4 kW Solar system – why are they still popular?

A 4 kW solar sytem can be a good option for a household with average energy consumption.
4kW solar systems are generally more affordable, produce as much electricity as the average household uses per year and will fit onto most roofs. However, If you have enough roof space, a 4 kW solar system might not be the best choice for your home now that exporting solar generation is so attractive, given the low marginal cost of adding additonal panels, even if your electricity usage is lower. By following poor advice regarding maximum system sizes and output limits, you could cost yourself £000’s without knowing it.
Compare the cost & savings of a 4kW Solar system below to other solar system sizes.
System sizeCostAnnual generationLifetime savingsNet savingsDifference in savings
4.38 kW£80704298 kWh£22,831£14,761£0
5.11 kW£83674912 kWh£24,259£15,892+£1131
6.57 kW£89635898 kWh£26,505£17,542+£2781
7.3 kW£92606310 kWh£27,425£18,165+£3404
Negative electricity bills

Generating more energy than you use could turn your electricity bills negative – like the customers below.

The marginal cost of adding panels to a 4 kW solar system is negligible, you may as well use the space available and go larger.

History of a 4kW Solar system.

Why is a 4kW solar system such a popular option? To answer this question, we must look back to when the Feed-in Tariff was first introduced. The highest level of support under the old Feed-in Tariff subsidy was in the 0-4kW band. At the time, solar panel sizes maxed out at roughly 250W per panel, which made it nice and simple as 16 panels x 250W = 4 kW solar system.

Therefore, the largest system often sold to residential customers would be a 4kW solar system as it didn’t make financial sense to go any larger and have the subsidy rate cut in half.

Today, modern panels of similar size go up to 400W, a 16-panel system today would be 6.4 kW.

As the Feed-in Tariff subsidy came to an end in 2019 and is no longer needed, there is no reason why you should limit yourself to installing a small 4kW solar system.

Take control of your energy supply
When should I install a 4 kW solar system?
  • If you have limited roof space where the maximum amounts to 10 panels or 4kW.
  • Budget constraints – a 4kW solar system will allow you to install a cheaper inverter as there is less power to handle and less panels are needed.

It will always be more cost-effective to go for a larger system as the marginal cost of adding a panel to the installation is much lower. You’ll also generate more energy.

Why are 4 kW solar systems still so popular?
  • The public is much more familiar with a 4 kW solar system – it’s much easier to sell something that a customer is already familiar with.
  • Productisation – creating a standard offering for your salespeople to sell.
  • 4 kW solar system capacity is often confused with the grid’s 3.68 kW AC output limit, the two are unrelated and shouldn’t be mixed up but they often are.
  • You can use a cheaper inverter as there is less power being generated/converted and no AC clipping (when DC generation exceeds the AC rated output of the inverter, the power is ‘clipped’ either the inverter uses the Maximum Power Point Trackers to lower the Wattage or the power is lost as heat).
Is a 4kW solar system the maximum size for homes? What is the 3.68 kW grid limit?

3.68 kW is the AC output limit per phase before permission is required from the DNO (District Network Operator). The goal should be to maximise the amount of time your solar panel system’s inverter is outputting 3.68 kWh.

A 4 kW solar system’s inverter will output 3.68 kWh when irradiation (light) is above 920Wh/m2.

A 7 kW solar system’s inverter will output 3.68 kWh when irradiation is above 525Wh/m2.

To maximise the output when not seeking permission and where roof space is not limited, a Huawei hybrid inverter combined with Huawei optimisers on each panel can handle a 10 kW solar system.
A 10 kW solar system’s inverter will output 3.68kWh when irradiation is above 368Wh/m2.

The average irradiance in the UK is 101Wh/m2.

Sacrificing some generation through AC clipping during the middle of the day in summer months, when irradiation is at its highest, during this time generation is likely to exceed usage anyway, to maximise production throughout the rest of the year (90% of daylight hours) when generation will likely be more useful is the advice that we would give to everyone considering installing a 4 kW solar system.

Unless you have limited roof space a 4 kW solar system is unlikely to be the best choice for your home. By following bad advice regarding system sizes and output limits, you could cost yourself £000’s. A 4kW solar system price would then not be so affordable.

How many panels in a 4kw solar system?

In a 4kW solar system, the number of panels required depends on several factors, including the wattage of the individual solar panels and their efficiency. To determine the number of panels, we must consider the system’s total capacity (4kW) and the average wattage of the solar panels available at the time of installation.

For example, if we assume each solar panel has an average wattage of 300W, we can calculate the number of panels needed by dividing the total capacity (4kW) by the wattage per panel (300W).

Number of panels = 4,000W ÷ 300W ≈ 13.33

Since you cannot have a fraction of a solar panel, you would need to round up to the nearest whole number. Therefore, a 4kW solar system using 300W solar panels would require approximately 14 panels.

It’s important to note that the actual number of panels may vary depending on factors like the geographic location, orientation, and shading at the installation site. A professional solar installer like Leoht can provide a more precise estimate based on these factors.

