Certainly isn’t today. In the U.K. solar panels have about a 14 month payback, no incentives other Thant hey are currently tax free (like food. Electric from the grid has a 5% tax)

On top of that there’s an inverter, and if you can’t use all the power immediately you’d need a battery too, which tends to increase the cost.

The biggest cost though is installation.

I imagine the costs of purchasing and installing the panels in the UK are similar, but in Ireland there's definitely grants:

https://www.citizensinformation.ie/en/housing/housing-grants...

You do make a good point about VAT on electricity bills also being a factor in the break even calculation. In Ireland it's 9% and that's a temporary cost of living measure and will revert to 13.5% in 2030.