Article Content
Why System Size Matters
Choosing the right solar system size is arguably the most important decision in your solar journey. Too small, and you'll leave potential savings on the table. Too large, and you'll be paying for capacity you don't fully utilise. The sweet spot depends on your roof space, electricity consumption, budget, and whether you plan to add battery storage or an EV charger.
System Size Comparison
4kWp System (10–12 panels)
- Typical cost: €4,500–€6,500 (€2,700–€4,700 after SEAI grant)
- Annual generation: 3,400–3,900 kWh
- Roof space required: Approximately 20–25 square metres
- Best for: Average family homes (3–4 bedrooms), couples, smaller households
- Annual savings: €500–€800
- Payback period: 5–7 years
The 4kWp system is the most popular choice for Irish homes and for good reason. It provides an excellent balance of cost and output, covering 70–85% of a typical household's annual electricity consumption. It fits comfortably on most standard roof pitches and requires a relatively modest investment.
6kWp System (14–16 panels)
- Typical cost: €6,500–€9,000 (€4,700–€7,200 after SEAI grant)
- Annual generation: 5,000–5,800 kWh
- Roof space required: Approximately 30–35 square metres
- Best for: Larger homes, homes with electric heating or heat pumps, families with high consumption
- Annual savings: €750–€1,100
- Payback period: 5–7 years
The 6kWp system is ideal for households with above-average electricity consumption. If you have electric heating, a heat pump, an EV, or simply a larger family, the extra panels generate significantly more electricity without a proportional increase in cost (because the SEAI grant is capped at €1,800 regardless of system size).
8kWp System (18–22 panels)
- Typical cost: €8,500–€12,000 (€6,700–€10,200 after SEAI grant)
- Annual generation: 6,800–7,800 kWh
- Roof space required: Approximately 40–45 square metres
- Best for: Properties with very high electricity demand, home offices, combined solar + EV + battery setups
- Annual savings: €1,000–€1,500
- Payback period: 6–8 years
The 8kWp system is for households that know they have significant electricity needs — either now or in the future. If you're planning to get an EV, add battery storage, or your household has electric heating, the 8kWp system provides the headroom to meet these demands while still exporting surplus to the grid.
How to Choose the Right Size
The best way to determine your ideal system size is to look at your annual electricity consumption (found on your electricity bill or through your supplier's online portal). As a general guide:
- Consumption under 3,500 kWh/year → 4kWp system
- Consumption 3,500–5,500 kWh/year → 6kWp system
- Consumption over 5,500 kWh/year → 8kWp system
We always recommend a free site survey where we'll analyse your specific consumption patterns and roof characteristics before making a recommendation.
Frequently Asked Questions
What size solar system do I need for my home?
For an average Irish home consuming 4,200 kWh/year, a 4kWp system is ideal. Larger homes or those with electric heating may benefit from a 6kWp or 8kWp system.
How many solar panels do I need?
A 4kWp system needs 10–12 panels, a 6kWp system needs 14–16 panels, and an 8kWp system needs 18–22 panels.
Is a bigger solar system always better?
Not always. The SEAI grant caps at €1,800 regardless of size, so larger systems have higher net costs. Choose based on your actual consumption and roof space.