From April 1, 2022 to December 31, 2023, the reduced rate of 6% VAT will also apply to the supply and installation of solar panels, solar water heaters and heat pumps in homes younger than 10 years. New-build homes and homes erected after demolition are now also eligible. For homes older than 10 years, the reduced rate of 6% already applied and this regulation will remain unchanged.
Source Vandelanotte