Water-to-Water Heat Pump Patents: Who Leads, Where the Gaps Are 2026
- No single filer dominates. the ranked leader holds 3,235 records and the top 10 combined cover just 5.3% of all 360,220 records in scope.
- Filing has plateaued, not grown. activity peaked in 2022 at 940 filings and the 2017–2026 trend sits flat to declining once the partial latest year is set aside.
- Core refrigeration classes are thinly claimed. F25B (refrigeration & heat pumps) covers only 0.2% of records and F24D (domestic heating) 0.2%, well behind adjacent water-treatment and materials classes.
Filing growth compares 2021 (886 records) with 2024 (580) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 360,220 records in scope (CR5), not by the ranked leaders only.
What this dataset covers
The search set spans 360,220 published records filed between 2015 and mid-2026, built around claim language for supply temperature thresholds, cascade and two-stage cycles, compressor discharge temperature and system integration in water-based heat transfer. It captures both dedicated heat-pump filings and a large volume of adjacent water-treatment, materials and analytical patents that share the same search terms, which is why the IPC composition below is broader than a pure heat-pump taxonomy would suggest.
Because publication lags filing by roughly 18 months, the 2025 and 2026 figures in any trend line understate real activity; treat the last one to two years as a floor, not a ceiling.
Filing trend and technology composition
Two views of the same 360,220-record set: how filing volume has moved year over year, and which IPC subclasses carry the claim density.
A plateau, not a growth curve
Filings rose from 862 in 2017 to a peak of 940 in 2022, then eased back toward 34 in the still-partial 2026 count. The midpoint year matching the peak indicates the field has stopped expanding rather than accelerating into a new build-out.
Water treatment and materials classes outweigh core refrigeration
C02F (water & wastewater treatment) leads at 0.7% of the 360,220 records, followed by B01D separation processes at 0.6% and G01N materials testing at 0.5%. The refrigeration-specific classes — F25B heat pumps and F24H/F24D heaters — each sit at 0.2-0.3%, meaning the mechanical heat-pump cycle itself is a comparatively narrow slice of a much larger search space dominated by adjacent water and materials science.
Shares are the percentage of the 360,220 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Water-to-Water Heat Pumps for District and Industrial Heat with Eureka
This page is one run against one query. Ask Eureka your own question about water-to-water heat pumps for district and industrial heat and every answer comes back with the patent numbers behind it.
Try EurekaRepresentative and most-cited filings
US6715916B2 — Gas turbine firing and combustion reference temperature correction for water content
A system is disclosed for adjusting a gas turbine firing temperature control algorithm and combustion reference temperature algorithms based on exhaust gas temperature, turbine pressure ratio and compressor discharge temperature for water content in the air entering the compressor differing from the design water content of ambient air. The water content in the ambient air is calculated by the control system from measured data from a dry bulb temperature sensor and a wet bulb temperature or humidity sensor.Filed by General Electric, granted 2004-04-06 — control-layer claims on compressor discharge temperature correction rather than the heat exchanger hardware itself.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5760100A | Extended wear ophthalmic lens | 1,983 |
| 2 | US5322063A | Hydrophilic polyurethane membranes for electrochemical glucose sensors | 1,624 |
| 3 | US6241928B1 | Method for production of shaped hydrogel of absorbent resin | 1,110 |
| 4 | US5849811A | Extended wear ophthalmic lens | 981 |
| 5 | US20160045841A1 | New and improved system for processing various chemicals and materials | 855 |
| 6 | US5965631A | Extended wear ophthalmic lens | 828 |
| 7 | US5789461A | Methods of forming an extended wear ophthalmic lens having a hydrophilic surface | 717 |
| 8 | US5776999A | Methods of using and screening extended wear opthalmic lenses | 700 |
| 9 | US5591344A | Hot water disinfection of dialysis machines, including the extracorporeal circuit thereof | 687 |
| 10 | WO2005095618A2 | Plants with reduced activity of the starch phosphorylating enzyme phosphoglucan, water dikinase | 638 |
Citation counts favour older filings simply by virtue of time in the corpus; read them as a signal of influence on later work, not as a ranking of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns stand out once volume, concentration and technology composition are read together.
No gatekeeper to clear
The top 10 assignees combined hold 18,973 records, only 5.3% of the full 360,220-record set, and the leader alone accounts for 3,235. That is a long tail, not a fortress: a new entrant is not fighting through one or two dominant portfolios to find open claim space.
Filing has already crested
Year-over-year counts rise from 862 in 2017 to a peak of 940 in 2022 before falling back. Several of the more active historical filers show 0% or -100% year-over-year change in the latest year, consistent with a field that has stopped adding fresh claim volume even before accounting for publication lag.
