Charge fantôme: Ce que coûtent vos appareils électroniques de bureau pendant votre sommeil

À 19:00 the office empties. The lights go off, and the meter keeps ticking — because fifty desks worth of electronics never actually switched off. They are waiting: for a remote signal, a print job, a wake-on-LAN packet, or the next « good morning. »

That waiting has a name — phantom load — and a long measurement record. Here is what the labs found, what it costs a 50-person office in euros, and what a €25 strip does about it.

Ce que les laboratoires ont réellement mesuré

These are metered figures, not poster estimates.

Lawrence Berkeley National Laboratory (LBNL) has run standby research since the 1990s. In the first whole-home metering study (Ross & Meier), the average house carried 67 W of standby load across 19 devices — between 5% et 26% of its annual electricity, with printers among the worst offenders. Berkeley Lab’s standing rule of thumb: one watt left on around the clock burns about 9 kWh per year. Its FAQ puts standby at 5–10% of electricity use in developed countries, and notes commercial buildings are « smaller but still significant. »

The IEA’s 4E programme compiled 19,000 shop-floor measurements across ten product categories. By 2011, most standby draws sat under 3 W — but networked devices were the exception, with some boxes averaging 25 Quelles imprimantes sont les moins chères à utiliser. A 2017 UK verification round measured five printers at 0.1–0.3 W: modern printers are cheap sleepers; the old ones and the all-in-ones are not.

L’UE’s REMODECE project, which metered 1,300 homes across Europe, measured an average standby load of about 40 W — 305 kWh per household per year, roughly 11% of household electricity. For offices, the project’s companion estimate put standby on office equipment across the EU-27 at 9.43 TWh per year — at H1 2026 average business prices, close to €1.7 billion a year.

ADEME, the French environment agency, counts 15 à 50 devices in standby in a typical home at 0.5–3 W each, and its appliance tables price an older espresso machine’s keep-warm at around 100 kWh a year. Which?‘s lab testing puts always-listening smart speakers at up to £6 per device per year in standby — the office equivalent of the conference-room speakerphone that never sleeps. US DOE rounds the phenomenon to 5–10% of building electricity use.

The 50-person office, line by line

Take a standard office: 50 desks with a monitor and a desktop, four shared printers, two coffee machines, a water cooler, 60 chargers and docks in drawers, and one snack vending machine. Every watt below is at or under the measured medians above.

Charge	Standby draw	kWh/an	Cost/year
50 monitors	50 Quelles imprimantes sont les moins chères à utiliser (1 W each)	438	€79
50 desktop PCs	100 Quelles imprimantes sont les moins chères à utiliser (2 W each)	876	€158
4 printers/MFDs	12 Quelles imprimantes sont les moins chères à utiliser (3 W each)	105	€19
2 coffee machines	10 Quelles imprimantes sont les moins chères à utiliser (5 W each)	88	€16
Water cooler	3 Quelles imprimantes sont les moins chères à utiliser	26	€5
60 chargers/docks	18 Quelles imprimantes sont les moins chères à utiliser (0.3 W each)	158	€28
Speakers/webcams/misc	25 Quelles imprimantes sont les moins chères à utiliser (0.5 W each)	219	€39
Vending machine	~69 W average	600	€108
Total	~287 W	~2,510	~€452

Pricing at €0.18/kWh — Eurostat’s EU average for businesses using 500–2,000 MWh/year, excluding VAT, for January–June 2026 — the sleeping office costs about €452 a year, roughly €9 per desk. In Dublin or Milan, where the same Eurostat table shows €0.25–0.27/kWh, it is closer to €650.

Sanity check before anyone books a retrofit: €452 is real but modest, and it should be. Berkeley Lab’s own researchers warn the office share is smaller than the residential 5–10%, because office gear is newer and power-managed. Honest framing: phantom load is 1–2% of a typical office electricity bill, not a crisis — a rounding error you can delete for free. The vending machine alone is a quarter of it.

