Summer 2025 was the hottest on record since the Japan Meteorological Agency began statistics, with the average temperature anomaly reaching +2.36°C above the long-term mean. The cumulative number of AMeDAS stations recording extremely hot days (≥35°C) reached 9,385 — more than the 8,821 stations in the prior year. During summer when guests spend longer hours in their rooms, satisfaction is increasingly driven by “how well the AC works.” This article extracts mentions of “room temperature/air conditioning” from guest reviews, aggregates them by hotel format, grade, and building age, and quantifies the impact of cooling on satisfaction — alongside the recovery horizon for AC replacement Capex framed as an opportunity axis.

In an Era of Normalized Extreme Heat — What Are “Room Temperature” Reviews Telling Us

Japan’s summer 2025 (June–August) mean temperature came in at +2.36°C above the long-term average — the highest figure since the statistical series began in 1898. Northern Japan +3.4°C, eastern Japan +2.3°C, western Japan +1.7°C: every region broke records, and 132 of the country’s 153 weather stations logged their hottest summer mean on record (Japan Meteorological Agency). Cumulative AMeDAS stations recording extreme heat days totaled 9,385 — the most in the comparable period since 2010.

This temperature environment directly impacts the lodging experience. Guests spend more time relying on AC in-room, and the satisfaction weight assigned to set-point, airflow, and dehumidification effectiveness has risen. A Japan Weather Association study reported that heatstroke-related emergency transports exceeded 100,000 in 2025 — driving broader social awareness of the importance of indoor thermal environments.

Looking at guest reviews, mentions of room temperature (AC effectiveness, too hot or too cold) accounted for 3.0% of approximately 320,000 reviews in the most recent 3 months, and 4.6% of approximately 1.62 million reviews in the prior 12 months. On an annual scale, the AC mention rate is driven by both winter heating complaints and summer cooling complaints, and seasonal-averaged it tracks around 4–5%. The notable point: among specific clusters of properties, the rate runs 2–3× the industry average. Note that thermal stress affects not only cooling evaluation but also bathing-experience preferences; for the question of which property types are favored in summer reviews, see our detailed analysis in ‘Open-Air Bath’ Mentions Rising Under Extreme Heat.

Source: HotelBank Editorial Team analysis (NLP)

Cooling Evaluation Gap by Format — Business Hotels and Capsules Struggle, Resorts Stable

Aggregating the top 50 properties by room-temperature negative mention volume (N=50, 116,558 reviews) by format reveals a clear gap. Capsule hotels 9.81%, business hotels 7.74%, city hotels 6.62%, resort hotels 5.60%: urban formats with higher room density show higher mention rates. Sample-size constraints apply, but resorts hold relatively low mention rates.

This gap is driven less by raw property quality than by “design generation” differences — whether guest-room windows open, whether AC is individually or centrally controlled, fresh-air intake volume, and thermal-load interference between adjacent rooms. Business hotels carry small rooms and dense layouts, leaving them vulnerable to thermal loads from neighbors above, below, and beside. City hotels, with large-scale building systems, sometimes constrain the freedom of individual control. Resorts, in contrast, typically offer larger rooms with operable windows, which disperses summer thermal stress structurally.

Source: HotelBank Editorial Team analysis (NLP, N=50 properties)

The Counter-Intuitive Link Between Building Age and Cooling Evaluation — “Newness” Isn’t the Whole Story

Building-age aggregation produced a surprising result. Properties under 20 years old — relatively new ones — score 7.41%; 20–40 years old score 7.38%; over 40 years old score 6.72%. Intuitively, older properties should suffer worse from equipment degradation, but the data shows the opposite trend.

Three structural factors plausibly drive this. First, properties over 40 years old often run large centralized mechanical HVAC systems with low temperature variability, while newer small-scale business hotels typically deploy 1-unit-per-room packaged AC (individual control) — and in many cases model selection and capacity sizing are mismatched to room size and insulation performance. Second, properties over 40 years old have often undergone HVAC updates through past renovation cycles — building age does not necessarily equal equipment age. Third, newer properties have tighter window air-sealing, but ventilation and dehumidification controls are often on a separate system from cooling — weak humidity control creates the phenomenon of “feels muggy even at the set temperature.”

Combining building age and format, “under 20 years old × business hotel” emerges as the highest-risk segment. This segment expanded rapidly during the 2015–2020 urban business hotel opening boom. The dominant design approach kept room footprints small to secure ADR competitiveness, but a meaningful share of properties were caught flat-footed on design margin for summer thermal load.

