NIBE S735.
The facts, straight from the data sheet.
Heating, hot water and ventilation from one compact unit. Every figure on this page links to the official document it came from, so you never have to take anyone's word for it, including ours.
Over 26 years of NIBE in Ireland, since 2000 · All 32 counties · Download the technical brochure
The numbers that matter, and where they come from
Figures are from the ErP product data sheets (EN 14825, average climate) unless stated. Tap any source to open the document.
ηs at 35°C. The S735-7 is 177%. Energy class A+++ at 35°C.
Source: ErP data sheetUsed by NIBE since 1998, in over 150,000 heat pumps.
Source: Technical brochureNo anode needed. XL tap profile, up to 264 L of hot water at 40°C.
Source: NIBE S735 product pageLWA indoors. The S735-7 is 44 dB(A) and Quiet Mark certified.
Source: ErP data sheet
It recovers the heat your home already paid for
- 1Warm air is drawn outA single fan extracts used air at around 22°C from the bathrooms, en-suites and kitchen.
- 2Fresh air comes inThe slight negative pressure draws fresh air through discreet wall vents in the other rooms.
- 3The heat is recoveredThe inverter driven compressor takes the energy out of that air before it leaves the building, at around minus 15°C.
- 4Your home gets it backThat energy heats your radiators or underfloor heating and the hot water in the built in cylinder.
Works with radiators or underfloor heating, piped as normal. Weather compensation sets the flow temperature from the outdoor sensor and your heat curve, and myUplink lets you or your installer check the system from a phone.
Watch how it works, 1:12S735-4 and S735-7, side by side
Last checked against the published documents: September 2026. If a document is updated, the document wins.
| Specification | NIBE S735-4 | NIBE S735-7 | Source |
|---|---|---|---|
| Rated heat output, Prated (35°C) | 3.5 kW | 5.6 kW | ErP data sheets |
| Seasonal space heating efficiency, ηs (35°C) | 187% | 177% | ErP data sheets |
| Energy class, space heating 35°C / 55°C | A+++ / A++ | A+++ / A++ | NIBE product page |
| Water heating efficiency, ηwh | 117% | 117% | ErP data sheets |
| Hot water tap profile / class | XL / A | XL / A | ErP data sheets |
| Sound power level, LWA (indoor) | 42 dB(A) | 44 dB(A) | ErP data sheets |
| Annual electricity consumption (average climate) | 1,430 kWh | 1,432 kWh | ErP data sheets |
| Minimum ventilation flow for optimum performance | 60 m³/h (17 l/s) | 90 m³/h (25 l/s) | Installer manual |
| Heating water operating limit | 65°C | 65°C | ErP data sheets |
| Capacity control | Variable, inverter | Variable, inverter | ErP data sheets |
| Refrigerant | R290, GWP 3 | R290, GWP 3 | NIBE product page |
| Built in hot water cylinder | 180 L stainless steel | 180 L stainless steel | Technical brochure |
| Hot water available at 40°C | Up to 264 L | Up to 264 L | NIBE product page |
| Supplementary immersion | 3.5 kW, single phase | 3.5 kW, single phase | Technical brochure |
| Dimensions, H x W x D | 2025 x 600 x 620 mm | 2025 x 600 x 620 mm | NIBE product page |
| Net weight | 200 kg | 200 kg | NIBE product page |
| Connectivity | myUplink, USB port | myUplink, USB port | Technical brochure |
| Test standards | EN 14825, EN 16147, EN 12102-1 | EN 14825, EN 16147, EN 12102-1 | ErP data sheets |
S735-7 ErP figures are from the S735-7 E data sheet. Energy classes are from NIBE's product page. For the S735C with active cooling, see below.
The same S735, with active cooling built in
For homes that overheat in summer, the S735C adds a cooling function to heating, hot water and ventilation. Available as S735C-4 and S735C-7, each in CU, E and R versions.
Source: NIBE S735C product pageHeard something about the S735? Here is what the documents say.
Things people sometimes get told about exhaust air heat pumps, answered with the published figures.
See the S735 for yourself
Short videos from NIBE and our own service team, for homeowners, site maintenance teams and installers.
Every S735 document in one place
12 pages covering how it works, verified technical data for the S735-4, S735-7 and S735C, the SAM S42 supply air module for Passive House, heating system layouts, and links to every data sheet, DEAP example and BIM file.
Download brochure, PDF 7.5 MBProduct data to EN 14825, 35°C, average climate.
NIBE S735-4 data sheetPDF NIBE S735-7 data sheetPDF Circulation pump curveJPG
55°C energy labels for each model.
NIBE S735-4 energy labelPDF NIBE S735-7 energy labelPDFWorked data entry examples for BER assessors.
NIBE S735-4 DEAP data entryPDF NIBE S735-7 DEAP data entryPDFFor installers, specifiers and homeowners.
Installer manualPDF Installer manual, latest from NIBEPDF User manualPDF Unipipe S735 technical brochurePDFThe cooling variant, from NIBE’s library.
S735C installer manualPDF S735C user manualPDF S735C-4 energy labelPDF S735C-7 energy labelPDF S735C consumer information leafletPDFOfficial documents from NIBE’s own library.
Consumer information leafletPDF Product leafletPDF Exhaust air cataloguePDFNIBE's first heat pump was an exhaust air heat pump. That was 1981.
Unipipe's first NIBE exhaust air installation was in 2000, and we have supported every generation since. We carry spare parts in Ireland for every machine supplied since 2000, run our own team of NIBE service engineers, and take weekly deliveries from Markaryd, Sweden.
S735 schemes include Tinakilly Park, Co. Wicklow and Dalkey Forge, Dublin. See our projects
Specifying an S735?
Talk to the people who have supplied and supported NIBE in Ireland for over 26 years, since 2000.
