How Many Solar Panels Are Needed to Generate 1000 kWh Per Month?

Switching to solar energy is a smart investment for UK homeowners, landlords, and commercial property owners looking to reduce electricity costs and reliance on the grid. 

In this guide, we’ll break down exactly how many solar panels are needed to generate 1000 kWh per month, with simple explanations, expert guidance, and UK-specific insights to help you make an informed decision.

How Many Solar Panels Do You Need to Generate 1000 kWh Electricity Per Month

You’ll need approximately 24 solar panels, each rated at 400W, to generate 1000 kWh of electricity per month in the UK.

However, the exact number can vary depending on several key factors:

• Regional sunlight variance and average peak sun hours per day
  
• Panel efficiency
• Roof orientation and tilt
  
• System losses and performance ratio

Basic Calculation: Number of Panels for 1000 kWh:

1. Monthly Usage to Daily Consumption:
   1000 kWh per month ÷ 30 days = 33.3 kWh per day
   
2. Estimate Daily Output per kW:
   With an average of 3.5 peak sun hours/day, a solar system produces:
   3.5 kWh per day per installed kW
   
3. System Size Needed:
   33.3 kWh ÷ 3.5 hours = ~9.5 kW system required
   
4. Number of Panels Required:
   9.5 kW ÷ 0.4 kW (400W panel) = 23.75 panels

Rounded up, you’ll need 24 solar panels to reliably meet a 1000 kWh monthly target under UK conditions.

This estimate assumes you're using 400W panels, one of the most commonly installed panel sizes in the UK today. 

But what if you’re using lower- or higher-wattage panels? The total number of solar panels you’ll need can vary slightly depending on the specific panel capacity you choose.

Let’s break down how many panels are needed to build a 9.5 kW solar system using different panel wattages.

How Many Panels Are Needed to Build a 9.5 kW Solar System?

Solar panels vary in wattage, but most modern residential panels range between 370W and 450W.

Here’s how many panels you’d need depending on the wattage of each panel:

So, you’ll typically need 22 to 26 solar panels to generate 1000 kWh per month, depending on the panel wattage and efficiency.

Roof Space Consideration

Each panel is approximately 1.7 m², so for a 9.5 kW system:

• 24 panels x 1.7 m² = ~40.8 m²

You’ll need roughly 40–45 m² of unshaded roof space, ideally south-facing with a tilt between 30–40° for optimal performance.

Need help choosing the right system? Use Eco Answers’ Quote Comparison Tool to get tailored quotes from vetted UK solar suppliers. It’s fast, free, and connects you to the best deals on the market.

What Factors Affect the Number of Solar Panels You will Need for 1000 kWh per month?

Several key factors affect the number of solar panels you will need to generate 1000 kWh per month. These include:

1. Regional Sunlight Variance

Where you live in the UK has a significant impact on how many solar panels you’ll need to generate 1000 kWh per month. 

This is because different regions receive varying amounts of sunlight, specifically peak sun hours, which refer to the number of hours per day when sunlight intensity is strong enough to produce the panel’s maximum rated output.

Average Peak Sun Hours & Solar System Size Needed:

• South of England: Areas such as Cornwall, Devon, and the South East can receive around 3.8 to 4.2 peak sun hours per day on average throughout the year. These regions tend to have more favourable solar conditions, meaning your system will generate more electricity with fewer panels.
  
  For example, homeowners in Brighton or Bristol may meet their 1000 kWh/month target with a slightly smaller system or have higher excess generation during sunnier months.
  
  
• Midlands and Central UK: Cities like Birmingham, Leicester, and Nottingham receive slightly less, around 3.2 to 3.5 peak sun hours daily. While still suitable for solar, you may need to stick close to the full 9.5 kW system size to hit 1000 kWh monthly, especially if your roof has suboptimal orientation or partial shading.
  
  
• North of England & Scotland: In places such as Newcastle, Glasgow, or Inverness, average peak sun hours drop to around 2.5 to 3.2 hours per day.
  
  This means systems in these areas are less productive overall, either producing slightly less than 1000 kWh per month or requiring a larger system (more panels or higher-efficiency panels) to meet the same output.
  
  Seasonal variation is also more noticeable here, with lower output during the winter months and higher generation during summer.

