Efficiency-weighted cooling degree days reveal opposing temperature and humidity effects on energy demand

Efficiency-weighted cooling degree days reveal opposing temperature and humidity effects on energy demand | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Physical Sciences - Article Efficiency-weighted cooling degree days reveal opposing temperature and humidity effects on energy demand Jake Casselman, Christina Karamperidou This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8683958/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Cooling degree days (CDD) are widely used to estimate air-conditioning energy demand, yet they implicitly assume constant refrigeration efficiency neglecting its strong dependence on temperature and humidity. Here, we introduce an efficiency-aware cooling metric --effective cooling degree days (eCDD)-- that links ambient temperature and humidity conditions to the physical work required for cooling. Applying this framework across North America, we show that cooling efficiency has declined by 2–4% per decade since 1971, and that regionally opposing trends in temperature and humidity cause CDD to misrepresent cooling demand. During hot extremes, efficiency losses are amplified under humid-heat conditions but partially offset under dry-heat conditions. Projections further reveal a continent-scale shift in humidity regimes, with an eastward extension of dry heat that locally enhances cooling efficiency during extremes, even as eCDD increases by 10–80% across the continent. These results demonstrate that temperature-based metrics alone are insufficient and that efficiency-aware metrics such as eCDD are essential for accurately assessing cooling demand, especially considering differing electricity generation mixes. Earth and environmental sciences/Climate sciences/Atmospheric science Earth and environmental sciences/Environmental sciences/Environmental impact Cooling degree days Coeffcient of performance Sensible heat ratio Humid-heat extremes North American climate projections Full Text Additional Declarations There is NO Competing Interest. Supplementary Files ExtendedData.pdf Extended Data Figs. 1–9 Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8683958","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":587132340,"identity":"16dfe243-f3b5-4404-a121-21b4841558bc","order_by":0,"name":"Jake Casselman","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyklEQVRIiWNgGAWjYBACxgY2EGWTACIPJIAEiNSSRoIWBgawlsMJCDMIaWBuP5b4mKfmfB7/jOSHBx4w2MhuOEDIYT1ph415jt0ulriRZgB0WJoxYS0N6W3SuQ23ExtuJ4C0HE4krKX/efvv3IZzifNvp38AavlPhJYZaceYcxsOJG64nQOy5QAxWp4lS/85lpy48f6bggMJBsnGMwlpMexPM/w4o8Yucd6Z45s//qiwk+0jqKUBhWtAQDkIyBOhZhSMglEwCkY6AACUNk8uCwWM/gAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0003-2525-8422","institution":"University of Hawaiʻi at Mānoa","correspondingAuthor":true,"prefix":"","firstName":"Jake","middleName":"","lastName":"Casselman","suffix":""},{"id":587132341,"identity":"ce9c2071-0bab-4db6-9089-ebc564f23ece","order_by":1,"name":"Christina Karamperidou","email":"","orcid":"","institution":"University of Hawaiʻi at Mānoa","correspondingAuthor":false,"prefix":"","firstName":"Christina","middleName":"","lastName":"Karamperidou","suffix":""}],"badges":[],"createdAt":"2026-01-24 05:25:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8683958/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8683958/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102964083,"identity":"ac4de7d7-71e4-4c53-8322-935bfbb4f74a","added_by":"auto","created_at":"2026-02-19 04:21:25","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":14166317,"visible":true,"origin":"","legend":"Article File","description":"","filename":"MainManuscriptLined.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8683958/v1_covered_f88a381f-f985-41d3-b495-5fcf1fc61da8.pdf"},{"id":102895788,"identity":"785e60bf-c3fc-4baf-8e76-26c024f9c1d5","added_by":"auto","created_at":"2026-02-18 06:28:50","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":67554066,"visible":true,"origin":"","legend":"Extended Data Figs. 1\u0026#x2013;9","description":"","filename":"ExtendedData.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8683958/v1/4dc8b060e596cd9823ba4576.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Efficiency-weighted cooling degree days reveal opposing temperature and humidity effects on energy demand","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Cooling degree days, Coeffcient of performance, Sensible heat ratio, Humid-heat extremes, North American, climate projections","lastPublishedDoi":"10.21203/rs.3.rs-8683958/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8683958/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Cooling degree days (CDD) are widely used to estimate air-conditioning energy demand, yet they implicitly assume constant refrigeration efficiency neglecting its strong dependence on temperature and humidity. Here, we introduce an efficiency-aware cooling metric --effective cooling degree days (eCDD)-- that links ambient temperature and humidity conditions to the physical work required for cooling. Applying this framework across North America, we show that cooling efficiency has declined by 2–4% per decade since 1971, and that regionally opposing trends in temperature and humidity cause CDD to misrepresent cooling demand. During hot extremes, efficiency losses are amplified under humid-heat conditions but partially offset under dry-heat conditions. Projections further reveal a continent-scale shift in humidity regimes, with an eastward extension of dry heat that locally enhances cooling efficiency during extremes, even as eCDD increases by 10–80% across the continent. 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