Heat Pump Noise Calculator at the Neighbour
Estimate heat pump noise at a neighbour's window from sound power, placement, distance and barriers. Includes dated German night and England MCS presets.
This heat pump noise calculator estimates the A-weighted level at a neighbour's window before you commit to an outdoor-unit location. It is for engineers, installers, students and householders comparing equipment, separation distances and screening measures. Start with a manufacturer's sound-power value: a sound-pressure value measured at a stated distance is a different quantity and cannot be entered directly.
Choose the assessment rules first. The German preset uses TA Lärm night limits for pure residential, general residential and mixed or urban areas. It subtracts the LAI guide's 6 dB planning allowance from the selected limit. This allowance reserves room for other installations; it is separate from a manufacturer's uncertainty allowance. The calculation assumes continuous operation during the loudest night hour. Unknown tonality defaults to a 3 dB rating addition. Confirm the receiving property's area designation rather than inferring it from the appearance of the street.
The England preset implements the acoustic calculation in MCS 020 a), Issue 1.1 of 14 April 2025. England incorporated that issue into permitted-development rules on 29 May 2025. It uses the manufacturer's declared sound power without a low-noise-mode reduction, rounds the slant distance to 0.1 m and compares the final level, rounded to 0.1 dB, with 37.0 dB(A). Other UK jurisdictions and other planning conditions require separate checks. An MCS 020 calculation here is a sound screening result, not planning approval or an installer certificate.
Enter the horizontal distance to the neighbour's window plane and the two heights. The receiver is placed 0.5 m in front of the German window or 1 m in front of the English window. Reflecting surfaces alter directivity. For MCS, select one, two or three qualifying surfaces; an elevated unit against a single wall can have Q = 2 without counting distant ground. A second unit can have its own sound power, placement and shielding, with a lateral offset along the same wall. Both units operate simultaneously. Their contributions add as acoustic energies, so equal contributions increase the total by about 3 dB.
Only claim barrier credit when the construction and sight line justify it. Vegetation and fences with gaps provide no MCS credit. For Germany or a custom target, leave insertion loss at zero unless supported by acoustic evidence. The plan view shows unshielded rings from unit 1 at the window height; the result cards include all enabled units and selected corrections. The distance chart holds those corrections fixed while exploring separation.
A separate German field group screens the BEG source-emission criterion effective from 1 January 2026 using declared ErP sound power. It does not replace the neighbour assessment or establish subsidy eligibility. This Wärmepumpe Schallrechner supports early decisions; it does not assess low-frequency disturbance, vibration, short noise peaks or complex reflections. Installation work belongs to a qualified person. Check against the standard and regulations in force, and obtain an expert noise report where site conditions or a small margin require one.
How it is calculated
Rules snapshot: 27 October 2026. The England acoustic calculation follows MCS 020 a), Issue 1.1, 14 April 2025, steps 3–8 (attached source s1, pp.12–15). England adopted that issue on 29 May 2025; applicability elsewhere in the UK must be checked locally.
For each unit, the point-source model is
The path includes the source-to-window height difference and unit 2's lateral offset. The reflecting-surface count sets Q: one gives 2, two give 4, three give 8. Under MCS, count only surfaces within 1 m that extend at least 1 m beyond the unit in two directions; the ground counts only when it qualifies. Thus an elevated unit against one qualifying wall has Q = 2, against two walls Q = 4, and between three walls Q = 8 (s1, pp.12–13). For Germany/custom, the conservative model includes the ground and adds the nearby walls selected by the count. Do not add another ground or receiving-façade reflection correction. MCS distances and the final summed level are rounded to 0.1 m and 0.1 dB respectively. MCS barrier construction and visibility determine the insertion loss; full visibility always gives zero.
Independent sources combine through
For German screening, add each unit's tonal allowance before combining its rating contribution. Continuous operation in the loudest night hour is assumed; no duty-cycle reduction is taken.
German method: conservative short-range spherical propagation, informed by the LAI guide of 28 August 2023 (s2, pp.9–11), with the TA Lärm night limit minus 6 dB as the planning target. This is an engineering approximation to LAI guidance, not its tabulated distance procedure: the latter includes height-dependent ground reflection, ground attenuation and atmospheric absorption. This calculator uses fixed Q and omits propagation attenuation beyond spreading; it does not reproduce an ISO 9613-2 assessment. German wall proximity follows the LAI guidance, whereas England uses the MCS proximity definition given beside the input.