The difference in sunlight hours doesn’t mean solar panels aren’t worth it in the North, it just means your system may need to be better optimised. This could include:

• Using higher-efficiency panels (e.g. 420W–450W)
  
• Installing battery storage to maximise usage of generated power
  
• Installing panels at a steeper tilt to better capture low-angle sunlight in winter

According to the Energy Saving Trust, even homes in Scotland can generate over 3,000 kWh per year with a well-placed 4 kW system, proving solar viability across the UK.

2. Panel Efficiency and Type

Monocrystalline panels are more efficient and require less space than polycrystalline panels. Premium brands can produce more electricity in the same footprint. We’ve covered the differences in detail in our guide comparing monocrystalline and polycrystalline solar panels.

High-efficiency panels (20–23%) like those from SunPower or REC will require less space. Lower-efficiency panels will require more to hit 1000 kWh.

Insights: Check out our guide on the most efficient solar panels on the market to help you make an informed decision.

3. Roof Orientation and Tilt

The direction your roof faces and its angle (tilt) have a direct impact on how efficiently your solar panels can convert sunlight into usable electricity. These physical characteristics determine how much sunlight your panels are exposed to throughout the day and year.

Optimal Orientation:

• In the UK, the ideal orientation is a south-facing roof, as it captures the most consistent sunlight from sunrise to sunset.
  
• A tilt angle of 30° to 40° is considered optimal. This range matches the sun's average position in the sky over the course of the year, maximising generation during spring, summer, and autumn.

East- and West-Facing Roofs:

• If your roof faces east or west, it will still receive sufficient sunlight to make solar worthwhile, especially with modern, high-efficiency panels.
  
• However, production will be more concentrated in the morning (east-facing) or afternoon (west-facing) and overall generation will be around 15–20% lower than a south-facing system.
  
• To compensate for this reduction, you may need to increase your system size by 2–4 additional panels to reach the same monthly target of 1000 kWh.

North-Facing Roofs:

• North-facing roofs are generally not ideal for solar in the UK, as they receive significantly less direct sunlight.
  
• In some cases, it may still be viable if you use specialist mounting brackets to adjust panel angle, or if you're supplementing with ground-mounted panels in a suitable location.

What If Your Roof Isn’t Perfect?

Even if your roof isn’t perfectly aligned:

• You can use tilt brackets to improve panel angle on flat or shallow-pitched roofs.
  
• Split-array installations (e.g. some panels east-facing, some west-facing) can help balance generation throughout the day.
  
• Inverter selection becomes important, installing dual MPPT (Maximum Power Point Tracking) inverters allows the system to manage uneven sun exposure more efficiently.

4. System Losses and Performance Ratio

While solar panels are rated for ideal laboratory conditions, real-world systems never operate at 100% efficiency. Various factors reduce how much of the sun's energy is actually converted into usable electricity for your home or property.

What Are System Losses?

According to Ofgem, most UK solar PV systems experience 10% to 20% energy loss, primarily due to:

• Inverter losses: Converting DC electricity (produced by the panels) into AC power (used by your appliances) typically results in a 5–8% loss.
  
• Temperature losses: Solar panels work more efficiently in cooler climates, but during hotter days, especially on dark rooftops, panels can lose 3–5% output due to overheating. Read our article on how solar panels perform under extreme heat to understand their efficiency in high-temperature conditions.
  
• Dust and dirt: Accumulation of debris on panels can block sunlight. While UK rain helps clean panels naturally, mild losses still occur.
  
• Cable and connection losses: Electrical resistance in the system’s wiring results in small but consistent losses, especially in poorly installed systems.
  
• Shading: Even partial shading on one panel (from chimneys or trees) can affect the output of the entire string if not properly managed with optimisers or microinverters.

What Is the Performance Ratio?

The Performance Ratio (PR) is a measure of your system's actual output versus its theoretical maximum, essentially, how “well” your system is performing under local conditions. It accounts for all the losses mentioned above.

• A PR of 100% means perfect efficiency (which isn’t realistic).
  
• In the UK, a typical residential solar system has a PR of 80–90%, which is considered very healthy for our climate and technology standards.
  
• Well-installed systems using quality components and optimised designs tend to achieve PRs closer to the 90% mark.

Why This Matters:

Understanding system losses and performance ratio is crucial because it impacts how many panels you’ll need. If your system has a lower PR, you'll require a slightly larger system (i.e. more panels or higher output per panel) to reliably generate 1000 kWh per month.

Tip: Ask your installer for an estimate of your system's expected performance ratio. This should be included in your solar performance modelling or quotation.

