Tue 1 Sep 2026 · Elexon & NESO half-hourly data
Energy prices are about to move by the hour.
Your building still runs on a timer.
Business energy contracts run for years. Sign a new one this year and your next renewal is likely to be a time-of-day tariff. The buildings that handle that renewal well are the ones that spend the years in between learning how they actually use energy.
You already experience this at home with your washing machine.
If anybody has ever told you to put the washing on late because it is cheaper, you already understand the idea. Electricity costs different amounts depending on where it comes from: gas, solar, wind or nuclear. On top of that, the grid carrying it gets busy or quiet through the day. When demand is high, it costs more. When the grid is quiet, it costs less. That is why the price changes from hour to hour. Until now, your commercial building never had to worry about it. The hourly price is about to become transparent for commercial buildings.
Hover or tap any half hour · Tuesday 1 September 2026
Great Britain, Tuesday 1 September 2026. Wholesale price: Elexon Market Index Data, shown in pence a unit. Carbon: NESO Carbon Intensity API. Both are published half-hourly actuals, not forecasts. Wholesale is only one part of what a supplier pays. A business’s bill also depends on network costs, levies and the terms of its contract.
Six times the wholesale price and nearly three times the carbon, for the same unit of electricity, six hours apart on an ordinary Tuesday. Your tariff may smooth that out today. Your supplier still sees it, and a dynamic or time-of-day contract can pass more of it on to you. Your building cannot respond, because nothing connects the price to its schedule.
More detail: the day in two charts, the past month and three terms explained
Low 3.2p a unit at 13:30. High 19.1p a unit at 19:30. Six times over, same day.
Low 54 g at 10:00 and 13:00. High 164 g at 22:30 and 23:00. Three times over, same day.
Great Britain, Tuesday 1 September 2026. Prices: Elexon market index data, shown in pence a unit. Carbon: NESO Carbon Intensity API. Both are published half-hourly actuals, not forecasts.
Look at the two charts. They share part of the same daily pattern, but price and carbon are not the same thing. On this day, carbon in the cheapest half hour was within two grams of the day’s lowest, and carbon in the dearest half hour was within five grams of the day’s highest. On other days the two drift apart, because grid bottlenecks, demand, imports and the mix of power sources affect price and carbon differently.
Ranges verified across 1,488 half-hour periods from 3 August to 2 September 2026. The carbon range leaves out one isolated reading of 0 g a unit on 6 August, treated as a data-quality outlier; the next-lowest reading was 34 g.
Settlement matches what your site used in each half hour to the cost your supplier faces for serving it. It does not automatically put you on a dynamic tariff, but it makes your pattern of use visible and gives suppliers a reason to offer prices that reward flexibility.
Changing when you use energy, rather than using less of it. Nobody is asking the building to be colder or darker, only to do some of the same things half an hour earlier or later.
A unit on a bill is one kWh. Wholesale prices are quoted per MWh, which is a thousand units, so £191 per MWh is 19.1p a unit. This page shows every price in pence a unit, and grid carbon in grams of CO₂ a unit.
Britain now makes more clean power than the grid can carry.
So we pay generators to change output when electricity is in the wrong place at the wrong time. NESO, which runs Britain’s electricity system, says thermal constraint costs, paid when the wires cannot carry the power, reached £1.82 billion in 2025, up 23 per cent on 2024. In August 2026 it forecast £3.2 billion of constraint costs over the following twelve months. There are two broad ways out: build more grid capacity, or move some demand to the times when the power is already there.
London is already living with this. Parts of the west London network have been effectively full since 2022, when the Greater London Authority warned that developments in Ealing, Hillingdon and Hounslow faced years of waiting for a grid connection. The queues and local limits reach well beyond London, and that is why time-of-day tariffs are coming: the buildings that can move some of their demand are the ones that will be asked to move it.
Moving demand is the faster of the two. Price is one way to ask millions of buildings to change when they use power, but it only works if a building can act on it. Nobody is telling your building when to run. The price advises it to run at cheaper, greener times, so the country uses more clean power while it is available and buys less gas from elsewhere. That improves UK energy security, and your building helps deliver it.
When does your contract end?
What catches people out has nothing to do with technology. It is a diary problem. Ofgem says business energy contracts can run for up to five years. A contract signed now could still be running when the move to market-wide half-hourly settlement is due to finish in May 2027, and when the new settlement timetable starts in July 2027.
We recently watched a landmark London venue go through a renewal conversation. They were about to sign a deal that would still be running after the 2027 changes, which makes their next renewal likely to be a time-of-day tariff. Nobody in the room mentioned it, or that the years in between are the time to get the building ready.
Forget new builds. This is about the building you run today.
An ordinary commercial building on an ordinary estate, with an energy contract that renews on a date already in somebody’s diary. The risk is that the date arrives before you know how the building uses energy through the day, and you are locked into the next contract without that knowledge.
The programme dates are set. Your tariff is a choice.
Settlement is how a supplier’s costs are matched to what its customers used. Larger commercial sites have been settled on what they actually use in each half hour since April 2017. Market-wide half-hourly settlement extends the same approach to the rest of the market. It changes how suppliers are settled; it does not force every customer onto a dynamic tariff. The pressure on you comes through the tariffs, passed-on costs and renewal prices that suppliers choose to offer.
A third of Britain’s meters have switched.
By the middle of June 2026, more than 11.3 million meters had moved to half-hourly settlement. Once a site is settled half-hourly, the way it uses energy through the day becomes visible to whoever prices its electricity.
