How to Read the World Electricity Clock

The big number on the World Electricity Clock is the electricity metered since 00:00 UTC today, summed across the grids whose operators publish fresh readings often enough to count. It rises because power keeps flowing, and it pauses when a source goes quiet, because we will not count electricity that no meter has reported.

This guide explains how that number is built, which markets are inside it, what the badges and the smaller counters mean, and why some figures, such as the U.S. totals and the carbon counter, are treated differently.

What the big number counts

Each market on the clock publishes a series of readings: a power level, in megawatts, for each reporting interval. To turn power into energy we join today’s readings with straight lines and measure the area underneath, a trapezoid integral. The last reading is counted over its own interval, because the sources stamp each value at the start of the interval it covers. If two readings are separated by more than two reporting intervals, the gap is left out and never filled in.

The result, per market, is a total in megawatt-hours since 00:00 UTC. We call it the anchor. The anchors are written into the page itself, and the big number is their sum. The list below the main counter, showing where the electricity is used, uses the same anchors, so its rows always add up to the main counter.

The day starts at midnight UTC for every market, not at local midnight. A market also starts counting only at its first reading of the UTC day, so on the first day a market is collected, its total covers only part of that day.

Which markets are in the cohort

Not every market on the site enters the total. A market is counted only if it reports every 30 minutes or faster, its data is current, and its readings cover at least 95 % of the UTC day so far. Until it reaches that coverage, the clock shows its current rate as “now” and lists it as a partial day. This rule stops a market with a long gap from distorting the total by appearing with half a day of energy.

Market	Source	What is counted	Reporting interval
Great Britain	Elexon BMRS, FUELINST	Transmission-connected generation; interconnector imports excluded, pumped storage net	5 minutes
Denmark	Energinet, Energi Data Service	Demand calculated from production and cross-border exchange (Derived)	5 minutes
Australia (NEM regions)	AEMO, NEMWEB	Dispatch total demand per region	5 minutes
Taiwan	Taipower via data.gov.tw	Current system load	About 10 minutes
United States	EIA-930 Hourly Electric Grid Monitor	Hourly demand by balancing authority, shown separately	Hourly, delayed

Two entries need a note. Great Britain is counted from generation, not consumption, because Elexon’s half-hourly demand series arrives about an hour late; interconnector imports are excluded because that power is generated abroad. Denmark publishes no near-real-time consumption field, so we calculate Danish demand from each five-minute row of production plus imports minus exports, and badge it Derived. The methodology gives the exact formula.

The line “Metered to” shows the latest time that more than half of the counted markets have reached. Markets still behind that time are named in the ⓘ panel.

Why it ticks, and when it pauses

Between two readings, the counter in your browser continues at the last metered rate: anchor plus rate multiplied by the time since the last reading. That is why the digits move smoothly rather than jumping every five minutes. The small digits after the point are kilowatt-hours of the same flow, and the “MWh every second” figure is simply the current metered rate divided by 3,600.

This continuation is bounded. A market keeps adding at its last rate for at most 15 minutes after its last reading. After that it stops, and the counter shows “paused · waiting for data” until a new reading arrives. We do not extrapolate trends, invent a rate or animate a number to make it look live.

Every minute the page fetches fresh anchors. When a new metered total is lower than the browser’s running count, the counter never runs backwards; it waits for the metered total to catch up. When the new total is higher, the counter moves forward to it over about three seconds. Over a day, the displayed number therefore stays tied to what the operators have actually published.

When no market yet has a full metered day, the “Since you opened this page” counter still runs on the latest fresh readings, under the same 15-minute limit.

Metered, Derived and Estimated

Every figure on the site carries one of three badges. They are not drawn next to every number, but each figure has one in the page code, and the ⓘ panels name it.

Metered means the value is the operator’s own published figure: a price, a demand reading or a generation level, taken as published.

Derived means we calculated it from metered values with simple arithmetic: a total, a sum over time, a renewable share or a currency conversion. The clock’s energy total is built this way from metered readings, and Danish demand is Derived because it is calculated from production and exchange.

Estimated is reserved for values modelled beyond simple arithmetic. On the clock, the carbon counter is marked Estimated.

Why the U.S. is shown separately

The U.S. figures come from the EIA Hourly Electric Grid Monitor, built on the EIA-930 survey of balancing authorities. They are hourly, preliminary and revised later, and they reach us an hour or two after the hour they describe. Mixing them into a counter that moves every second would either stall the total or force us to guess the missing hours. So the U.S. operators sit in their own block below the main counter, shown at their last published values, and that block does not tick.

The carbon counter is an estimate

The CO₂ counter multiplies metered generation by fuel by published lifecycle emission factors, the median values in Annex III of the IPCC’s Fifth Assessment Report, Working Group III. It is marked Estimated because a lifecycle factor is a general average, not a measurement of the plants running today. Oil has no median in that table, so a proxy is used. Denmark is left out because its thermal output is not split by fuel, and fuels in the “other” group are not counted. The carbon figure is therefore a partial estimate, not a measured carbon intensity for the grids shown.

Cheapest hours and forecasts

The clock itself makes no forecasts. The only forward-looking prices on the site appear on the Australian cheapest-hours pages, where hours still to come use AEMO’s published pre-dispatch prices and are labelled “forecast by AEMO”. Danish cheapest-hours tables show tomorrow only after the day-ahead auction result is published, and that is a cleared price, not a forecast. Everything else holds its last published value until a new reading arrives.

Where the data comes from

We publish only sources whose licence clearly allows commercial redistribution, and the required attribution appears on every page that uses them. Elexon’s BMRS data is used under its data licence with the copyright notice it requires. Energinet’s Energi Data Service is licensed under Creative Commons Attribution 4.0. AEMO material is used under AEMO’s general copyright permission with attribution. Taipower’s data comes through data.gov.tw under the Open Government Data License, Taiwan v1.0. EIA publications are in the public domain as U.S. government works.

Other grid operators are collected for research only and are not shown. All figures are provisional, operators revise their data, and nothing on the clock is suitable for trading or operational decisions.