Core heat-pump classes are thin
C02F water treatment (0.7%) and B01D separation (0.6%) outweigh F25B refrigeration/heat pumps and F24D domestic heating, each at 0.2%. The mechanical cycle hardware that defines a water-to-water heat pump is a narrow claim layer sitting underneath a much larger volume of water-processing and materials-testing filings that share this search vocabulary.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to water-to-water heat pumps for district and industrial heat, with the prior art for and against each one.
Who is filing, and where the gate sits
The ranked assignee list runs 100 companies deep with no dominant blocker at the top, which changes how a freedom-to-operate review should be scoped.
Largest portfolio, still a minority share
The top-ranked assignee holds 3,235 records out of 360,220 in scope — a meaningful lead over rank ten's 1,215, but nowhere near control of the field. Reviewing this portfolio narrows a search considerably without closing it.
A gradual, not a cliff-edge, drop-off
Filings fall from 3,235 at the top to 1,807 by fifth place and 1,215 by tenth, a gradual taper rather than a sharp cliff. That shape points to a fragmented competitive set where several mid-sized portfolios are worth checking individually.
US and EPO carry the bulk of filings
The United States receives the largest single share of filings at 10,311, ahead of the EPO at 3,702 and WIPO/PCT at 1,871, with Canada, the UK and Australia each above 1,000. Clearance work should prioritise these offices before extending to smaller jurisdictions.
| Assignee | Recent year | YoY |
|---|---|---|
| Procter & Gamble | 1 | 0% |
| Hitachi, Ltd. | 0 | — |
| Saudi Arabian Oil Company (Saudi Aramco) | 0 | -100% |
| Mitsubishi Electric Corporation | 0 | -100% |
| General Electric Company | 0 | — |
| BASF SE | 0 | -100% |
| Nippon Shokubai Co., Ltd. | 0 | — |
| Toray Industries, Inc. | 0 | — |
Where to take this next
The landscape points to specific next steps depending on whether the goal is clearance, licensing or new filing.
Scope a freedom-to-operate check
With no assignee holding more than 3,235 of 360,220 records, a workable FTO review needs to check the ranked leaders individually rather than assume one portfolio controls the space.
Run an FTO scan in EurekaWatch for the lag correction
The 2025-2026 filing counts will revise upward as later publications land; re-check the trend before concluding the plateau is final.
Track filing trends in EurekaTest claims against the thin classes
F25B and F24D carry the lowest class shares in this set, which is where a narrowly drafted new claim is least likely to collide with existing coverage.
Explore white space in EurekaCommon questions on this landscape
The ranked leader in this dataset holds 3,235 of the 360,220 records in scope, with the fifth-placed assignee at 1,807 and tenth place at 1,215. That gradual taper means the field has a clear leader by volume but no single company controlling enough of the space to be a mandatory clearance stop. A practical review should check the top several assignees individually rather than assume one blocks the rest.
Filings rose from 862 in 2017 to a peak of 940 in 2022 and have declined since, reaching 34 in the still-partial 2026 count. Because publication typically lags filing by around 18 months, the last one to two years will revise upward, but the overall shape through the peak year already points to a plateau rather than continued growth. Several major assignees also show flat or -100% year-over-year filing changes in the most recent year recorded.
The core mechanical classes are F25B (refrigeration & heat pumps) and F24D/F24H (domestic and fluid heating), each covering only 0.2-0.3% of the 360,220 records in scope. Much larger shares sit in C02F water & wastewater treatment (0.7%) and B01D separation processes (0.6%), reflecting the breadth of the underlying search terms rather than a heat-pump-specific taxonomy. A record can carry several IPC codes, so these shares are not mutually exclusive and add to more than 100% combined.
The thinnest coverage sits in the core refrigeration-cycle classes themselves — F25B and F24D — relative to the volume of adjacent water-treatment and materials filings that share the same search vocabulary. Specific under-claimed branches include cascade two-stage cycle control logic, compressor discharge temperature correction for variable water content, and the boundary between wastewater heat recovery and refrigeration hardware. These are narrower niches than the broad water-treatment classes but show visibly lower filing density in this dataset.
US6715916B2 claims a control-system method for correcting gas turbine firing and combustion reference temperatures for water content in intake air, using compressor discharge temperature, exhaust gas temperature and turbine pressure ratio as inputs. It is a control-layer patent tied to gas turbine combustion tuning, not a heat exchanger or heat-pump cycle hardware claim, so it constrains a narrow slice of work involving turbine water-content correction rather than water-to-water heat pump design broadly. Anyone building compressor discharge temperature logic for a different application, such as a heat pump cycle rather than turbine combustion, should still review its claim scope directly rather than assume it is out of reach.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.