Can Your Roof Support a 9.5 kW System?

A 9.5 kW solar PV system is larger than what most standard UK homes currently install. The typical residential system ranges between 3 kW and 6 kW, designed to offset average usage of 250–350 kWh per month. 

However, if your household uses around 1000 kWh per month, which is well above average, a system of this size is both practical and necessary.

To support a 9.5 kW system, your roof will need to accommodate approximately 24 solar panels rated at 400W each. That equates to about 40–45 m² of usable roof space, assuming minimal shading and good orientation.

What if I don't have enough roof space for a 9.5 kW system?

If you're concerned your roof may not have the available space or the ideal tilt and orientation, there are several smart workarounds:

• Use higher-efficiency panels (e.g. 430W–450W) to generate more power from fewer panels.
  
• Install a battery storage system to make the most of the solar you do generate, storing excess for evening or nighttime use.
  
• Opt for a split-array design that places panels on multiple roof sections (e.g. east- and west-facing).
  
• Consider ground-mounted systems or solar carports if you have available land or driveway space, particularly useful for rural properties or commercial premises.

How Much Will a 24-Panel System Cost in the UK?

The cost of solar panels vary depending on equipment, brand, and installer.

You may be eligible for 0% VAT on solar installations under the UK government's green energy scheme.

How Much Will You Save With 1000 kWh of Solar Per Month?

Assuming the average electricity cost in the UK is ~28p/kWh (Ofgem, 2025 price cap), generating 1000 kWh saves:

1000 x £0.28 = £280/month
Annual savings = £3,360

This doesn’t include Smart Export Guarantee (SEG) payments for selling excess electricity back to the grid.

What Type of Property Can Benefit From a 1000 kWh/Month Solar System?

Homeowners

• According to Ofgem, a typical UK household uses 2900–4000 kWh per year.
  
• If you're using 1000 kWh per month, your energy needs are well above average, likely due to electric heating, EV charging, or large households.

Landlords

Solar can lower energy bills and improve EPC ratings, a major plus for rental properties. Properties with multiple flats or HMOs may benefit from a shared system.

Commercial Buildings

Shops, offices, and small factories often consume more than 10,000 kWh/year. A 1000 kWh/month system can supplement daytime energy use, reducing overheads and helping with ESG compliance.

Is a Battery Storage System Worth It?

If you’re rarely at home during the day, much of the solar energy generated could go unused unless you have a way to store it.

Benefits of Adding Battery Storage:

• Use solar power in the evening.
  
• Reduce grid dependency.
  
• Increase self-consumption from ~30% to ~70%.

A typical battery (5–10 kWh) adds £3,000–£6,000 to installation costs. Take a look at our solar battery cost guide for a more comprehensive understanding.

Solar Panels Grants and Financial Incentives for UK Homeowners

While the Feed-in Tariff has ended, there are still benefits and support available:

• 0% VAT on solar panel installations until March 2027.
• Smart Export Guarantee (SEG) to earn from excess generation.
• ECO4 Scheme and Home Upgrade Grant for low-income households.

Get Personalised Solar Panel Quotes with Eco Answers

Every property is different, and getting an accurate estimate is essential. That’s where Eco Answers can help.

Use their free, easy-to-use quote comparison tool to:

• Receive quotes from trusted UK suppliers
• Compare prices, products, and warranties
• Save time and find the best deal tailored to your needs

Get your free solar quote today, no obligation, just competitive offers from vetted installers.

FAQs

How long will a 9.5 kW solar system last?

Most solar panel systems last 25 to 30 years, with warranties typically covering 20-25 years for panels and 5-10 years for inverters.

Can I install solar panels if I rent or own a flat?

If you're a landlord or tenant, you’ll need permission from the property owner. For flats, options are limited unless the building supports a communal system.

Will I still get electricity on cloudy days?

Yes. Solar panels still produce electricity under cloud cover, just at reduced efficiency. Modern systems are designed to work in the UK climate.

Final Thoughts

To produce 1,000 kWh of electricity per month, most UK homes and commercial buildings require a 9.5 kW solar panel system, typically made up of around 24 panels rated at 400W each.

Your specific requirement depends on location, panel efficiency, and available roof space.

High energy users can see significant long-term savings and improved energy independence. Whether you're a homeowner, landlord, or property manager, now is a great time to explore your solar options.

Let Eco Answers connect you with the right solar installer using their free quote comparison tool, it’s fast, simple, and tailored to your needs.