Heat Pump Warranty Claims + Disputes UK 2026

Manufacturer warranty (covers the unit):

• Compressor + heat exchanger: typically 5-10 years (Vaillant 7-year, Daikin 5-year, Mitsubishi 7-year, NIBE 10-year on heat exchanger).
• Other parts (pumps, sensors, controllers): typically 2 years.
• Labour: typically NOT covered after year 1 (you pay the installer to install warranty parts).
• Conditions: annual service by MCS-certified engineer to maintain warranty validity. Failure to register the unit within 90 days of install can void manufacturer warranty.

Installer workmanship warranty (covers the install):

• Typically 2-3 years on all install work (pipework, electrical, commissioning).
• Some installers offer 5-7 year extended workmanship warranty for premium fee.
• Covers: joint leaks, electrical safety, sizing errors (within reason), commissioning quality.
• Doesn't cover: performance vs quoted figures (separate dispute path), wear-and-tear, third-party damage.

MCS / TrustMark insurance-backed warranty (covers installer collapse):

• Automatic with BUS-eligible install - protects your workmanship warranty even if the installer goes out of business.
• Covers: rectification of poor workmanship that the original installer can no longer address.
• 2-year period from install completion typically.

1. Identify the issue precisely. Don't say 'heat pump broken'; say 'aux electric heater runs 40% of total cycles - SCOP dropped from 3.2 to 2.4 over the past 6 months'. Specific symptoms drive better diagnosis.
2. Document the issue: photograph any visible fault, screenshot manufacturer app data, save controller error codes. Send to installer in writing (email, not phone).
3. Contact installer first. This is their MCS obligation - they file with manufacturer on your behalf for unit-level issues. Request written confirmation of receipt.
4. Installer diagnostic visit. Get diagnosis IN WRITING - both the fault description + the recommended fix. Don't accept verbal 'we'll sort it'.
5. Wait for resolution timeline. Modern Insulation Code of Practice expects 28 days for routine repair; sooner for safety / total-failure issues. If exceeded, escalate.
6. Escalation if unresolved. Use the routes below based on dispute type.

1. 'Covered by manufacturer or installer?' grey area.

• Sensor failure 18 months after install: manufacturer says 'failed after the 12-month all-parts warranty period - your installer should fix as workmanship'. Installer says 'sensor failed mechanically - manufacturer issue, not workmanship'.
• Resolution: the MCS / TrustMark code of practice expects installer to file with manufacturer + cover installer labour while waiting. Push back on either party deflecting; escalate to TrustMark.

2. Workmanship issues only manifesting in cold weather (year 2-3).

• Pipework freeze damage during -8C cold snap = installer should have used adequate insulation. But installer warranty period typically expired.
• Resolution: if within 6 years of install, may be covered under Consumer Rights Act 2015 (durable + fit for purpose). For frost damage specifically, MCS standards apply for the install's lifetime.
• File claim citing CRA + MCS standards. Escalate via TrustMark if installer disputes.

3. SCOP underperformance vs installer's quoted figure.

• Installer quoted SCOP 3.8; actual measured SCOP 2.9.
• Resolution: performance commitments aren't covered by manufacturer or installer warranties directly - it's a Consumer Rights Act issue ("not fit for purpose"). MCS has heat-loss calc verification process.
• Submit MCS complaint citing the installer's quoted figure + actual measured data (manufacturer app screenshots over 12+ months).

1. TrustMark (workmanship + first-line dispute).

• UK Government-endorsed quality scheme for retrofits.
• File via TrustMark complaints process.
• Handles: poor workmanship, unfulfilled warranty obligations, installer collapse (insurance-backed coverage).
• Typical resolution timeline: 4-12 weeks.

2. MCS (design + commissioning).

• File complaint via MCS consumer complaints process.
• Handles: design errors (heat-loss calc, sizing), commissioning failures (WC curve, anti-Legionella), MCS certification breaches.
• Investigates installer + can revoke MCS certification for serious breaches.
• Timeline: 6-16 weeks.

3. Energy Ombudsman.

• Final escalation if TrustMark + MCS don't resolve.
• File via Energy Ombudsman.
• Independent decision binding on installer.
• Timeline: 12-26 weeks.

4. Citizens Advice + Trading Standards.

• Useful for: Consumer Rights Act 2015 issues (durable + fit for purpose), installer refusing to honour warranty, deceptive sales practices.
• Free advice + can escalate to Trading Standards for criminal investigation if needed.

5. Small Claims Court.

• Last resort for unresolved disputes under GBP 10,000.
• Court fees GBP 25-455 depending on claim value.
• Don't proceed without prior escalation through above routes.

1. Keep all written installer commitments. Quoted SCOP, WC curve, anti-Legionella schedule, aftercare visit promises. Email, not phone.
2. Get MCS install certificate after completion. Required for BUS claim AND warranty validation. Photograph + save in cloud storage.
3. Register manufacturer warranty within 90 days. Most manufacturers require online registration to activate full warranty - missing this can void coverage.
4. Document baseline performance. Take manufacturer app screenshots in first heating season showing SCOP, run-time, fault codes. Provides reference point for any future degradation claims.
5. Annual service by MCS engineer. Required to maintain warranty. Get written service report each year - documents condition + identifies issues early.
6. Photograph install completion. All visible install work, isolation switches, condensate drainage. Useful evidence for future workmanship disputes.