Separate source criterion: for German BEG applications from 1 January 2026, compare the declared ErP outdoor sound power per unit with the applicable EU 813/2013 outdoor ceiling minus 10 dB. Rated thermal output determines the band. This source test uses its own declared sound power, because a guaranteed night-mode value used for neighbour screening may differ. The displayed source result covers that acoustic criterion only.
Assumptions
- One receiver per run; repeat for every potentially affected habitable-room opening, including upper floors and other directions. Geometry places unit 1 opposite the window and unit 2 laterally along the same plane, at the same height.
- German assessment point: 0.5 m outside the open window; England: 1 m external to the opening's centre. The receiving façade is excluded from the predicted incident level.
- The sources are incoherent point sources, operating simultaneously and continuously. Q models ideal nearby reflecting planes; it does not describe a measured fan directivity pattern. In MCS mode, height does not automatically count the ground: assess proximity to the actual unit casing, including any roof or platform.
- German unknown tonality defaults to 3 dB following LAI. Impulsiveness, start/stop peaks, defrost events and structural transmission need separate examination.
- German and custom barrier insertion losses require evidence for the actual source–receiver path. No screening credit is assumed by default. An MCS barrier is gap-free, extends at least 1 m beyond each side of the unit and meets the selected thickness class. The sight-line test starts at the unit's top edge; partial visibility means the point becomes visible within a 0.25 m move.
- The drawing is an original idealized plan: unit 1 only, rings of incident sound pressure at window height, without barrier attenuation or tonal additions. Building and unit symbols are schematic. In MCS mode, nearby wall orientations are omitted because the input specifies only a surface count. Rings at slant distances below 1 m are omitted because they are outside the point-source model. Unit 2 intermediates apply only when the second unit is enabled.
- The distance chart is continuous before MCS rounding and holds directivity, barrier credit, heights and the lateral offset fixed. Reassess those choices if moving the installation changes them.
Where it applies
Use for early outdoor siting comparisons with straight-line source–receiver distances of about 1–50 m. The model is unsuitable for lightwells, reverberant courtyards, more than three nearby reflecting surfaces, indoor noise, vibration transmission or low-frequency nuisance. A-weighted compliance alone cannot rule out disturbance.
German presets cover ordinary residential and mixed/urban night cases (22:00–06:00, loudest full hour). They do not assess day averaging, sensitive periods, short-term maxima, unusual zoning or the total contribution of unrelated existing plant. The 6 dB allowance is a planning criterion and does not itself guarantee legal acceptability. The LAI distance-table values will differ from this conservative spreading approximation.
The England preset is the acoustic part of MCS 020 a) Issue 1.1, not a complete permitted-development assessment. Two units are allowed by the count restriction only for a detached house; all other planning limitations and all assessment positions still require checking. Do not transfer England's legal preset to Scotland, Wales or Northern Ireland without checking their rules.
BEG 2026 screening applies to the stated air-to-water outdoor-unit source criterion in the 0.5–70 kW rated-output range. Other funding requirements and the applicable product listing remain separate. Check against the standard and regulations in force. This tool is not an expert noise report. Installation work belongs to a qualified person; involve an acoustician and the relevant authority when evidence or margin is insufficient.
References
- [MCS 020 a), Issue 1.1, 14 April 2025](https://mcscertified.com/wp-content/uploads/2025/04/MCS-020-a-Issue-1.1-Final.pdf), steps 3–8, pp.12–15; independent worked examples pp.18–20. Attached as s1 from an open [local-authority copy](https://planningregister.cherwell.gov.uk/Document/Download?fileName=MCS-020-a-Issue-1.1-Final.pdf&imageId=25&isPlan=False&module=PLA&planId=2381240&recordNumber=163825).
- [LAI stationary equipment noise guide, long version, 28 August 2023](https://lai-immissionsschutz.de/media/leitfaden-laerm-bei-stationaeren-geraeten-langfassung_1698052163.pdf), pp.5 and 9–11: outdoor product ceilings, planning allowance, reflecting surfaces, tonality and limits of simplified propagation. Attached as s2.
- [TA Lärm, 26 August 1998, amended 2017](https://www.verwaltungsvorschriften-im-internet.de/bsvwvbund_26081998_IG19980826.htm), §§6.1, 6.4 and A.1.3: night limits, assessment times and receiver position. Checked 27 October 2026.
