EcoFactor v. Google & ecobee: Federal Circuit Affirms Unpatentability of Thermal Mass Patent
EcoFactor, Inc. asserted US8751186B2 — covering a system and method for calculating a building’s thermal mass — against Google and ecobee Technologies. After 637 days before the Federal Circuit, the court affirmed the patent’s unpatentability, a decisive outcome for both smart thermostat defendants.
Federal Circuit closes the door on EcoFactor’s building thermal mass claim
EcoFactor, Inc. filed appeal case 24-1027 at the Court of Appeals for the Federal Circuit on 10 October 2023, challenging a finding that US8751186B2 was unpatentable. The patent, directed to a system and method for calculating the thermal mass of a building, sits at the intersection of smart-home energy management and HVAC control — technology directly relevant to products commercialised by both Google (Nest) and ecobee Technologies.
The Federal Circuit issued its judgment on 8 July 2025, ordering the lower determination affirmed. An affirmance on patentability grounds means the court found no reversible error in the tribunal below’s invalidity or cancellation analysis. For EcoFactor, the asserted patent is effectively extinguished as an enforcement tool against Google and ecobee. Both defendants can continue operating without licence obligations tied to US8751186B2.
The 637-day duration suggests full appellate briefing and likely oral argument before disposition — not a summary or procedural dismissal. The basis of termination recorded as ‘Unpatentable’ is consistent with an inter partes review or post-grant proceeding that EcoFactor unsuccessfully appealed. The public record does not disclose the specific claim-level arguments or claim construction positions that drove the outcome, but the unambiguous affirmance leaves limited appellate runway for EcoFactor beyond a petition for certiorari.
Filing to Unpatentable in 637 days
637 days at appeal level — consistent with a fully briefed Federal Circuit patentability proceeding
Federal Circuit affirms: what the unpatentability ruling means for both parties
What ‘AFFIRMED’ means at the Federal Circuit
An affirmance by the Federal Circuit means the panel reviewed the lower tribunal’s unpatentability determination and found no reversible legal error. The court applies a deferential standard to factual findings — such as anticipation or obviousness — and reviews claim construction de novo. An affirmed unpatentability ruling is final at this level; US8751186B2 cannot be enforced based on the challenged claims.
No reversible error foundEcoFactor loses enforcement rights over US8751186B2
The affirmance extinguishes EcoFactor’s ability to assert the challenged claims of US8751186B2 against Google, ecobee, or any third party. With the patent declared unpatentable and that ruling upheld, any licensing programme built around this specific patent is effectively foreclosed. EcoFactor’s remaining options are narrow: a petition to the Supreme Court for certiorari, which is rarely granted, or pursuing other patents in its portfolio.
Patent unenforceableGoogle and ecobee secure freedom to operate
For Google and ecobee, the affirmance confirms that the thermal mass calculation patent cannot be wielded against their smart thermostat platforms. The Federal Circuit ruling creates a strong precedent record: any future attempt by EcoFactor to relitigate equivalent claims faces a high collateral estoppel bar. Both defendants’ HVAC and energy-management product lines are insulated from this specific patent threat at the highest appellate level short of the Supreme Court.
Appellate options exhaustedStrengthened prior art landscape for smart thermostat IP
The ruling contributes to a growing body of Federal Circuit authority scrutinising smart-home energy management patents. Companies developing building thermal modelling, predictive HVAC control, or energy optimisation systems can treat the invalidated claims as clarifying prior art boundaries. For patent holders in this space, the case signals that broad thermal-mass calculation claims face a rigorous patentability bar — particularly in post-grant proceedings reviewed by the Federal Circuit.
Higher bar for thermal-mass claimsFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | EcoFactor, Inc | Company | Smart-home energy IP licensor — holder of US8751186B2 covering building thermal mass calculationSearch in Eureka ↗ |
| Defendant | Google, LLC | Company | Google, LLC (Nest smart thermostats) and ecobee Technologies, ULC (smart thermostat manufacturer)Search in Eureka ↗ |
| Co-Defendant | ecobee Technologies, ULC | Company | Search in Eureka ↗ |
| Plaintiff counsel | James Pickens | Attorney | Counsel for EcoFactor, IncSearch in Eureka ↗ |
| Plaintiff counsel | Kristopher Davis | Attorney | Counsel for EcoFactor, IncSearch in Eureka ↗ |
| Plaintiff counsel | Matthew Aichele | Attorney | Counsel for EcoFactor, IncSearch in Eureka ↗ |
| Plaintiff counsel | Philip Wang | Attorney | Counsel for EcoFactor, IncSearch in Eureka ↗ |
| Plaintiff counsel | Reza Mirzaie | Attorney | Counsel for EcoFactor, IncSearch in Eureka ↗ |
| Plaintiff law firm | Russ August & Kabat LLP | Law Firm | Representing EcoFactor, IncSearch in Eureka ↗ |
| Defendant counsel | Elizabeth Laughton | Attorney | Counsel for Google, LLCSearch in Eureka ↗ |
| Defendant counsel | Matthew A. Smith | Attorney | Counsel for Google, LLCSearch in Eureka ↗ |
| Defendant law firm | Smith Baluch LLP | Law Firm | Representing Google, LLCSearch in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | Court of Appeals for the Federal CircuitSearch in Eureka ↗ |
Official order — verbatim text
The Federal Circuit’s order — ‘AFFIRMED’ on a basis of unpatentability — is unambiguous in scope: the lower tribunal’s cancellation or invalidity determination survives appellate review in full. The court’s standard of review applies deference to factual findings (substantial evidence) while reviewing legal conclusions de novo. An unqualified affirmance, without remand, signals the panel found no error warranting further proceedings. EcoFactor retains no live claim under US8751186B2 as a result of this ruling.
