How we calculate a saving

1. We value savings at what the kit actually draws, not what it’s rated for

This is the arithmetic, and it is the most important thing on this page.

For every load we control, we hold its measured average consumption in the conditions it was running in. When one of our rules switches that load off, the saving we credit is:

the time it was off × the measured average for that load in those conditions

Never its rated power multiplied by hours. That distinction is the whole point. A heater or an air-conditioning unit cycles; its rated power is the draw at full call, and its actual average draw across a week is materially lower.

Conditions matter, so we compare like with like. The same heater behaves differently at a different outside temperature, and inside working hours or outside them (weekdays, 6am to 6pm, by the clock). We match on all three of those, the kind of circuit, the outside temperature and working hours, before we value anything, and the last one carries as much weight as the temperature does, because a 9 °C Monday morning behaves nothing like a 9 °C Sunday evening.

And that average is taken across every hour in the comparison, including the hours the load was drawing nothing. That is what accounts for the periods a thermostat would have switched it off anyway: those idle hours sit in the divisor, so they pull the average down and the saving down with it. Dividing by the drawing hours alone would credit us for hours the load would have been off regardless, which is the error this method exists to avoid.

This produces a substantially smaller number than the rated-power arithmetic would, and that is deliberate. It is the part of the method that reduces the figure we get to claim, and it does so on every load, every week.

The averages are not fixed, and that is part of this mechanism rather than a separate one. Monitored data from every site rolls up daily and refines them, so the record behind your numbers grows every week rather than sitting still. One site gives us a baseline; a programme gives us a benchmark we can stand behind.

2. We prove it week against week, on your own site, before you pay anything

We monitor until your consumption has settled, then take the seven days ending the day before the control goes on as your baseline. The control goes on, and the seven days beginning the day after is measured against it. The changeover day itself is excluded from both periods; the control is applied part-way through that day at no fixed time, so it belongs to neither. That is 14 of 15 consecutive days, and we state the gap rather than leave it unexplained.

So the difference is measured, not modelled. Equal seven-day periods mean weather, occupancy and trade mix are as close as they can practically be, which is why we use them rather than comparing across seasons. It is the closest control available and it needs no assumptions. Both periods are read straight off the same meter, with no scaling or normalisation applied; neither figure is modelled.

The full detail of that comparison, why equal weeks are the strongest test available, what we deliberately do not correct for, and what happens when a site works one week on and one week off, is on one week on, one week off.

The proof is your own site. The rate comes from everybody’s

These are two different things and it is worth being exact about which is which.

The two weeks that prove the control works are yours, your cabins, your meter, nothing pooled. That is mechanism 2 above, and it is the part that decides whether you pay us anything.

What an hour of switching-off is worth is drawn from everything we monitor, matched on those three conditions. Your figures are measured against the largest record of welfare-cabin energy behaviour in UK construction, and it grows every week.

That is deliberate, and it is the stronger way round. An average built from one site is a small number of hours and a shaky figure. Built from every site we monitor, it is the most reliable estimate of what that equipment really draws that anyone in this industry has. It is also why cabins not being interchangeable matters so much, a drying room and a site office have nothing in common electrically, so the record is only useful because every hour in it is matched on the kind of circuit, the outside temperature, and whether it was inside working hours.

And we can tell you how many measured hours sit behind any figure we give you. Where a particular combination is thin, we say so rather than let the number stand unqualified.