- [England GPDO Amendment Order 2025, SI 2025/560](https://www.legislation.gov.uk/uksi/2025/560/contents/made), articles 1, 5 and 6: commencement 29 May 2025, unit-count restrictions and reference to MCS 020 a) Issue 1.1.
- [BAFA: BEG heat-pump efficiency and eligibility evidence](https://www.bafa.de/SharedDocs/Downloads/DE/Energie/beg_waermepumpen_pruef_effizienznachweis.pdf?__blob=publicationFile&v=5), section 6: outdoor emissions at least 10 dB below EU 813/2013 ceilings from 1 January 2026.
- [Commission Regulation (EU) No 813/2013](https://eur-lex.europa.eu/eli/reg/2013/813/oj), Annex II §3: rated-output-dependent outdoor sound-power ceilings. Thresholds also reported by LAI 2023 p.5.
Inputs
| Input | Symbol | Unit | Default |
|---|---|---|---|
| Assessment preset Germany: TA Lärm (1998, amended 2017) with the LAI guide of 28 August 2023. England: MCS 020 a), Issue 1.1, 14 April 2025, with a 37.0 dB(A) limit. Rules checked 27 October 2026. England's preset is not a UK-wide planning permission test. Repeat for every affected window. | rules | Germany — night | |
| German area at the receiving window TA Lärm night limits (22:00–06:00): pure residential WR 35 dB(A); general residential WA 40 dB(A); mixed, village, core and urban areas 45 dB(A). With the 6 dB LAI allowance, the corresponding planning targets are 29, 34 and 39 dB(A). Confirm the receiving property's designation with the authority. | zone | WA — general residential | |
| Custom assessment target | L_custom | dB | 40 |
| Custom assessment offset in front of window | setback_custom | m | 0.5 |
| Simultaneously operating outdoor units | n_units | 1 | |
| Property receiving the heat pump installation In England the 2025 permitted-development count ceiling is two units for a detached house and one otherwise. Other planning conditions still apply. | dwelling | Detached house | |
| Horizontal distance to neighbour's window plane Unit 1 is opposite the window. The assessment point is 0.5 m before the window in Germany, 1 m in England. Measure to the window, not the boundary. | D_window | m | 10.5 |
| Acoustic centre height of both units Height of the acoustic centre, used for slant distance. For England, decide separately which surfaces qualify within 1 m of the actual unit. An elevated unit may have a qualifying wall while the distant ground does not qualify. Germany/custom retain the conservative ground-plane assumption. | h_source | m | 0.8 |
| Window centre height The model uses the straight-line slant distance, including this height difference. | h_window | m | 2 |
| Unit 2 lateral separation along the wall Both units share the same distance to the window plane and source height. Zero represents an equivalent group at the same distance. | y_unit2 | m | 3 |
| Unit 1 A-weighted sound power LWA Sound POWER, not pressure. England: use the manufacturer's standard declared value; low-noise mode is excluded. Germany: use the highest possible night value unless a lower mode is guaranteed. | L_w1 | dB | 55 |
| Unit 1 reflecting-surface count England (MCS): count surfaces within 1 m that extend at least 1 m beyond the unit in two directions. Count the ground only if it qualifies. One surface can be ground alone or one wall for an elevated unit; two can be ground + wall or two elevated walls; three can be ground + two walls or three elevated walls. Germany/custom: include the ground, then nearby walls within 3 m (two walls also if at most 5 m apart). Other MCS surface counts require specialist assessment. | placement1 | 2 surfaces — Q = 4 | |
| Unit 1 tonal character allowance LAI 2023 recommends 3 dB if tonality is unknown. This is a rating addition, not extra physical sound pressure. | tone1 | Unknown or audible tone — 3 dB | |
| Unit 1 MCS barrier construction A qualifying barrier must extend ≥1 m beyond both sides of the unit. Judge the line of sight to this assessment point from the unit's top edge. | barrier1 | None / vegetation / gaps / slats | |
| Unit 1 view from its top edge | sight1 | Assessment point directly visible | |
| Unit 1 verified barrier insertion loss Leave at zero without acoustic evidence for this path and window height. This tool does not design barriers. Do not assign building-screening credit to a garden fence. | A_verified1 | dB | 0 |
| Unit 1 rated thermal output (ErP) For the source-emission criterion only; does not affect propagation. Use the applicable ErP rated thermal output, not electrical input. | P_heat1 | kW | 8 |
