With a standard SEAI application, you generally choose a registered heat pump contractor, arrange the required technical assessment, apply before work begins, and wait for approval before installing the system. You then submit the required completion documents, which may include a post-works BER assessment, for the grant to be processed. A One Stop Shop can manage much of this paperwork and coordinate the survey, installation and other energy upgrades, but it may use its own pricing and service arrangements. SEAI ultimately decides whether the application qualifies, so check the current process and conditions on the official SEAI website.