It depends on on how many you get fitted and how much power you are using, to be honest. There is not really a set amount that you will save; if you only invest in a couple of solar panels, they will produce less energy than you would get with, say, ten solar panels. It also depends on where in NI you are based, as some places obviously get more sun than others.

For the best solar panels, NI residents should look to companies like First Class Solar. You can find them online (https://firstclasssolar.co.uk), and you can easily get some good deals to put together if you hire a company like that. Most of the time, they can give you a decent idea of the kind of savings you should expect to see if you invest in their solar panels.