| Unit 1 declared ErP outdoor sound power Enter the declared emission for subsidy evidence separately from a guaranteed night-mode value. The 2026 BEG criterion is at least 10 dB below the EU 813/2013 outdoor limit; this is not full subsidy eligibility. | L_erp1 | dB | 55 |
| Unit 2 A-weighted sound power LWA Sound POWER, not pressure. England: use the manufacturer's standard declared value; low-noise mode is excluded. Germany: use the highest possible night value unless a lower mode is guaranteed. | L_w2 | dB | 55 |
| Unit 2 reflecting-surface count England (MCS): count surfaces within 1 m that extend at least 1 m beyond the unit in two directions. Count the ground only if it qualifies. One surface can be ground alone or one wall for an elevated unit; two can be ground + wall or two elevated walls; three can be ground + two walls or three elevated walls. Germany/custom: include the ground, then nearby walls within 3 m (two walls also if at most 5 m apart). Other MCS surface counts require specialist assessment. | placement2 | 2 surfaces — Q = 4 | |
| Unit 2 tonal character allowance LAI 2023 recommends 3 dB if tonality is unknown. This is a rating addition, not extra physical sound pressure. | tone2 | Unknown or audible tone — 3 dB | |
| Unit 2 MCS barrier construction A qualifying barrier must extend ≥1 m beyond both sides of the unit. Judge the line of sight to this assessment point from the unit's top edge. | barrier2 | None / vegetation / gaps / slats | |
| Unit 2 view from its top edge | sight2 | Assessment point directly visible | |
| Unit 2 verified barrier insertion loss Leave at zero without acoustic evidence for this path and window height. This tool does not design barriers. Do not assign building-screening credit to a garden fence. | A_verified2 | dB | 0 |
| Unit 2 rated thermal output (ErP) For the source-emission criterion only; does not affect propagation. Use the applicable ErP rated thermal output, not electrical input. | P_heat2 | kW | 8 |
| Unit 2 declared ErP outdoor sound power Enter the declared emission for subsidy evidence separately from a guaranteed night-mode value. The 2026 BEG criterion is at least 10 dB below the EU 813/2013 outdoor limit; this is not full subsidy eligibility. | L_erp2 | dB | 55 |
Results
With the default inputs above, the calc gives:
| Result | Value |
|---|---|
| This assessment point | Within screening target |
| Assessment level — A-weighted | 33 dB |
| Screening target — A-weighted | 34 dB |
| Margin below target (+ is below) | 1 dB |
| Combined sound pressure — A-weighted | 30 dB |
| BEG 2026 source criterion only | Source criterion met |
Checked against sources
Each case below was calculated by this calc and agrees with the value from its source (within the tolerance where one is shown).
MCS Appendix A: first-floor window, partial shielding
Source: MCS 020 a) Issue 1.1 (14 April 2025), Appendix A p.18: LWA 60, Q4, r=8.0 m, brick wall and partial line of sight; published rounded result 32.0 dB(A). Equal heights here reproduce its given slant distance.
Inputs: Assessment preset = England — MCS; Unit 1 A-weighted sound power LWA = 60 dB; Horizontal distance to neighbour's window plane = 9 m; Acoustic centre height of both units = 1.5 m; Window centre height = 1.5 m; Unit 1 MCS barrier construction = Masonry or gap-free fence ≥18 mm thick; Unit 1 view from its top edge = Visible after moving up to 0.25 m; the others as above.
| Result | Source | This calc |
|---|---|---|
| Unit 1 calculation distance (MCS: nearest 0.1 m) | 8 m | 8 m |
| Unit 1 barrier attenuation | 5 dB | 5 dB |
| Assessment level — A-weighted | 32 dB | 32 dB |
MCS Appendix A: ground-floor window, fully shielded
Source: MCS 020 a) Issue 1.1, Appendix A p.19: LWA 60, Q4, r=5.0 m and no line of sight over a brick wall; rounded result 31.0 dB(A).
Inputs: Assessment preset = England — MCS; Unit 1 A-weighted sound power LWA = 60 dB; Horizontal distance to neighbour's window plane = 6 m; Acoustic centre height of both units = 1.5 m; Window centre height = 1.5 m; Unit 1 MCS barrier construction = Masonry or gap-free fence ≥18 mm thick; Unit 1 view from its top edge = Fully obscured, including the 0.25 m margin; the others as above.
| Result | Source | This calc |
|---|---|---|
| Unit 1 barrier attenuation | 10 dB | 10 dB |
| Assessment level — A-weighted | 31 dB | 31 dB |
MCS Appendix A: visible source through slatted fence
Source: MCS 020 a) Issue 1.1, Appendix A p.20: LWA 60, Q4, r=15.0 m and a slatted fence; rounded result 31.5 dB(A).