DESNZ, Ofgem and NESO Clean Flexibility Roadmap, July 2026 updateThe systems behind time-of-day tariffs arrive.
Industry codes and suppliers’ licence conditions have been changed so that suppliers share time-of-day tariff data in a standard way. The first phase is due in February 2027, making flexible tariffs easier to offer and compare across the market.
DESNZ, Ofgem and NESO Clean Flexibility Roadmap, July 2026 updateThe switchover finishes.
All suppliers are due to move every meter point onto half-hourly settlement by 7 May 2027. On 2 July 2027 the market switches to the new four-month settlement timetable. On 2 September 2026 the programme confirmed that its next milestone for supplier readiness is still on track.
Market-wide Half-Hourly Settlement programme milestones, updated 2 September 2026Somebody has to supply the flexibility.
NESO, the electricity system operator, is looking for an extra 750 MW of flexibility from commercial and industrial sites by 2030, and met its first-year target early. Meanwhile, the government is redesigning the frameworks that schools, hospitals and government buildings use to buy energy, so that they include flexible supply. If you sell into public estates, this arrives in your tenders before it arrives in your bills.
NESO non-domestic flexibility target · Government Commercial Agency commitmentThese changes are not a question of if, but when. Are you prepared? Is yours a Future Ready Building?
The market can make 48 price decisions a day. Your building cannot.
Your building management system (BMS) is good at what it was built for. It holds the building at temperature, runs the heating and cooling plant and follows the times it was given. But a fixed schedule cannot see that tomorrow’s prices have changed and decide to pre-heat at 05:30, ease off at 17:00 or warm back up at 20:30.
What your BMS does not have is any idea what the next twenty-four hours will cost, what the wind is doing or what the grid is running on right now. Buy a brand new one tomorrow and that is still true. It is a very good pair of hands with no view out of the window.
And a dashboard does not fix it either. Plenty of software will show you the spike after it has happened, in a nice chart, and hand the problem straight back to you. A report you cannot act on is a chocolate teapot: exactly the right shape, and no use at all.
None of this is the facilities team’s failing. No person can review 48 prices, the weather, occupancy, plant limits and comfort every day, then keep rewriting schedules safely. The response has to be automatic, stay within safe limits and be easy to undo.
We do not replace your BMS. We sit above it and give it better times to run, using the building’s ability to hold heat and tomorrow’s weather forecast.
Two buildings. Same energy. Very different bill.
Two buildings on the same street, the same size, using the same total units of electricity across the year. On the same fixed unit rate they may still pay the same energy charge today. On a time-of-day or dynamic tariff, or when a supplier prices their next contract on when they use energy, they can pay very different amounts.
Leans into the cheap, clean hours.
On a day like 1 September, it does its heavy running around lunchtime, when wind and sun make power cheap and clean, then coasts through the evening peak on the warmth or coolness its structure already holds. Comfort never moves, so the people inside notice nothing.
On a time-of-day tariffBuys most of its energy in the cheaper, cleaner hoursRuns whenever it always has.
Keeps its heating and cooling running through the most expensive half hours of the evening, every day, because that is what the schedule says and nothing in the building knows any different. Nobody is at fault. Nobody was ever given the information.
On the same tariffPays peak prices, every single dayHalf-hourly settlement makes two separate questions commercially visible: how much electricity did you use, and when did you use it? A fixed tariff may average out the difference for now, but suppliers can still put a price on when you use energy. High consumption is only part of the risk. The bigger risk is a building that cannot move any of its running to cheaper times when prices change.
The plant on the roof is not the problem.
Almost none of this is a kit question. The chillers, boilers and controls that will see you through the price change are the ones you already have. What has to change is when they run, and that is a schedule rather than a capital project.
You need to be Future Ready now.
No supplier can sell you a flexible building the week your tariff changes. A building only becomes flexible once somebody knows its pattern, and a pattern takes a run of seasons to be worth trusting. Future Ready Buildings start early, because that learning only begins once the building is connected.
Add it up and the work should start about eighteen months before your renewal: a year to learn the building’s pattern, then time to act on it before you sign. That is what we mean by Ready by Renewal, and for most estates it means starting now.
Getting ready pays for itself long before any of this lands.
The same work that makes a building flexible also takes the waste out of it, and that waste is costing you today. Plant running overnight in an empty building costs money whatever the tariff does.
across the estate
to report, from day one
with Visualise
you already own
So you cut the bill now, comfort untouched, and become a Future Ready Building as a side effect.
Three steps. Total clarity.
One journey rather than three products to choose between. You can stop at any point and still be better off than you were. It starts free, and comfort never suffers.
See what your building is really doing
Half hour by half hour, including the hours when the building is empty. Most estates find something running all night that had gone unnoticed. Switching it off saves money straight away, and connecting starts the clock on the data you will need.
Free to startCut the waste, keep the comfort
Using the building’s ability to hold heat and tomorrow’s weather forecast, we adjust when things run so they land in the cheaper, cleaner hours. This is where the 15 to 49 per cent comes from, and the people inside feel no difference.
The engineThe building answers the price
Now the building works with the grid in both directions, makes the most of wind and any solar panels of its own, and adapts as price and carbon change through the day. This is what all the earlier work was quietly making possible.
The destinationFind out how ready your building already is.
Start with Visualise. We take the half-hourly readings your building has already recorded and show you its pattern against what the grid was really doing. Within a month, you will know what it would take to be ready. No capital, no rip-out, no loss of comfort.
See your building. Free →