Location does have an effect.
The sunny south-east lives up to it's name with a solar installation there at the top of the leader board, 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.
|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%|
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 perfect 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 435w panels installed", then those panels would produce 435w in perfect 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.
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 far north / south you are has an effect, with further south being more productive. But also the local weather is significant, too, notably the typical cloud cover.
Altitude also has an effect, but here in Ireland we don't have enough variation in altitude for the effects to be significant.
Cloud cover is the main driver here that bring 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 national average) and Wicklow (7.1% above national average) are great examples of how their sunnier weather gives solar panels installed in those counties any extra boost.
They out perform 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 doing such calculations have huge amounts of historical data in, 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 that have a surprising amount of localization built in.
One of our favourite resources here is the Global Solar Atlas, where you can see huge detail in solar irradiance levels and much much more across every inch of the country.
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