Inputs: Assessment preset = England — MCS; Unit 1 A-weighted sound power LWA = 60 dB; Horizontal distance to neighbour's window plane = 16 m; Acoustic centre height of both units = 1.5 m; Window centre height = 1.5 m; the others as above.
| Result | Source | This calc |
|---|---|---|
| Unit 1 barrier attenuation | 0 ± 0.001 dB | 0 dB |
| Assessment level — A-weighted | 31.5 dB | 31.5 dB |
Published EU outdoor ceilings and 2026 BEG reduction: 6 and 12 kW
Source: LAI 2023 p.5 reports the independent EU 813/2013 outdoor ceilings of 65 dB at ≤6 kW and 70 dB at >6–12 kW. BAFA BEG evidence section 6 requires 10 dB below these from 1 January 2026, giving 55 and 60 dB. https://www.bafa.de/SharedDocs/Downloads/DE/Energie/beg_waermepumpen_pruef_effizienznachweis.pdf?__blob=publicationFile&v=5
Inputs: Simultaneously operating outdoor units = 2; Unit 1 rated thermal output (ErP) = 6 kW; Unit 2 rated thermal output (ErP) = 12 kW; Unit 2 declared ErP outdoor sound power = 60 dB; the others as above.
| Result | Source | This calc |
|---|---|---|
| Unit 1 BEG 2026 source threshold | 55 dB | 55 dB |
| Unit 2 BEG 2026 source threshold | 60 dB | 60 dB |
| Lowest BEG source margin among enabled units | 0 ± 0.001 dB | 0 dB |
Published EU outdoor ceilings and 2026 BEG reduction: 30 and 70 kW
Source: LAI 2023 p.5 reports the independent EU 813/2013 outdoor ceilings of 78 dB at >12–30 kW and 88 dB at >30–70 kW. The separately published BAFA BEG 2026 reduction of 10 dB gives 68 and 78 dB; boundary output belongs to the lower band.
Inputs: Simultaneously operating outdoor units = 2; Unit 1 rated thermal output (ErP) = 30 kW; Unit 2 rated thermal output (ErP) = 70 kW; Unit 1 declared ErP outdoor sound power = 68 dB; Unit 2 declared ErP outdoor sound power = 78 dB; the others as above.
| Result | Source | This calc |
|---|---|---|
| Unit 1 BEG 2026 source threshold | 68 dB | 68 dB |
| Unit 2 BEG 2026 source threshold | 78 dB | 78 dB |
| Lowest BEG source margin among enabled units | 0 ± 0.001 dB | 0 dB |
Independent-review regression: elevated unit against one wall
Source: User-supplied independent-review case: England, acoustic and window heights 5 m, LWA 62 dB, default window distance 10.5 m and no barrier. The review gives 34.5 dB(A) for one qualifying wall (ground outside the 1 m criterion). This is a regression supplied by the reviewer, not a published MCS worked example. MCS 020 a) Issue 1.1 pp.12–13 establishes the qualifying-surface rule and Q = 2 for an elevated unit against one wall.
Inputs: Assessment preset = England — MCS; Unit 1 A-weighted sound power LWA = 62 dB; Unit 1 reflecting-surface count = 1 surface — Q = 2; Acoustic centre height of both units = 5 m; Window centre height = 5 m; the others as above.
| Result | Source | This calc |
|---|---|---|
| Unit 1 directivity factor | 2 | 2 |
| Assessment level — A-weighted | 34.5 dB | 34.5 dB |
| Margin below target (+ is below) | 2.5 dB | 2.5 dB |
MCS elevated examples: two and three qualifying walls
Source: MCS 020 a) Issue 1.1 p.13 explicitly gives Q4 for an elevated unit against two walls and Q8 for an elevated unit between three walls. The two sources verify both placement inputs without assuming that the ground qualifies.
Inputs: Assessment preset = England — MCS; Simultaneously operating outdoor units = 2; Unit 2 reflecting-surface count = 3 surfaces — Q = 8; Acoustic centre height of both units = 5 m; Window centre height = 5 m; the others as above.
| Result | Source | This calc |
|---|---|---|
| Unit 1 directivity factor | 4 | 4 |
| Unit 2 directivity factor | 8 | 8 |
Responses