Frequently Asked Questions

Yes — completely free, with no catch. You complete the assessment online, receive your traffic light health indicators immediately, and there is no obligation to book a visit or pay anything. If you choose to book an engineer visit, the price is fixed and shown upfront. No account is required, no payment details are collected, and there is no follow-up sales call.

GreenWave produces four traffic light indicators based on your assessment answers: Comfort (heating performance — do rooms reach temperature?), Hot Water (DHW availability and performance), Running Cost Signals (indicators of poor efficiency — high bills, short cycling), and Controls & System Behaviour (fault codes, unusual behaviour, pressure issues). Green means no obvious concern was reported. Amber means the area is worth checking. Red means priority review is recommended. Grey means the area cannot be assessed from a form alone and requires on-site measured readings.

GreenWave works with all major brands installed in Ireland: Samsung, Daikin, Mitsubishi, LG, Hitachi, Vaillant, NIBE, Grant, Panasonic, and Hisense. Our engineer workflow includes manufacturer-specific controller navigation steps for each brand, so the guidance is always specific to your system.

The free online assessment is available to all homeowners across Ireland with no geographic restriction. Engineer visits are currently available in Dublin, Kildare, Meath, Wicklow, Wexford, Cork, Galway, Limerick, Waterford and surrounding counties. Coverage is expanding — check availability in your area by completing the free assessment and entering your eircode.

The clearest signs of poor heat pump efficiency are: electricity bills that are higher than expected for the heating provided, rooms that don't reach the desired temperature despite the system running for long periods, the system turning on and off frequently (short cycling), hot water that runs out or never reaches the right temperature, and high delta-T (a large difference between flow and return temperature). GreenWave's free assessment identifies which of these signals are present. On-site, efficiency is measured by comparing the actual flow temperature against the expected value for the current outdoor temperature — a reading GreenWave engineers take before starting any work.

Weather compensation (also called outdoor temperature reset) is a setting that automatically adjusts the flow temperature of the heat pump based on the outdoor temperature. On a mild day the heat pump sends cooler water to the radiators or underfloor heating; on a cold day it sends warmer water. This matters because heat pumps produce heat far more cheaply at lower temperatures — the relationship is called the Coefficient of Performance (COP). A heat pump running at 35°C flow temperature might achieve a COP of 4.0 (4 units of heat per unit of electricity), while the same heat pump running at 60°C flow might achieve only 2.0. Many heat pumps installed in Ireland are running without weather compensation active, which can double the running cost.

A heating curve (also called a weather compensation curve or WD curve) is a graph with outdoor temperature on one axis and target flow temperature on the other. It defines exactly what flow temperature the heat pump should produce at each outdoor condition. The steepness of this curve — called the gradient or slope — determines how aggressively the flow temperature changes with the weather. A flat gradient (0.3–0.6) is typical for well-insulated homes with underfloor heating. A steeper gradient (0.8–1.5) is typical for older properties with smaller radiators. Setting the heating curve correctly requires on-site testing over several days to verify that rooms reach temperature at different outdoor conditions without overheating when the weather is mild. GreenWave engineers calibrate the heating curve during every optimisation visit.

There is no single correct flow temperature — it depends on the outdoor temperature, the size of your radiators or underfloor heating, and how well insulated your property is. As a general guide for an average Irish property: at 0°C outdoor temperature, the flow temperature should typically be 40–50°C for a radiator system or 30–40°C for underfloor heating. At 10°C outdoor temperature, 30–40°C for radiators or 25–35°C for underfloor heating. Many heat pumps installed in Ireland are running at fixed flow temperatures of 55–65°C, which were carried over from the previous boiler installation. These temperatures are far too high for a heat pump and significantly increase running costs.

Delta-T (ΔT) is the temperature difference between the water leaving the heat pump (flow) and the water returning to it (return). For most heat pump systems the ideal delta-T during heating is 5–7°C. A delta-T below 3°C typically means the circulating pump is running too fast, a bypass valve is partially open, or the flow temperature set point is too low relative to the outdoor conditions. A delta-T above 10°C typically means restricted flow — often a blocked strainer, a closed zone valve, or a circulation pump that is running too slowly or has failed. GreenWave engineers measure delta-T as the first reading during any engineer visit.