Ce que tu sauves

~€452 per year for a 50-person office at the EU average business price (€0.18/kWh) — about €9 per desk. Kill-switching the recoverable loads (everything except the network and the vending machine’s compressor) at a realistic 70% capture returns ~€315 a year. Add the CO₂ the same way: at the EU average grid factor (~310 g/kWh), that is ~0.8 tonnes a year — one economy flight a year, from a habit change.

Les mathématiques du coup d’interrupteur

A 50-person office needs roughly 15 switched or smart strips: one per desk cluster, one per printer, one per kitchen counter. At €25 each with real relays, that is a €375 kit, installed in an afternoon by whoever owns the extension leads.

• Full capture (everything switched every night): €452/year → payback in 10 months.
• Realistic capture (70% — someone forgets, some boxes must stay up): €316/year → payback in about 14 months, then €316/year free forever after.
• A building-level controllable circuit with contactors pays back in the same window only if the electrician’s quote stays under €3,000. For one floor, strips win.

Two rules keep the math honest. Don’t kill what must live: Wi-Fi access points, the alarm, the server, the PBX. And don’t kill the vending machine’s compressor at night — letting refrigeration re-pull temperature can cost more than it saves. Kill its lighting, not its cooling.

Qu’est-ce qu’il ne faut pas s’embêter

A single phone charger left plugged in draws about 0.3 W — €0.48 a year. Chasing individual chargers is theatre. The desk cluster (Moniteur + PC + dock + speaker) holds 60% of the euros, the vending machine a quarter. Measure one desk cluster with a €20 plug-in watt meter at 21:00 before spending anything: if it reads under 5 Quelles imprimantes sont les moins chères à utiliser, your power management already works and you can skip this whole article.

Sources

• LBNL, Standby Power FAQ (5–10% share, 9 kWh per watt-year, commercial note): https://standby.lbl.gov/frequently-asked-questions
• Ross & Meier, Whole-House Measurements of Standby Power, LBNL-45967 (67 Moyenne W, 5–26%, printers top offenders): https://eta-publications.lbl.gov/sites/default/files/lbnl-45967.pdf
• LBNL, Homes that « Leak » Électricité (50 Moyenne W, ~5%): https://www2.lbl.gov/Science-Articles/Archive/leaking-watts.html
• IEA-4E DESAM policy brief, 19,000 standby measurements (sub-3 W medians, 25 W boxes): https://iea-4e.org/wp-content/uploads/publications/2013/03/4E_Policy_Brief_MB10.pdf
• IEA-4E, Standby consumption report UK 2017 (printers at 0.1–0.3 W): https://iea-4e.org/wp-content/uploads/publications/2017/04/Standby_consumption_report_-_UK_version_FINAL.pdf
• REMODECE / SELINA, EU standby monitoring (40 W and 305 kWh per household; 9.43 TWh EU-27 office standby): https://www.researchgate.net/publication/270576891_Standby_and_off-mode_Power_Demand_of_new_Appliances_in_the_Market and https://remodece.isr.uc.pt
• ADEME, appareils les plus énergivores (device tables, digital = 11% of French electricity): https://agirpourlatransition.ademe.fr/particuliers/economiser/energie/consommation-appareils-menagers
• Which?, appliance running-cost lab data (smart speaker standby): https://www.which.co.uk/reviews/cutting-your-energy-bills/article/how-much-your-appliances-cost-to-run-a7N937v2SWom
• US DOE, Shut Down and Unplug (5–10% of building electricity): https://www.energy.gov/articles/save-energy-shut-down-and-unplug-your-electronic-devices
• Eurostat, business electricity prices H1 2026 (EU average €0.18/kWh, band 500–2,000 MWh, excl. TVA): https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Electricity_price_statistics

Prochaine fuite à réparer

The desk cluster is tonight’s job. Tomorrow’s is the machines that never sleep — right-sizing the fleet itself: Technologies de l’information verte & Devices →

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Carla Lavigne is Green Ops Editor at mycompanyisgreen.org and the colleague who brings the calculator to the audit.