your property value too. Studies suggest that homes with solar installations can add between 4-14% in value to a home.
Space requirements and installation
A 5kW solar panel system requires a good amount of roof space – somewhere between 32-38 square metres. The exact area needed depends on the efficiency of chosen panels, with higher-efficiency models taking up less space.
In an ideal scenario, solar panels will be installed on a south-facing roof with a 30-40 degree pitch to maximise sun exposure. However, east or west-facing roofs can also be suitable, although this comes with a slightly reduced output (15-20% less than south-facing roofs). It’s also possible to install PV panels on flat roofs.
The installation process for a 5kW system usually takes 1-2 days. This includes putting up the scaffolding for safe roof access, mounting the brackets, installing the panels and inverter, wiring everything up and testing the system.
It’s essential that you use a certified Microgeneration Certification Scheme (MCS) installer for quality assurance.
What about planning permission?
In most cases, installing a 5kW solar panel system doesn’t require planning permission in the UK. Solar panels tend to considered ‘permitted development’ unless:
- You live in a listed building
- Live in a conservation area
- Your panels will stick up from the roof surface by more than 20cm
For any doubts, please check in with your local planning authority before going ahead.
Is a 5kW solar panel system the one for you?
A 5kW solar system offers an excellent balance of output and cost for many UK households. It’s particularly well-suited if:
- You have a 4 bedroom home
- Your annual electricity consumption is around 3,800-4,500kWh
- You have enough roof space
- You want to reduce your monthly energy bills
When paired with battery storage, a 5kW system can provide a high degree of energy independence. In the summer, you might be able to go ‘off grid’ for days and weeks at a time. This system also has the potential to support energy-intensive applications like EV charging and can contribute to powering heat pumps. That said, larger solar systems are likely to be needed for complete self-sufficiency all year round.
If you’re considering solar power, a 5kW system represents a good investment in sustainable energy. Whilst the initial costs are higher than smaller systems, the increased energy production can lead to greater long-term savings and a shorter payback period.
As you weigh up your options, get a quote from multiple solar installers. They can provide detailed assessments of your property’s solar potential and help you determine if a 5kW system is the right choice for your specific circumstances.
