The dataset covering 2015 through the 2026 cut-off contains 155 published patent families that combine absorption chiller, absorption refrigeration or absorption cooling terminology with absorption heat pump IPC classification (F25B15/00, F25B30/04, F25B27/00). This counts families rather than raw documents, which is the fairer unit because it neutralises duplicate filings across jurisdictions and continuation applications from the same invention. It is not a count of commercially deployed systems, only of patent protection sought.

Filing activity is accelerating, not shrinking. Annual filings were at 2 in 2017, fell to 0 at the 2022 midpoint, and have since risen to a peak of 6 in 2025. Because patent publication typically lags the filing date by around 18 months, the most recent year in any such trend is always undercounted, so the actual 2025-2026 filing volume is likely higher than currently visible.

F25B (refrigeration and heat pump machinery) anchors every record in this set by definition of the search. Beyond that core, C09K (materials for miscellaneous applications, largely working-fluid and sorbent chemistry) is the clear second subclass at 42 records, indicating that fluid-pair and sorbent formulation is where most technical differentiation is being claimed. Air conditioning integration (F24F), heat exchangers (F28D), water heating (F24H), separation processes (B01D), water treatment (C02F) and pump design (F04B) each account for single-digit to low-double-digit shares, marking those as narrower, less contested claim spaces.