Heat Pump Charge Optimization Patents: Leader & Long Tail 2026
- One filer dominates. The leading assignee alone accounts for 156 of 298 records in scope — the rest of the ranked field trails far behind.
- Concentration is extreme at the top. The top 5 assignees combine for 84.6% of all 298 records, and the top 10 reach 93.0% — very little activity sits outside a handful of players.
- Filing has cooled sharply since the peak. Filings fell from 20 in 2021 to 2 in 2024, a 90% drop over that span, after peaking at 76 in 2017.
Filing growth compares 2021 (20 records) with 2024 (2) — 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 298 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This landscape tracks patent activity at the intersection of refrigerant charge management and heat pump / vapor-compression systems — filings that claim charge estimation, charge control valves, superheat and subcooling strategies, or charge-optimization logic within a refrigerant circuit. The scope spans 298 published records filed between 2015 and the 2026 data cut-off, drawn from major receiving offices including the United States, the EPO, Canada, WIPO and India.
The dataset sits closer to a mechanical-controls niche than a broad HVAC category: classification density clusters around refrigeration and heat-pump circuitry, with meaningful overlap into turbine and thermal power-plant classes that reflects shared compressor and heat-exchange components rather than a separate technology thread.
Filing trend and technology composition
Two views of the same 298-record set: how filing volume has moved year over year, and which IPC subclasses the claims fall into.
Filing trend
Filings peaked at 76 in 2017 and have declined since; 2021 to 2024 alone saw a drop from 20 to 2 filings, a 90% fall over three years. Because publication typically lags filing by around 18 months, 2025 and 2026 figures are still incomplete and should not be read as confirmation that the decline continues at this pace.
Technology composition
F25B (refrigeration & heat pumps) covers 48.0% of the 298 records, the largest single class, followed by F01K (steam & thermal power plants) at 41.3% and F02C (gas-turbine plants) at 37.2%. Because records can carry multiple IPC codes, these shares sum to well over 100%; the overlap between refrigeration classes and turbine/power-plant classes points to shared compressor and control architectures rather than distinct sub-fields.
Shares are the percentage of the 298 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Heat Pumps — Heat-Pump Refrigerant-Charge Optimization Patent Landscape with Eureka
This page is one run against one query. Ask Eureka your own question about heat pumps — heat-pump refrigerant-charge optimization patent landscape and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited prior art in this space
US4484452A — Heat pump refrigerant charge control system
A microcomputer-controlled charge control system modulates refrigerant charge in a heat pump circuit using a charge receiver in thermal communication with the compressor suction line, connected via a charge control valve to a point between two controllable expansion valves. Superheating and subcooling strategies maintain the charge at optimum levels, automatically adapting to changing environmental load on the heat exchange coils, with additional control logic to shift charge as conditions vary.Filed 1984 — among the earliest and most-cited records in this dataset, cited 117 times.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US20150260463A1 | Systems and methods for energy storage and retrieval | 169 |
| 2 | US4299098A | Refrigeration circuit for heat pump water heater and control therefor | 121 |
| 3 | US20060042276A1 | System and method for detecting decreased performance in a refrigeration system | 119 |
| 4 | US4484452A | Heat pump refrigerant charge control system | 117 |
| 5 | US4399664A | Heat pump water heater circuit | 98 |
| 6 | US20180179917A1 | Variable Pressure Inventory Control of Closed Cycle System with a High Pressure Tank and an Intermediate Pres… | 92 |
| 7 | US4646537A | Hot water heating and defrost in a heat pump circuit | 88 |
| 8 | US4528822A | Heat pump refrigeration circuit with liquid heating capability | 85 |
| 9 | WO2014052927A1 | Systems and methods for energy storage and retrieval | 82 |
| 10 | US5771700A | Heat pump apparatus and related methods providing enhanced refrigerant flow control | 81 |
Citation counts accumulate over time and favour older filings; they signal influence on later filings, not current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
Put your own technology through the same analysis
Eureka on the web
When you want the answer in the next five minutes.
The agent works the prompt against patents and technical literature, citing every source.
Run your analysis now →MCP server & REST API
When it has to run inside your own pipeline.
Patent search, landscape analysis and assignee resolution as MCP tools. Drop them into any agent framework, or call REST directly.
Browse MCP servers →What the numbers mean for a filing strategy
Reading concentration, timing and classification together points to where claim space is occupied and where it likely is not.
A small group holds most of the claim space
The top 5 assignees combine for 84.6% of all 298 records and the top 10 reach 93.0%. With the ranked leader alone holding 156 records, most of the practical charge-control art in this dataset has already been claimed by a handful of organisations, leaving the remaining 39 ranked companies with single-digit counts each.
Filing has cooled well off its 2017 peak
Activity peaked at 76 filings in 2017 and fell steadily; the 2021-to-2024 window alone shows a 90% decline from 20 to 2 filings. That trajectory suggests the core mechanical charge-control approaches were substantially claimed earlier in the period, with newer filings increasingly narrow or defensive.
