Answer first
Repair is usually stronger when the fault is isolated, parts are available, the wider design remains suitable and the cost is proportionate to remaining service life. Replacement deserves consideration when faults repeat, a major part is unavailable or expensive, capacity is wrong, refrigerant or controls are obsolete, or the entire system needs redesign.
Compare written repair and replacement scopes. Include warranty, labour, downtime, efficiency, required radiator or electrical changes and whether replacement solves the root cause.
Confirm the fault before pricing a new system
View sourceReplacement should recheck heat loss, emitters and controls
View sourceCurrent Scottish funding treats replacement heat pumps separately
View sourceGet a diagnosis before choosing repair or replacement
Share the make, model, postcode and what the system is doing. FLO can route the enquiry to the right service, diagnostic or replacement conversation.
Confirm what actually failed
Controls, sensors, water flow, valves, pumps, power supply and installation defects can mimic an outdoor-unit failure. A model-specific diagnostic should identify evidence before parts are ordered.
Ask whether the proposed component is confirmed, suspected or being tried. If uncertainty remains, agree the next test and spending limit.
Assess the wider system condition
A sound heat pump connected to undersized emitters or dirty, restricted pipework will still underperform. Conversely, a good distribution system can make appliance replacement straightforward.
Review design capacity, flow temperature, annual electricity, fault history, cylinder and controls so the decision fixes causes rather than symptoms.
Compare risk as well as price
Repair price includes part, labour, refrigerant if applicable, access and warranty on the work. Replacement includes survey, removal, adaptation, commissioning, certification and new warranties.
Parts availability, expected downtime and temporary heating matter in winter or for vulnerable occupants. Put them beside the totals.
Check funding before assuming support
Home Energy Scotland’s current terms list replacement heat-pump funding separately and on a case-by-case basis. Do not assume the standard new-installation grant applies.
Obtain the diagnosis and proposed scope, then check current eligibility before work begins. A rushed replacement can make an otherwise eligible application invalid.
What to read next
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Questions people also ask
Is an old heat pump automatically inefficient?+
No. Measure behaviour and condition; age alone does not prove poor performance.
Should a compressor fault mean replacement?+
It is a major decision, but warranty, part availability, labour, system age and wider design all matter.
Can I get a grant to replace an existing heat pump?+
Current Scottish terms treat replacements separately and case by case; confirm before committing.
Evidence used for this answer
Figures are explained in context and links go to the independent source. Prices, tariffs, scheme rules and standards can change, so check the source again before making a financial or technical decision.
- MCS domestic heat-pump guideConsumer guidance covering design, installation, controls, handover and maintenance.
- MCS heat-pump design standardTechnical requirements for heat loss, equipment selection, domestic hot water and system design.
- Home Energy Scotland Grant and Loan: terms and eligible costsCurrent Scottish grant and loan limits, eligible heat-pump costs, application conditions and rural uplift rules.
- Energy Saving Trust: heat-pump questions answeredIndependent answers on servicing, maintenance and common household heat-pump decisions, including a current typical service-cost guide.