How much electricity does a 4kw solar system produce per day?

The amount of electricity a 4kW solar system produces per day depends on various factors such as location, weather conditions, and the orientation of the solar panels. On average, a 4kW solar system can generate around 16-20 kilowatt-hours (kWh) of electricity per day.

Solar panels operate at peak efficiency during clear, sunny days when they receive direct sunlight. However, on cloudy or overcast days, their output may be lower. Additionally, the angle and direction the panels are installed can affect their daily production.

To get a more precise estimate of how much electricity a 4kW solar system would produce in your specific location, you can use solar calculators or consult with a professional solar installer like Leoht. They can consider local weather patterns and other variables to give you a more accurate daily production estimate for your solar system.

faq’s about solar panel systems

One for the zoom family quiz!

In 1921, Albert Einstein won his first and only Nobel prize for his work on describing the photoelectric effect.

In a nutshell, light (a beam of particles) knocks off electrons from the solar cell; the solar cells direct these electrons along a current – creating electricity. In theory, solar panels could last forever as there are no moving parts.

 

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Solar power panel efficiency has increased significantly over the last ten years so you might be surprised at how much electricity even a small roof could generate.

The smallest system we would recommend would be 9 x 380W panels, covering an area of 17 square meters. (4m x 4.25m).

 

How many solar panels do I need?

No. It’s a common myth. Whilst south facing is the most optimum facing position, as a rule of thumb – an identical East or West facing roof would generate 85% as much energy as the south-facing roof.

You may prefer to have an east and west facing roof than the south and north-facing roof as you could fit twice as many electric residential solar panels on the east/west roof than just south facing.

Even a North facing roof will generate approx 55% as much energy as a south-facing roof. For example, a 20 year old 10% efficient south-facing solar panel would generate approximately the same amount of energy as a modern north-facing solar panel.

 

How do solar panels generate electricity

The installation of solar panels on residential buildings are considered permitted development so you do not require planning permission if they comply with the following conditions.

There are necessary limits and conditions which must be complied with to benefit from permitted development rights.

  • Solar panels should not be installed above the highest part of the roof and should not project more than 200mm from the roof slope or wall surface.
  • Installers should not install solar panels on a building that is within the grounds of a listed building or on a site designated as a scheduled monument.
  • If your property is in a conservation area, or a World Heritage Site, you must not install solar panels on a wall that faces a highway.

Feel free to reach out to us to buy solar panels in the UK & switch to a sustainable lifestyle. Give us a call at 01273 286 627 and request for a free design and quote.

 

Planning Portal

The district network operator (DNO) is the company responsible for distributing electricity from the national grid to your home. Installers must inform the DNO of your installation within 28 days after the date of installation. Leoht will handle this for you.

You do not require permission for systems under 16 amps per phase (3.68kW single-phase or 11.04kW three-phase supply). All of the residential solar panel systems that we install fall into this category. System sizes are based on the AC inverter rating rather than the peak DC output of the solar system.

“By following bad advice regarding output limits you could be costing yourself £000’s.”

 

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Not on their own. But it is possible when combined with a time of use tariff and energy storage – depending on the time of use tariff and smart export guarantee rates.

For example, Octopus Go tariff pays 5.5p/kWh for every unit exported and charges 5p/kWh for off-peak use from 00:30 – 04:30. You could install solar panels that generate the equivalent of 100%+ of your electricity consumption and earn 5.5p/kWh for every unit exported to pay for topping up the batteries in the winter at 5p/kWh.

Your bills could even go negative if you can generate more than you use!

Time of use tariffs are why we have smart meters so expect them to become more common in future.

Yes. Solar panels are worth the cost. We believe that solar pv panels systems are an excellent investment for both you and the environment.

Our solar power panels systems cost between £5000 to £9000+ VAT, depending on the size and location of your home. This may seem expensive, but by installing a solar system we aim to reduce your electricity bill by up to 100%. Where else could you earn 9-13% per year tax-free on a low-risk investment, whilst protecting against rising energy prices and helping the environment at the same time.

Our solar panels are durable and come with a 25-30 year warranty. If well maintained, our solar panels can last for more than 30 years. Our solar panels are modern and blend well with any roof. A premium solar panel installation acting as your home’s own energy supply is likely to increase the value of your property.

Solar panels are largely maintenance-free. Over time, however, they may be affected by environmental factors – dead leaves, for example, may block sections of the panel. We recommend that solar panels are checked every few years to ensure maximum efficiency and cleaned once or twice a year.

Solar panels need sunlight to generate energy, so they do not work at night. However, you can install a battery to store excess electricity generation during the day to then be used later at night.

Negative electricity bills

Generating more energy than you use could turn your electricity bills negative.

The marginal cost of adding panels to a 4 kW solar system is negligible, you may as well use the space available and go larger.

Find out how much you could save with solar

Our cost and savings calculator can help you find the right solar specification for you and how much you could save!

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