SCOP (Seasonal Coefficient of Performance) is the ratio of heating energy produced to electrical energy consumed over a full heating season. A SCOP of 3.5 means the heat pump produces 3.5 units of heat for every 1 unit of electricity. For the Irish climate, a well-configured modern air source heat pump should achieve a SCOP of 3.0–4.5 for space heating. A poorly configured heat pump — particularly one running at unnecessarily high flow temperatures — may achieve a SCOP as low as 1.5–2.0, which is barely more efficient than direct electric heating and significantly more expensive than expected. Most heat pump manufacturers publish SCOP figures based on standard test conditions; actual in-use SCOP depends heavily on installation quality and configuration.

Short cycling (the heat pump turning on for a short period, switching off, then turning on again quickly) is usually caused by the heat pump overshooting its flow temperature target. This happens when the flow temperature set point is reached quickly before the heat has time to distribute through the circuit. The fix is usually one or more of: reducing the flow temperature set point, increasing the minimum run-time setting in the controller, adding a buffer tank if one is not fitted, or checking that all zone valves are opening correctly. Short cycling causes compressor wear and significantly reduces efficiency. GreenWave's optimisation visit addresses short cycling directly.

Heat pumps should be serviced annually. Unlike gas boilers there are no combustion components, but annual servicing is still essential for: verifying system pressure and topping up if needed, checking and cleaning the strainer/filter, inspecting and cleaning the outdoor unit coil, verifying flow temperatures and heating curve settings, checking DHW scheduling and temperatures, and confirming that all controller settings are still correctly configured. Most manufacturers require annual servicing as a condition of the warranty. A heat pump that is not serviced will gradually drift from its optimal configuration and cost more to run over time.

GreenWave's fixed prices including VAT are: Annual Service €239 (full health check, settings verification, written report), Fault Diagnostic from €179 (root cause investigation of fault codes or heating failures), Performance Optimisation €329 (weather compensation setup, curve calibration, DHW scheduling, before and after report), Full System Diagnostic €449 (comprehensive investigation for complex cases with multiple issues). There are no call-out fees, no hidden extras, and every service includes a written report. The free online assessment identifies which service is appropriate before you spend anything.

The GreenWave annual service includes: pre-visit baseline readings (flow temperature, return temperature, system pressure, outdoor temperature), outdoor unit inspection and coil cleaning, strainer and filter check and clean, system pressure verification and top-up, flow temperature verification against the expected heating curve for current outdoor conditions, DHW temperature and schedule check, controller settings audit, weather compensation verification, fault history review, and a written performance report showing before and after readings. Where settings are found to be suboptimal they are corrected during the visit.

A gas-registered engineer can carry out basic maintenance tasks — checking pressure, cleaning the outdoor unit, inspecting pipework. However, optimising a heat pump for efficiency requires knowledge that is specific to heat pumps and not part of gas boiler training. Weather compensation, heating curves, delta-T, minimum run-time, hot water scheduling, and the interaction between these settings are heat pump concepts. An engineer applying boiler logic to a heat pump — for example, setting a fixed high flow temperature to guarantee rooms stay warm — will leave the system running but at a fraction of its possible efficiency. GreenWave engineers are trained specifically in heat pump performance.

An annual service typically takes 90–120 minutes. A fault diagnostic visit is usually 60–90 minutes depending on the complexity of the fault. A performance optimisation visit is 120–150 minutes as it involves measuring, adjusting, waiting for the system to stabilise, and re-measuring to confirm improvement. A full system diagnostic can take up to 3 hours. GreenWave provides an estimated duration based on your assessment before any visit is booked.

Note the exact code displayed and your heat pump brand, then look it up using GreenWave's fault code guide. Common codes by brand: Samsung — E4 (high pressure trip, usually blocked outdoor coil or low charge), E9 (communication error between indoor and outdoor units), P1 (power supply voltage fault). Daikin — U4 (communication failure), E3 (high pressure), EA (refrigerant system fault). Mitsubishi — E6 (communication error), P8 (outdoor fin temperature). LG — CH10 (low pressure), CH12 (high pressure). Do not continue using the system if the fault code is disabling heating or indicates a refrigerant issue. Complete GreenWave's free assessment and select "fault code showing" to get a recommended next step.

The most common causes in order of frequency: 1. Flow temperature set point is too low for the current outdoor conditions and the size of the radiators (most common). 2. Weather compensation is active with a gradient that is too flat, meaning the flow temperature doesn't rise enough as the outdoor temperature drops. 3. A fault code has put the system in a protection or reduced-capacity mode. 4. System pressure is too low, causing the low-pressure switch to activate. 5. One or more zone valves are stuck closed, preventing circulation in part of the house. 6. The circulating pump has failed or is running at the wrong speed. GreenWave's fault diagnostic visit identifies the exact cause with a written report.

