How to assess hotel emissions data for corporate reporting

The UK government's 2026 emission factors for hotel stays are the same numbers it published in 2022, and they rest on hotel data from 2019. The 2026 conversion factors methodology paper lists the hotel stay factors among those held constant from the 2022 release. For a night in the United States, that factor is 16.1 kg of CO2 equivalent (CO2e) per room.

The free tool those factors were taken from is updated annually and is now on 2024 data. It gives 14.0 kg for a US room night, or 22.5 kg if you tell it the hotel was four-star.

All three numbers follow a published method. For corporate reporting, which one belongs in your inventory comes down to four checks: the data year, the hotel class, the electricity method and what a room night covers. There are also a few questions to ask the hotel or travel supplier that gave you the figure.

Where hotel emissions figures come from

You'll be offered four kinds of figure. Three trace back to the same method, the Hotel Carbon Measurement Initiative (HCMI):

• The hotel's own figure. HCMI is a free method a hotel uses to work out its carbon footprint per occupied room. The Sustainable Hospitality Alliance, which runs it, says more than 30,000 hotels use it.
• The Hotel Footprinting Tool. Each year the Cornell Hotel Sustainability Benchmarking Index collects data from hotel companies and calculates HCMI figures from it. Its 2026 edition covers more than 31,500 hotels. Greenview, Cornell's partner on the index, publishes the medians by country, region and star class in this free tool.
• The UK government factors. These take one median per country from an earlier version of that tool.
• A spend-based factor. The US EPA publishes a factor per dollar of hotel spend, covering the hotel and what it buys.

1. The year behind the factor

A factor set labeled 2026 can carry much older hotel data. The UK paper credits its hotel factors to the Cornell index's 2021 edition, and the 2021 Cornell index report analyzed 2019 calendar-year data from 21,432 hotels. A company applying the UK's 2026 factors to this year's travel is describing hotels as they ran seven years ago.

Greenview's Hotel Footprinting Tool is on its 2026 version, built on 2024 data, with the next update due in the first quarter of 2027. For the US it gives 14.0 kg per room night against the UK set's 16.1, which is 13% lower. The two figures come from different years and different groups of hotels, so read the gap as a change in the data. It isn't a measured 13% cut in US hotel emissions.

A figure that comes straight from a hotel is fresher. HCMI gives a hotel six months after its reporting year to calculate the footprint, and the result is valid for 12 months. In the method's words, the data "is never more than 18 months old during normal operations."

2. Hotel class: one average or a star rating

The UK factors are, in the government's words, "for an average class of hotel and can be applied to a stay at any type of hotel." One number covers a budget hotel and a resort. The paper also warns that the factors are "skewed toward large, more upmarket hotels and to branded chains."

The Footprinting Tool splits each country by star class. For the US it gives 12.2 kg per room night at two-star hotels, 14.3 at three-star, 22.5 at four-star and 35.5 at five-star. A five-star night counts for 2.9 times a two-star night. In the UK the ratio is 4.25, from 4.8 kg to 20.4.

Take 1,000 US room nights in four-star hotels. The all-hotels figure reports 14.0 tonnes. The four-star figure reports 22.5 tonnes for the same trips, which is 61% more.

Even a star class is a rough guide. In the Cornell index's 2026 dataset, 977 four-star US hotels have a mean of 23.8 kg per room night (the tool's 22.5 is the median), and the individual hotels run from 1.4 kg to 88.5 kg. If a handful of hotels take most of your nights, their own figures will tell you more than any average.

3. How the electricity was counted

A hotel that buys renewable energy certificates reports lower emissions under the market-based method, which counts what the hotel bought, than under the location-based method, which uses the local grid average.

HCMI's methodology introduction allows either, says hotels buying renewable electricity should use market-based, and notes that its calculation tool "uses market-based emissions" by default. The Cornell index's public dataset, which feeds the Footprinting Tool, uses location-based factors throughout. So a hotel that buys certificates can hand you an HCMI figure below the benchmark for an identical building.

Ask which method a figure uses before you compare it with anything. One rule is fixed either way: under HCMI, a hotel that buys carbon offsets "cannot deduct the amount of emissions that is offset" from its total.