Source: HotelBank Editorial Team analysis (NLP, N=50 properties)

By Grade — Budget/Economy Tiers Show the Highest Negative Mention Rates

By hotel grade: Budget (9.53%) → Economy (7.92%) → Luxury (7.08%) → Upper (6.84%) → High Grade (6.04%). Lower price tiers correlate with higher negative mention rates. This points to a capital-allocation problem: lower-ADR properties operate under tighter per-room HVAC budgets, leading to barely-sufficient capacity sizing and reuse of identical equipment models.

One notable observation: luxury (7.08%) ranks higher than high-grade (6.04%). Sample-bias effects (N=9 properties) may contribute, but an “expectations gap” factor is also plausible — guests at luxury properties carry higher expectations, so even minor temperature discomfort surfaces in reviews. Luxury negative mentions even include “the AC is too strong, the room is too cold,” distinctive to this tier.

Source: HotelBank Editorial Team analysis (NLP, N=50 properties)

Regional Cooling-Evaluation Gap — High Mention Rates in Hokkaido and Tokyo

By prefecture, the room-temperature negative mention rates rank: Tokyo 7.86%, Hokkaido 7.25%, Osaka 6.90%, Fukuoka 6.83%, Okinawa 5.30%, Chiba 5.05%. Surprisingly, Hokkaido ranks second behind Tokyo. Many Hokkaido properties built HVAC capex under the assumption that “Hokkaido summers stay cool” — but in recent years Sapporo’s August mean-maximum temperature has risen approximately 2°C from the 1990s, and equipment capacity has failed to keep up.

Okinawa’s relatively low rate (5.30%) reflects HVAC designed from the outset for heat. Chiba’s low score is partly a sample-composition effect (large-scale city hotels around Narita). The Hokkaido case is emblematic of how climate change is surfacing the need for HVAC Capex investment in “regions previously not expected to need it.”

Source: HotelBank Editorial Team analysis (top 20 properties per prefecture)

Recovery Horizon for AC Replacement Capex — ROI Modeling

For properties carrying high room-temperature negative mention rates, AC replacement offers significant opportunity on both guest-satisfaction improvement and cost reduction. According to METI’s hotel energy-efficiency pamphlet, HVAC accounts for approximately 30% of a hotel’s total electricity consumption. Replacing older units (10+ years) with the latest high-efficiency models is reported to deliver 15–25% reductions in HVAC power consumption, depending on the model. For the broader impact of electricity-price escalation on industry GOP, the structural framework analyzing AC cost models for business hotels and resorts has been published separately.

Per-room individual HVAC replacement Capex varies with model and installation conditions, but the typical industry range is roughly ¥200,000–500,000 per room. Assuming a 200-room business hotel doing full replacement at ¥60 million (¥300,000/room × 200 rooms) and simulating the HVAC-related electricity cost compression effect, the picture is as follows.

Table 1: 200-Room Business Hotel — AC Replacement Capex / ROI Model (Mid Case)

Item	Value (Estimated)	Basis
Room count	200 rooms	Assumption (standard business hotel size)
Capex per room	¥300,000	Mid-range of industry quotes (unit + installation)
Total Capex	¥60 million	200 rooms × ¥300,000
After 1/3 subsidy capture (energy-saving / non-fossil transition)	Approx. ¥40 million	METI “Energy-Saving Investment Promotion Support Project Subsidy (III)”
Annual electricity cost (existing, estimated)	¥24 million	200 rooms × ¥10,000/month × 12 (industry average range)
Of which HVAC (30%)	¥7.2 million	METI hotel energy-saving data
Post-replacement HVAC cost reduction (20%)	¥1.44 million/year	Effect of switching to high-efficiency units
Payback period (with subsidy)	Approx. 28 years	If recovering via electricity savings alone

Purely from electricity-cost reduction, payback runs around 28 years even after subsidy capture — a long horizon. But this is a conservative model recovering “electricity-savings only.” In practice, additional return components stack on top.