Common causes: the DHW target temperature is set too low (should usually be 50–55°C), the DHW schedule is not running at the right times, the immersion heater is not activating for the weekly legionella cycle (which should raise the cylinder to 60°C), the heat pump is prioritising space heating over DHW and not completing the DHW cycle, or the cylinder is undersized for the number of occupants. GreenWave's annual service includes a full DHW audit covering target temperature, schedule, legionella cycle, and cylinder recovery time.

Several things can change between heating seasons. System pressure can drop gradually if there is a slow leak. Controller settings can be accidentally changed during summer. The outdoor unit coil can become fouled with dust, pollen or debris from vegetation, reducing heat exchange efficiency. Settings that worked adequately at mild outdoor temperatures can be insufficient at lower temperatures that only occur in colder winters. The heat pump may also have developed a refrigerant charge issue that is only apparent at maximum load. A GreenWave annual service at the start of the heating season catches all of these before they become a problem.

System pressure refers to the water pressure in the sealed heating circuit. It should read 1.0–1.8 bar when the system is cold. Below 1.0 bar the low pressure switch may activate, preventing the circulating pump from running properly. Low pressure is caused by water loss from the circuit — either through a slow leak at a joint or radiator valve, or because the expansion vessel pre-charge has dropped and the pressure relief valve has discharged water. To top up pressure, find the filling loop — a braided flexible hose with a quarter-turn valve, usually under the indoor unit — and open it slowly until the gauge reads 1.3 bar, then close it fully. If pressure drops again within days, there is a leak that requires a GreenWave engineer visit to locate and fix.

Yes. A heat pump can work effectively with radiators, but there are important differences from a boiler installation. A heat pump produces heat most efficiently at lower flow temperatures (35–50°C), whereas most radiator systems were designed for boiler flow temperatures of 70–80°C. This means existing radiators may need to be upsized — or additional radiators added — to emit enough heat at lower temperatures. In practice, many Irish heat pump installations with existing radiators work well, particularly in well-insulated properties. Underfloor heating is the most efficient emitter for heat pumps because it works at even lower flow temperatures (25–35°C).

A buffer tank is a small unpressurised water tank (typically 80–200 litres) fitted between the heat pump and the heating circuit. It gives the heat pump a larger volume of water to heat, which prevents short cycling when the heating demand is low. Whether you need a buffer tank depends on your system: if you have a large emitter surface (big underfloor heating areas or many large radiators) a buffer tank is usually not needed. If you have a small heating circuit, multiple zones that can all close simultaneously, or a heat pump that is slightly oversized for your property, a buffer tank will improve efficiency significantly. GreenWave can advise during a service visit.

The hot water cylinder (DHW) target temperature should usually be set to 50°C for daily use. This is hot enough for comfortable use while being achievable efficiently by the heat pump. Once per week the immersion heater should be activated to raise the cylinder temperature to 60°C for a legionella protection cycle (this is a health and safety requirement). Many heat pump controllers include a built-in schedule for this. Setting the DHW temperature above 55°C as a daily target is unnecessary and significantly increases electricity use, as heat pumps are much less efficient at higher temperatures.

An air source heat pump (ASHP) extracts heat from the outdoor air and is the most common type installed in Irish homes. It has an outdoor unit (similar in appearance to an air conditioning unit) and works down to around -20°C outdoor temperature. A ground source heat pump (GSHP) extracts heat from the ground through pipes buried in the garden (horizontal loops) or deep boreholes (vertical). Ground source heat pumps achieve higher efficiency than air source because ground temperature is more stable than air temperature, but they cost significantly more to install. GreenWave currently focuses on air source heat pump servicing and optimisation.

GreenWave Connect is an optional monthly monitoring subscription at €10 per month including VAT. Once connected to your heat pump system, it provides: weekly performance summaries showing how your system is running, efficiency tracking over time, early detection of performance issues before they become faults, and priority scheduling for GreenWave service visits. Connect is available as an add-on after completing the free assessment.

No obligation whatsoever. The assessment is free, your results are immediate, and there is no follow-up sales call. You can complete the assessment, view your health indicators, and close the page — that's it. If you decide you'd like a GreenWave engineer visit, you can request one from your results page at any time. No payment is collected until a visit is confirmed and agreed.