4. What a room night covers

An HCMI figure covers the energy used on the hotel's premises, including restaurants, spas and back of house, plus refrigerant leaks and outsourced laundry. It leaves out the food and supplies the hotel buys, its waste, and how guests got there. The Alliance's own buyer guidance says "there is not yet an industry accepted way to measure scope 3 emissions of hotels."

Before you multiply by nights, check three things:

• Meeting space is separate. HCMI splits a hotel's emissions between guest rooms and meeting space by floor area, and reports meetings per square meter per hour. A conference needs both figures.
• "Per occupied room" has two meanings. The Cornell index publishes the HCMI room figure and also a whole-property figure divided by occupied rooms, which includes the meeting space. Check which one a hotel is quoting.
• The unit is the room. The UK guidance says its factor "does not differentiate for number of travellers staying in the room," so two colleagues sharing a room count once.

The UK hotel factors also have no well-to-tank component, meaning the emissions from producing the fuel and power. The same factor set does publish one for flights, so check that your flight and hotel figures cover the same ground.

When all you have is spend

The EPA's GHG Emission Factors Hub has business travel factors for cars, rail, buses and flights, and nothing per night for hotels. What the EPA does publish is a supply chain emission factor for hotels and motels: 0.145 kg of CO2e per dollar, in 2022 dollars (version 1.3).

So $1,000 of US hotel spend comes to 145 kg, the same as about 10 room nights at the Footprinting Tool's US figure.

A spend factor moves with room prices, so the same stay reports more in an expensive city or a busy week. The EPA recommends adjusting the dollar year to match your spend. The factor also covers more ground, because it includes the hotel's suppliers, which a room-night figure leaves out. Use it where you know the spend and can't get the nights, and say that you did.

Which hotel figure to use

The Footprinting Tool lists an all-hotels figure for 250 countries and territories, and marks only 79 of them "Actual." The rest are estimates, 134 of them based on a global figure. The tool shows the method next to each number.

What to ask a hotel or travel supplier

1. Is this figure from the hotel itself or from a benchmark? If it's a benchmark, which version and data year?
2. Does it follow HCMI? Is it the room figure, or the whole property divided by occupied rooms?
3. Is the electricity location-based or market-based? If market-based, which certificates or contracts are behind it?
4. Which 12 months does it cover, and was that a normal year? HCMI tells hotels to fall back on the most recent normal period when energy use swings by 20%.
5. Has anyone outside the hotel checked it?
6. For a benchmark: does it match the hotel's star class, and is it actual or extrapolated?

Question 5 matters because neither the method nor the benchmark requires an outside check. HCMI "only recommends an internal review process and does not mandate external verification," and the UK paper says its hotel data "have not been verified." Assured data does exist: in the Cornell index's 2025 report, about 20% of member companies, covering roughly 71% of the hotels, had their data externally assured to ISO 14064.

For the wider set of questions to send airlines and booking platforms as well, see our travel supplier climate questionnaire.

How to state your hotel emissions method in the report

The GHG Protocol's current guidance on business travel makes hotels optional: companies "may optionally include emissions from business travelers staying in hotels." So the first thing a reader of your report needs to know is whether hotel stays are in it at all.

Then state the method in one sentence. For example:

Hotel emissions are calculated per room night using [source, version and data year], by [country / country and star class / property], with [location-based / market-based] electricity. Meeting space is [included / excluded].

When you move to a newer source, it's good practice to apply it to earlier years as well, so the trend compares like with like. Otherwise a switch from 16.1 kg to 14.0 kg shows up as a 13% cut that may be nothing more than a newer dataset.

For flights, see our guide to assessing airline emissions data. For the rest of the inventory, see our guide to calculating business travel emissions.

Ask us the same questions

Dyme for Business shows an emissions estimate when a traveler books. We use grid emissions data as a proxy, because electricity use is the largest part of a hotel's emissions. Treat it as an electricity-based estimate and put it through the same four checks before it goes in a report.

We also put part of the commission we earn on each booking into solar on schools, clinics and community buildings. That funding isn't an offset, and it doesn't lower the hotel line in your inventory. You report the stay in full either way. Our page on how we calculate Dyme's renewable energy impact shows the math.