Which is the best county for solar in Ireland? How location in Ireland affect solar output
Ireland's counties ranked best to worst for solar potential
Same panels, same system, different county. How much does it change the output?
Location does have an effect.
The sunny southeast lives up to its name, with solar installations there consistently leading the pack., with solar panels installed in Wexford producing 9.2% more than the national average. Solar panels in County Donegal would produce the lowest output, at 7.6% below the national average.
Below, you can see the annual solar generation for identical systems across Ireland, and how that compares to the national average of 884 kWh / kWp.
All the counties of Ireland compared for Solar output
| County | Annual Solar Generation per kWp of panels Based on south-facing roof, 30° pitch | Compared to national average 884 kWh / kWp |
|---|---|---|
| County Wexford | 965 kWh | +9.2% |
| County Waterford | 949 kWh | +7.4% |
| County Wicklow | 947 kWh | +7.1% |
| County Dublin | 915 kWh | +3.5% |
| County Carlow | 911 kWh | +3% |
| County Cork | 907 kWh | +2.6% |
| County Kilkenny | 905 kWh | +2.3% |
| County Kerry | 896 kWh | +1.3% |
| County Clare | 888 kWh | +0.5% |
| County Laois | 888 kWh | +0.4% |
| County Kildare | 885 kWh | +0.1% |
| County Meath | 885 kWh | +0.1% |
| County Galway | 886 kWh | +0.2% |
| County Tipperary | 884 kWh | -0.1% |
| County Louth | 881 kWh | -0.3% |
| County Offaly | 881 kWh | -0.3% |
| County Westmeath | 871 kWh | -1.5% |
| County Limerick | 869 kWh | -1.7% |
| County Roscommon | 867 kWh | -2% |
| County Longford | 854 kWh | -3.3% |
| County Sligo | 847 kWh | -4.2% |
| County Leitrim | 842 kWh | -4.7% |
| County Mayo | 841 kWh | -4.9% |
| County Monaghan | 841 kWh | -4.9% |
| County Cavan | 841 kWh | -4.8% |
| County Donegal | 817 kWh | -7.6% |
What do the numbers mean above?
kWp (kilowatt-peak) of panels
kWp is a measurement of the maximum theoretical output of an array of solar panels. Imagine you took a set of panels, and put them in perfect lab conditions. The power they would produce in those ideal conditions is the kWp rating.
This is the value most solar installations are quoted in. When someone says "I've a quote for a 4kW system", what that means is a 4 kWp system. Equally, if someone says "I'm getting 440w panels installed", it means those panels would produce 440w under ideal lab conditions.
In the real world here in Ireland we never quite get those perfect conditions. But, in the middle of a blue sky summer day, you can get to 90%-95% of this theoretical maximum.
Annual Solar Generation per kWp of panels
Here we are talking about the number of units of electricity you'd get per year from a 1kWp installation on your roof. 1 unit of electricity = 1 kWh (kilowatt-hour) of electricity.
How we did these calculations
- Roof facing due south
- Roof angle: 30 ° (which is typical for an average house)
- No shading
- We picked one representative town in each county as the exact location
What makes the difference?
Weather, latitude and altitude
How far north / south you are has an effect, with further south being more productive. But the local weather is also significant, notably the typical cloud cover.
Altitude does have an effect, but here in Ireland, the variation in altitude isn't significant enough to have a noticeable impact.
Local weather is surprisingly important
Cloud cover is the main driver here that brings variety across the country. Yes, temperature has an effect (cooler is better), but again there's not enough difference here in Ireland for that to be significant.
Solar Installations in Dublin (3.5% above the national average) and Wicklow (7.1% above the national average) are great examples of how their sunnier weather gives solar panels installed in those counties an extra boost.
They outperform counties like Cork (2.6% above national average) and Kerry (1.3% above national average), despite Dublin and Wicklow being further north.
The datasets used in such calculations have huge amounts of historical data, using things like satellite records of cloud cover, to try and predict the likely solar energy available at every location across the country. It's never spot on, but still, they are very impressive tools that are available and have a surprising amount of localisation built in.
More information
One of our favorite resources is the Global Solar Atlas, which provides highly detailed information on solar irradiance levels and much more for every inch of the country.
