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How Many Solar Panels Do I Need?
July 29, 2025
If you’re thinking about investing in solar panels for your home, one of the first and most important questions you’ll ask is: how many panels do I need?
Solar isn’t a one-size-fits-all solution, and while online calculators can give a quick estimate, a proper understanding of the factors that can affect the sizing of your solar system will help you to make a smarter, more informed long-term investment.
In this article, we will look at how much energy the average household uses, and how to calculate your own requirement based on real-world conditions.
1. Why it Matters
Knowing how many solar panels you need is essential for:
• Budgeting: Solar PV systems are priced by kilowatt capacity.
• Roof planning: You may be limited by available space or shading.
• Grant applications: SEAI incentives are awarded based on system capacity.
• Return on investment: A well-sized system is more cost-effective long term.
Going too big can lead to unnecessary upfront costs, while going too small might not deliver the savings you’re hoping for.
The goal is to find a sweet spot between energy production, household demand, and physical constraints.
Reputable solar installers will visit your home to carry out a consultation to assess your energy needs and available space. From this they will create a customised system design, tailored to your home.
2. Understand your household energy usage
The foundation of any solar PV system is your household’s current electricity consumption. In Ireland, this is measured in kilowatt-hours (kWh) and is shown on your electricity bill.
National Averages
The average household in Ireland uses around 4,200 kWh of electricity per year (source: SEAI).
However, this varies depending on the size of your home, the number of occupants, and your lifestyle.
Typical Usage Breakdown:
| Household Type | Annual Usage (kWh) |
|---|---|
| 1–2 person apartment | 2,000 – 3,000 |
| 3–4 person semi-detached home | 3,500 – 5,000 |
| 5+ person detached home | 5,500 – 7,000+ |
Source: Central Statistics Office (CSO)
Note: Homes with heat pumps, electric vehicles (EVs), tumble dryers, or electric showers will typically have higher usage.
3. How much electricity can a solar panel produce in Ireland?
While Ireland doesn’t enjoy as many bright and sunny days as southern Europe, our long summer daylight hours and improving solar panel efficiency make solar PV a viable option.
1 kW of solar PV generates between 850 and 1,000 kWh per year in Ireland, depending on roof orientation, tilt, and shading (source: Get Solar Panels).
A single 430W solar panel (a common size in 2025) can generate between 365 and 430 kWh/year under Irish conditions.
This means that to generate 4,200 kWh annually (the average Irish home), you’d need between 10 and 12 high-efficiency panels.
4. Calculating how many panels you need
To calculate the number of panels you need:
Annual household energy use ÷ Annual output per panel = Number of panels needed
For example, if your home uses 4,200 kWh per year, and you choose 430W panels (each producing approximately 400 kWh a year)
4,200 ÷ 400 = 10.5 panels
In this case, you would need 10 or 11 panels to meet your home’s energy needs.
You can round up or down depending on the available roof space, budget, or if you’re considering future add-ons such as an electrical vehicle (EV) or heat pump.
5. Consider roof size and orientation
Once you know how many solar panels you need, the next step is to check if you roof can accommodate them, and if they are facing the right direction.
Space Requirements:
Modern solar panels are typically 1.8m x 1.1m or around 2m² per panel.
This means you need:
• Approximately 12m² available space for 6 panels
• Approximately 20m² available space for 10 panels
• Approximately 32m² available space for 16 panels
The space needs to be clear of obstructions such as chimneys, vents and skylights; and ideally not shaded during daylight hours.
Orientation Matters:
• South-facing roofs are ideal in Ireland.
• East- or west-facing roofs work well too, often with just 10–15% reduced output.
• North-facing roofs generally aren’t suitable for PV unless tilt-mount systems are used.
Read this article to learn more about the ins and outs of solar panel orientation.
6. Think beyond today’s usage
While many homeowners base their system size on their current electricity usage, it’s also worth asking:
• Will my electricity usage increase in the future?
• Am I planning to install a heat pump or EV charger down the line?
• Do I want to add battery storage later on?
In these cases, you may want to slightly oversize your system to futureproof your home’s energy needs. Irish energy policy is moving towards electrification of heating and transport, so planning ahead is an important consideration.
7. Understand battery storage
A solar battery allows you to store excess electricity generated during the day for use during periods of low daylight, or during the night.
This is particularly useful in Ireland because:
• Most homeowners are out of the house (at work or school) during peak generation hours.
• Without a battery, any unused electricity is exported back to the grid.
While you can receive payments for exported electricity under the Microgeneration Support Scheme (MSS), self-consumption is almost always more valuable then exporting, especially as daytime usage tends to be low in typical households.
Learn more about export energy and the Microgeneration Support Scheme (MSS).
8. Grants and regulations
The Sustainable Energy Authority of Ireland (SEAI) offers grants of up to €1,800 for home solar PV systems, which helps to offset installation costs.
Learn more about the SEAI Home Solar Grant and how to apply.
9. Real-world system examples
Here’s how system sizes compare for typical Irish homes:
| Household Type | Annual Usage (kWh) |
|---|---|
| 1–2 person apartment | 2,000 – 3,000 |
| 3–4 person semi-detached home | 3,500 – 5,000 |
| 5+ person detached home | 5,500 – 7,000+ |
10. Key takeaways
• The average Irish home needs around 10-12 panels (4-5 kWp system) to meet annual electricity needs.
• Roof orientation, size, and shading play a significant role in output.
• Battery storage, while optional, can improve self-sufficiency.
• Grants are available from SEAI and can significantly reduce upfront costs.
• Oversizing your system may make sense if you plan to electrify more of your home in the near future.
Final Thoughts
Solar PV is one of the most effective ways to take control of your home’s energy use, lower your electricity bills, and reduce your carbon footprint, but a properly designed system is key.
While rough estimates can be helpful, every home is different.
The best way to know exactly how many solar panels you need is to book a consultation and survey with a reputable, qualified solar installer. They will assess your roof, energy needs, usage patterns, and goals to design a system tailored to your home, ensuring you get the best possible return on your investment.
Curious How Many Solar Panels Your Home Might Need?
Every home is unique, and the right solar setup depends on a few key details.
If you’re considering solar and would like some expert guidance, we’re here to help.
Fill in the form below to arrange a free home consultation and survey.
We’ll take a look at your property and recommend a solar solution that’s tailored to your home, no pressure, just clear, helpful advice.