What Size Solar Panel System Does Your Home Need?
Choosing the right solar panel system for your home isn’t just about picking panels off the shelf — it’s about matching your energy needs, roof space, and future plans with a system that pays for itself and then some. Whether you’ve seen mentions of 200W or 400W panels or you’re wondering how many solar panels your roof can actually hold, this guide will help you make sense of it all.
Scottish homes in particular need a smart, tailored approach. From cloudy skies to varied roof styles, there's no one-size-fits-all answer — but by the end of this article, you’ll be well on your way to understanding what’s right for your home.
How Much Energy Does Your Home Use?
Your solar panel system should match — or closely offset — your annual energy usage. Here’s how to check and compare:
Step 1: Look at your latest electricity bill for the figure listed as "kWh used."
Step 2: Multiply that by 12 to get your annual estimate.
To help guide you, here are typical energy usage levels for different household types in Scotland according to Ofgem:
| Energy Use | Example – home type and number of residents | Typical annual gas use (kWh) | Typical annual electricity use (kWh) | Typical annual electricity use (multi-rate, such as Economy 7) (kWh) |
|---|---|---|---|---|
| Low | Flat or 1-bedroom house; 1 to 2 people | 7,500 | 1,800 | 2,200 |
| Medium | 2–3 bedroom house; 2 to 3 people | 11,500 | 2,700 | 3,900 |
| High | 4+ bedroom home; 4 to 5 people | 17,000 | 4,100 | 6,700 |
Keep in mind:
Winter usage is often higher due to lighting and heating.
Homes with electric heating, hot tubs, or EV chargers will naturally use more.
Understanding Solar Panel Sizes & Power Ratings
Solar panels are often described in terms of wattage (how much power they generate under ideal conditions) and physical dimensions (which determine how many you can fit on your roof).
Here’s a breakdown of typical options available in the UK:
| Panel Wattage | Dimensions (mm) | Use Case |
|---|---|---|
| 50W | ~500 x 670 | Portable/off-grid/caravans |
| 200W | ~1485 x 670 | Small off-grid setups |
| 400W+ | ~1722 x 1134 | Standard UK residential roofs |
For homeowners, modern panels between 380W–450W are the most common and efficient choice.
Quick Guide — Common System Sizes and What They Power
To give you an idea of what different system sizes can support, here’s a quick guide:
| System Size | Annual Output (Approx.) | Suitable For |
|---|---|---|
| 3kW | ~2,600–2,900 kWh | 1–2 person home, no EV |
| 4kW | ~3,400–3,800 kWh | Small family, occasional high-energy use |
| 6kW | ~5,000–6,000 kWh | Large family, EV charger, battery storage |
This will vary depending on your location, roof pitch, and shading. But it’s a good baseline for understanding scale.
How Many Panels Will Fit on Your Roof?
This is where wattage and dimensions come into play. Here’s a rough guide:
| System Size | Panel Wattage | Panels Needed | Roof Area Required (m²) |
|---|---|---|---|
| 3kW | 400W | 8 | ~14.5 |
| 4kW | 420W | 10 | ~18 |
| 6kW | 420W | 14–16 | ~25–29 |
For an average Scottish semi-detached roof (20–30 m² of usable space), a 3–4kW system will usually fit without issues. Larger systems may require both roof faces or ground mounting.
Why Solar Panel Size Matters for Your Home
Getting the size right is crucial:
Under-sizing means you’ll miss out on savings.
Over-sizing could mean unnecessary costs, especially if you can’t use or store the extra electricity.
Panel efficiency varies — high-efficiency panels can produce more in less space, useful for small or shaded roofs.
In Scotland, where weather and light levels fluctuate, optimising for usable generation rather than just peak output is key.
Factors That Influence Your Ideal System Size
Every home is different, but these are the main factors that affect sizing:
Roof Orientation & Shading
South-facing roofs get the best exposure. East/west can still work, especially with battery backup.
Panel Type
Monocrystalline panels are more efficient than polycrystalline, making them better for compact roofs. Learn more in our guide: Which Solar Panel Is Best?
Battery Storage
Adding a battery allows you to store excess power instead of exporting it. If you're home in the evenings, this boosts savings.
EV Charging
If you own or plan to own an electric vehicle, a slightly larger system will help offset charging costs.
Futureproofing
Consider your plans. Adding a home office, heat pump or growing family? Slightly oversizing now could save on upgrades later.
Real-World Example: Paisley 6.72 kW Solar PV + Battery System
To see it in action, here’s one of our client installations:
Location: Paisley
Installed: July 2024
System: 16 × 420 W panels (6.72 kW) with a GivEnergy hybrid inverter
Battery: 2 × 5.2 kWh = 10.4 kWh
Estimated annual generation: ~6,700 kWh
Self-consumption: ~85–90% (~6,000 kWh used onsite)
Grid export: ~750 kWh/year
Annual savings: ~£1,800
Export income (SEG): ~£90
Payback period: 6–7 years
Lifetime savings estimate: £35,000+ over 25 years
This setup covers nearly all of the household’s energy needs — even with EV charging and electric heating.
Don’t Guess – Get a Custom Quote
There’s no need to rely on guesswork. At Thermal Care Scotland, we use industry-standard MCS calculators and detailed roof scans to recommend the perfect system for your home.
Whether you’re ready to go solar or just curious about what’s possible, we’re here to help.