US8751186B2 — System and method for calculating the thermal mass of a building
US8751186B2 (application number US13/858710) protects a system and method for calculating the thermal mass of a building — a parameter that quantifies how much heat energy a structure absorbs and retains over time. Thermal mass is a foundational variable in predictive HVAC control: accurate estimation enables a thermostat or energy-management system to pre-condition a space more efficiently, reducing energy consumption and improving comfort. The patent sits within the broader smart-home and building automation domain, an area that has attracted significant IP activity as connected thermostat platforms have scaled commercially.
The patent’s strategic significance lies in its position upstream of thermostat intelligence: any system that models building heat dynamics to inform HVAC scheduling arguably touches the claimed methods. This made it a broadly applicable assertion tool against major smart thermostat platforms, including Google Nest and ecobee. The Federal Circuit’s affirmance of unpatentability — likely following a PTAB post-grant proceeding — effectively removes this patent as a licensing or litigation asset and may inform how examiners and tribunals evaluate similar algorithmic building-physics claims going forward.
Should your team run an FTO against US8751186B2?
R&D and product teams developing predictive HVAC control systems, smart thermostats, building energy management platforms, or any software that estimates thermal properties of structures should be aware that US8751186B2 has been declared unpatentable and that ruling has been affirmed by the Federal Circuit. While this patent no longer poses a direct enforcement risk from EcoFactor, related continuation patents or divisional applications in the same family may cover overlapping technical ground and remain active.
PatSnap Eureka’s FTO Search Agent can map the full EcoFactor patent family around thermal mass calculation and building energy modelling, identify any surviving related claims, and flag prior art that informed the invalidity outcome. For teams commercialising predictive HVAC or building-physics algorithms, a targeted FTO review against the EcoFactor portfolio — and comparable smart-home energy management patent families — provides the clearest path to defensible freedom to operate.
Run a freedom-to-operate analysis on US8751186B2 to assess your product’s exposure
Run FTO in Eureka →Similar Federal Circuit cases: smart-home and building energy management patent disputes
Cases before the Federal Circuit involving patentability challenges to building energy management and smart thermostat technology — comparable to EcoFactor v. Google.
What this case signals for the smart-home energy IP landscape
The affirmance reinforces Federal Circuit scrutiny of algorithmic building-energy patents and has direct implications for HVAC and smart thermostat IP strategy.
Post-grant proceedings remain a potent weapon against energy-management patents
The unpatentability basis and subsequent Federal Circuit affirmance suggests the invalidity challenge succeeded at the PTAB or equivalent tribunal level. For defendants in smart-home and HVAC litigation, this case reinforces that IPR or PGR proceedings targeting algorithmic energy-management claims can yield durable, appellate-proof outcomes.
EcoFactor’s portfolio strategy warrants ongoing monitoring by thermostat OEMs
With US8751186B2 effectively cancelled, competitors and licensees should audit EcoFactor’s remaining patent family for continuations or divisionals covering thermal modelling or predictive HVAC control. Patent families often contain related claims that survive even when one patent is invalidated, and a licensing entity with this profile typically holds multiple related assets.
EcoFactor v Google — key questions answered
The Federal Circuit affirmed the unpatentability of US8751186B2 on 8 July 2025. The order — ‘AFFIRMED’ — means the lower tribunal’s cancellation or invalidity determination was upheld in full, with no remand. EcoFactor cannot enforce the challenged claims against Google, ecobee, or any other party.
US8751186B2 covers a system and method for calculating the thermal mass of a building — a parameter used in predictive HVAC control to estimate how a structure absorbs and retains heat. EcoFactor asserted it against Google (Nest) and ecobee because both companies’ smart thermostat platforms use building-physics modelling to optimise heating and cooling schedules, which falls within the scope of the claimed methods.
A ‘basis of termination: unpatentable’ at the Federal Circuit appeal level typically indicates the court reviewed a lower tribunal’s determination — most likely from the USPTO Patent Trial and Appeal Board in an IPR or PGR proceeding — that one or more claims of the patent lacked novelty or were obvious over prior art. The Federal Circuit’s affirmance means that determination was found free of reversible error.
EcoFactor’s practical appellate options after a Federal Circuit affirmance are very limited. The primary avenue is a petition for a writ of certiorari to the U.S. Supreme Court, which grants review in a very small fraction of cases. Absent certiorari, the Federal Circuit’s ruling is final, and US8751186B2’s unpatentability is settled law.
The Federal Circuit’s affirmance clarifies that the thermal mass calculation claims in US8751186B2 are unpatentable, removing a direct licensing threat. However, companies in the smart-home energy space should audit EcoFactor’s broader patent portfolio for surviving continuation or divisional patents covering related technology, as a licensing entity typically holds multiple related assets that may remain active and enforceable.
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