Brendan Quirke spent 14,000 euros on an air-source heat pump and found his heating bills barely changed. The contractor had installed the system correctly. The problem was the house itself, a 1960s semi-detached with minimal wall insulation and single-glazed windows in three rooms.

Heat pumps operate on a different principle than gas boilers. A gas boiler produces intense heat quickly, which compensates for a poorly insulated building. A heat pump produces lower-temperature heat consistently, which only works efficiently when the building retains that heat well.

Where the sequence breaks down

The standard advice from energy agencies recommends insulation first, then airtightness measures, then renewable heating systems. Most homeowners reverse this because a heat pump feels like the significant, visible action. Insulation feels unglamorous.

In Brendan's case, an energy assessor later estimated that adding external wall insulation and replacing those three windows would have reduced his heating demand by roughly 40%, meaning a smaller, cheaper heat pump would have been adequate. He had bought a system sized for a poorly performing building.

Grants do not change the logic

Irish government grants for heat pumps are currently structured in a way that can encourage installation before other retrofits. The grant exists regardless of the home's current energy rating. Accessing a grant for an upgrade that the house is not ready for is still a sequencing error, just a subsidised one.

The Building Energy Rating, or BER, is the starting point. An assessor charges around 150 to 250 euros for a full report and will identify exactly which measures should happen in which order.