• ADR uplift opportunity from review-score improvement — A 3pp drop in room-temperature negative mention rate can lift overall review scores, improve OTA rankings, and open ADR upside of approximately 1–3%.
• Occupancy improvement opportunity — Higher repeat-guest rates and better new-booking conversion can deliver 1–2 points of upside on annual occupancy.
• Summer-peak electricity-rate optimization — Demand control to reduce contracted electricity capacity unlocks additional savings on the fixed-rate portion.
• Reduced breakdown/complaint response costs — Older units carry rising failure risk after 7–10 years, generating emergency-repair costs and revenue loss from temporary room shutdowns. Switching to new units flattens preventive-maintenance costs.

Incorporating these upside elements, effective payback shrinks to 10–15 years. The compounding of recent demand dynamics — post-Expo 2025 Osaka inbound expansion, the 2030 wave of new openings in Hokkaido Niseko — sharpens the competitive structure where “properties differentiated on comfort” win preference.

Source: MetroEngines Research estimates based on METI and Kansai Electric Power public materials (200-room standard business hotel assumption)

Available Subsidy and Support Programs (FY2026 Edition)

Multiple subsidies underpin hotel HVAC replacement in FY2026. Key programs are summarized below.

Table 2: FY2026 Subsidy Programs Available for Hotel HVAC Replacement

Program Name	Subsidy Rate / Cap	Target / Requirements
Energy-Saving Investment Promotion Support Project Subsidy (III) — Equipment-Unit Type	Up to 1/3, cap ¥100M/project, floor ¥300K	Replacement to designated high-efficiency commercial AC units
Acceleration of Decarbonization Retrofits for Commercial Buildings (Decarbonized Building Renovation Project)	Generally 1/3, varies by target	Commercial buildings including hotels; ≥30% primary-energy reduction
SME Labor-Saving Investment Subsidy	Designated labor-saving equipment; range varies by sector	Small- and mid-scale lodging operators; includes HVAC control automation

Subsidies set application windows and budget caps each fiscal year — early submission is advantageous. HVAC replacement also requires factoring in construction lead time. Starting work by early spring (April–May), ahead of the summer peak, lets operators reflect the cooling-performance improvement in the same year’s high season.

Common Traits of High-Scoring Properties

Looking at properties with high positive mentions on room temperature (near-zero negative mentions, 30+ positive mentions), some common patterns emerge. Resorts, newer business hotels, and onsen-town ryokans concentrate positive mentions like “the AC works well and stays comfortable” or “could sleep cool even in summer.”

These properties implement three things at a high level: building in cooling-capacity margin per room, automatic switching to dehumidification mode via humidity sensors, and quiet operation. Humidity control in particular is easily overlooked but significantly shapes a guest’s perceived temperature. The latest high-efficiency units integrate dehumidification, ventilation, and cooling control — so raising the set-point by 1°C still feels cool, and power consumption drops as a result.

Conclusion — In the 40°C Heatwave Era, Guest-Room HVAC Shifts from “Cost Center” to “Revenue Opportunity”

The record summer of 2025 forced the industry to confront a climate-change-driven “shift in baseline temperature.” With 2026 and onward likely matching or exceeding that heat as the new normal, it is time to rethink the design of guest-room HVAC. Implications from this analysis:

• The room-temperature negative mention rate runs around 4–5% industry-wide, and 7.13% in the top 50 properties. By format: capsule and business hotels score high. By grade: budget and economy. By region: Tokyo and Hokkaido. A consistent structural pattern emerges.
• Beyond age, design-generation factors — room size, insulation, humidity control, and individual vs. central HVAC — drive satisfaction. Even under-20-year-old business hotels include a meaningful share of properties with insufficient design margin.
• AC replacement Capex runs about ¥300,000/room. Recovery from electricity savings alone takes a long horizon — but bundling ADR / occupancy upside from review-score improvement compresses effective payback to 10–15 years.
• FY2026 subsidies (Energy-Saving Investment Promotion Support, Decarbonized Building Renovation) cover 1/3 of Capex. Starting work in early spring lets the improvement land in time for the summer peak.
• Guest-room HVAC is no longer a pure cost-reduction target — it is a positioning investment that differentiates guest experience and generates revenue. With extreme heat normalizing through 2026 and beyond, “a hotel with AC that works” is a clear competitive advantage.

Room-temperature mentions are one of the few signals that surface the “quality of comfort” — something guests rarely articulate explicitly. Monitoring patterns of thermal stress in OTA reviews lets operators make objective decisions on replacement timing and priority. As the lodging industry’s competitive axis evolves in the climate-change era, “room temperature quality” is set to grow steadily in importance.