Refrigeration claims overlap heavily with turbine and power-plant art
F25B (refrigeration & heat pumps) appears in 48.0% of records, but F01K (steam & thermal power plants, 41.3%) and F02C (gas-turbine plants, 37.2%) are also heavily represented. This overlap reflects shared compressor, expansion-valve and heat-exchange control logic rather than a genuinely separate application area.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to heat pumps — heat-pump refrigerant-charge optimization patent landscape, with the prior art for and against each one.
Who holds the ground, and where the gate stands open
One assignee's filing volume dwarfs the rest of the ranked field, and the co-filing pattern suggests joint development work concentrated among a small set of related entities.
The leading assignee's filing volume sets the field
At 156 of 298 records, the top-ranked assignee's portfolio is more than five times larger than the fifth-place holder's 6 records. Any new entrant should expect the leader's claims to define the boundaries of core charge-control mechanisms.
Most ranked assignees hold only a handful of filings
Beyond the top 10 assignees, who together account for 93.0% of all 298 records, the remaining ranked companies each hold only a small number of filings. This is a field with a dominant core and a thin, fragmented periphery rather than a broad competitive middle.
Co-filing clusters around a few related entities
Ten co-assignee pairs appear in the dataset, with the strongest links (each appearing 6 times) connecting the leading corporate assignee to related corporate and individual co-filers. This points to sustained joint development rather than incidental co-ownership.
| Assignee | Recent year | YoY |
|---|---|---|
| Malta Inc. | 0 | — |
| Carrier Corp | 0 | — |
| X Development LLC | 0 | — |
| Springer Carrier | 0 | — |
| TESCHE CARLOS AFONSO | 0 | — |
| MURAKAMI TOSHIO | 0 | — |
| FERNANDEZ ROBERTO GUSTAVO | 0 | — |
| York International Corp | 0 | — |
Where to take this analysis
The dataset points to a mature core with a narrow gate still open. The next steps depend on whether the goal is freedom-to-operate or new claim drafting.
Map claims against the leader's portfolio
With one assignee holding 156 of 298 records, a freedom-to-operate review should start by mapping any planned charge-control mechanism against that portfolio specifically, not the field broadly.
Explore assignee portfolios in EurekaTest the under-claimed control branches
G05D-classified control logic and F28D heat-exchange interfaces show lower filing density than the core F25B claims, suggesting room for narrowly drafted claims in those branches.
Run a white-space search in EurekaWatch for renewed filing activity
The 2021-2024 decline is based on complete-year data; because publication lags filing by about 18 months, a rebound in 2025-2026 filings would not yet be visible in this trend.
Set a filing alert in EurekaCommon questions about this patent landscape
The ranking in this dataset of 298 records is led by a single assignee holding 156 records, far ahead of the rest of the field. The top 5 assignees combine for 84.6% of all records and the top 10 reach 93.0%, meaning the remaining 39 ranked companies each hold only a small number of filings. Anyone assessing competitive position in this space should treat the leader's portfolio, not the field average, as the benchmark.
Filings peaked at 76 in 2017 and have declined since, with complete-year data showing a fall from 20 filings in 2021 to 2 in 2024 — a 90% drop over that span. However, because patent publication lags filing by roughly 18 months, the 2025 and 2026 figures in this dataset are still incomplete and should not be read as proof the decline is ongoing at that rate. A clearer read on the most recent years will only be available once those cohorts finish publishing.
US4484452A claims a microcomputer-controlled system that modulates refrigerant charge via a charge receiver and charge control valve positioned between two expansion valves, using superheat and subcooling strategies to hold charge at optimum levels as load conditions change. Filed in 1984 and cited 117 times within this dataset, it represents a foundational architecture for active charge control rather than a narrow point claim. New designs that route charge through a similar receiver-and-valve arrangement with adaptive superheat/subcooling logic should be checked against this and related early filings before assuming freedom to operate.
The IPC composition shows heavy overlap between core refrigeration and heat-pump classification (F25B, 48.0% of records) and turbine or power-plant classes such as F01K (41.3%) and F02C (37.2%). This reflects shared compressor, expansion-valve and heat-exchange control mechanisms across refrigeration and power-generation equipment rather than genuinely separate technical fields. Filers targeting charge-control claims should expect examiners to cite art from these adjacent classes.
Classes with comparatively lower record counts in this dataset, such as G05D (control of non-electric variables, 5.7% of records) and F28D (heat-exchange apparatus, 9.4%), show less claim density than the core F25B refrigeration class. That does not guarantee an easy grant, but it does suggest narrower competitive crowding for claims combining charge-control logic with these adjacent control or heat-exchange mechanisms. A targeted search against the leading assignee's specific claim language is still the necessary next step before drafting.
Research Heat Pumps — Heat-Pump Refrigerant-Charge Optimization Patent Landscape in depth with Eureka
Go past this page: query the whole heat pumps — heat-pump refrigerant-charge optimization patent landscape corpus yourself, in your own scope.
Every answer comes back with patent numbers you can open.
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.