Carbon Footprint of Microsoft Outlook
IdleForest models one hour of Microsoft Outlook use at about 10g of CO2.
Outlook combines email, calendar, search, attachments, notifications, and background syncing across desktop and mobile, giving it a small but steady daily footprint.
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How this Outlook estimate is built
IdleForest models Outlook as a lightweight but always-synced work app, slightly above simple email because calendar, attachment, and desktop-client activity are often bundled into the same session.
- The 10gCO2e/hour estimate reflects active email and calendar use rather than idle background sync.
- The yearly estimate uses 10gCO2e/hour x 1 hour/day x 365 / 1000 = 3.7kgCO2e/year.
- Tree offset math rounds 3.7kgCO2e/year divided by 20kgCO2e per tree-year up to 1 tree.
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How the estimate is calculated
Annual footprint formula
10g CO2e/hour x 1h/day x 365 / 1000 = 3.7kg CO2e/year
Tree offset formula
ceil(3.7kg CO2e / 20 kg CO2e per tree-year) = 1 rounded up
Source basis: This estimate combines the app's modeled hourly footprint, usage assumption, methodology notes, and linked research sources. It is directional and should be read as a transparent consumer estimate, not a vendor emissions disclosure.
What drives this estimate most
- Video, screen sharing, and participant count all change the intensity of online work tools.
- Background browser and app activity can keep the system drawing power even outside meetings.
- Meeting-heavy workflows create both device-side and network-side overhead.
Assumptions and boundaries
- The estimate reflects active use rather than an app left open but unused.
- It is built to compare common digital work behaviors, not to audit a specific office setup.
- It includes both the device and the infrastructure supporting the session.
Uncertainty note: Work-tool emissions depend heavily on call quality, participant count, device efficiency, and how much multitasking happens during the session.
Yearly Impact Comparison
*IdleForest offsets ~200kg CO2/year on average per user.
Ways to reduce this footprint
- Turn video off when it is not necessary for the meeting outcome.
- Reduce meeting length and unnecessary participants when possible.
- Close heavy browser tabs and background tools during focused work.
Estimate review
Who reviewed this estimate
Reviewed by: IdleForest Research Team
Role: Editorial Review
Organization: IdleForest
Last reviewed: May 10, 2026
These estimates are meant to help compare digital habits. They are directional, not exact reproductions of proprietary vendor accounting.
Sources
Nature Communications: The environmental sustainability of digital content consumption
Peer-reviewed life-cycle assessment covering web use, social media, video, music streaming, and video conferencing.
IEA: Data centres and data transmission networks
Provides broader context on the infrastructure behind cloud and network energy use.
MIT CEEPR: How much can we reduce CO2 by planting trees?
Supports the offset conversion used by IdleForest: roughly 20kg CO2 absorbed per mature tree per year, with wide real-world variation.
More questions about Microsoft Outlook's carbon footprint
Why does Outlook have a footprint if email is lightweight?
The per-message footprint is small, but device time, attachment storage, search, notifications, and sync infrastructure create a measurable yearly total.
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