SEAI Energy grants

I recently came across a paradox that a plumber would raise his prices for the amount of SEAI energy grant which makes obtaining a grant useless. Even more, my VAT bill will be higher to the portion of this increase.
Plumber claims that too much paperwork involved (for him) and process of getting paid is delayed and insists no grant should be requested.

Is it common with other plumbers?

These grants insist on traceability of payments to bring everybody into the tax system which is ultimately good for the economy.
If you have no paperwork it is difficult to get after service.

If a plumber charges VAT on the full amount of works I don't understand why it is a problem for him with traceability?!

There's also the plausibility that the plumber you're dealing with isn't registered, or have had their registration terminated due to their work falling below the standards required.

I'd advise seeking out a few alternatives and get their views.