As readers know, I am fond of dissecting the components of a domestic electricity bill, or at least, I intermittently drag myself into doing it out of a sense of duty. I set out to do a six-monthly update of this on Friday evening [11^th September], but was immediately distracted by something else in the data. The butterfly that caught my eye was:

Typical Domestic Consumption Value

[Skip the numbery part below, if you like. I would, if I could.]

The TDCV is the amount of electricity and gas used by the “typical” household, and is used by Ofgem to set the value of the default tariff cap. It has recently been reduced, as follows:

Period	Gas TDCV	Electricity TDCV
Prior to October 2023	12 KWh	2.9 KWh
October 2023 to June 2026	11.5 KWh	2.7 KWh
July 2026 onwards	9.5 KWh	2.5 KWh

However, you’ll be pleased to know that things aren’t quite that simple. Ofgem’s latest (1.11) Annex 9 sheet gives calculations based on different figures and dates for benchmark use. Note that benchmark use has been different to the TDCV. However, from July 2026, the two have been aligned. These are the dates and benchmarks used in that spreadsheet to (currently) calculate (historical) price caps:

Period	Gas benchmark use	Electricity benchmark use
April 2018 to December 2025	12 KWh	3.1 KWh
January 2026 to June 2026	11.5 KWh	2.7 KWh
July 2026 onwards	9.5 KWh	2.5 KWh

It means that, although I once earnestly reported that the price cap from January to March 2025, as reported by Ofgem, was £1738, that figure can no longer be found in the present spreadsheets (that I can see). Instead, you can have £1561 or £1869 (or £1862 on a different spreadsheet) for those dates. Ignoring the parenthetical value, the first is based on the present TDCV (i.e. calculated using the present benchmark = TDCV usage), and the second is based on the benchmark use shown in the table above (i.e. it is as calculated “at the time,” although clearly not as the numbers don’t match to the present spreadsheet). Don’t worry if you’re not confused yet. Or don’t be confused if you’re not worried yet. Or something.

The effect of reducing the TDCV (or benchmark, if that differs) over time

Naturally, when you calculate the energy price cap, if you reduce the benchmark amount of energy people are using, the value of the price cap comes down. Nothing nefarious has gone on here, although when Ofgem says the spreadsheets are “not fully accessible,” several choice rejoinders spring to mind. The important point is that households are using less energy than they were. A supplementary point is that old default tariffs, price caps, are no longer easily comparable to the current one, and that it would be easy for a slippery politician to claim a reduction in cost, when what has really gone on is a reduction in use. (I’m not saying this has happened. I haven’t looked.)

The two figures on Ofgem’s main sheet represent i) what the old price cap would have been, if it had been calculated using today’s TDCV – no difficulty in understanding this (e.g., £1561), and ii) old price caps that might have been, and probably never were, based on benchmarks that didn’t match the TDCV when the calculation was made (e.g., £1869). These two figures are shown in Ofgem’s current sheet, when the “announced” figure at the time was £1738. The first is the “fair comparison.” The other goes down in recent quarters, based on the reduced benchmark use in the second table above. Beginning at the period April to June 2024, when M. Miliband made his “promise” to cut bills by £300, the next table shows how different versions of the price caps have evolved. Three values are shown: as reported today, had the present TDCV / benchmark been in position back then; as reported today for the historical benchmark; and as announced in the contemporary Ofgem letter.

Period	Price cap, £, as it would have been if today’s TDCV / benchmark was in place	As it would have been under then-existing benchmark	As announced in the letter
April 2024 – June 2024	1520	1818	1690
July 2024 – September 2024	1414	1685	1568
Oct 2024 – Dec 2024	1543	1846	1717
Jan 2025 – Mar 2025	1561	1869	1738
Apr 2025 – June 2025	1655	1992	1849
Jul 2025 – Sept 2025	1541	1854	1720
Oct 2025 – Dec 2025	1576	1891	1755
Jan 2026 – Mar 2026	1584	1758	1758
Apr 2026 – June 2026	1477	1641	1641
Jul 2026 – Sept 2026	1663	1663	1663
Oct 2026 – Dec 2026	1723	1723	1723

So, only the two most recent price caps are the same on all measures, after Ofgem decided to use the TDCV to set the benchmark use. From January to June 2026, “as announced” matches “as it would have been under then-existing benchmark,” and before that, nothing matches (the benchmarks used for electricity seem to be 2500 KWh, 3100 KWh and 2700 KWh, reading across left to right) (ish).

At a constant present TDCV, the price cap has gone up £203 since the advent of Milibandism. Under “then-current benchmark,” it has gone down £95, and under “as announced,” it has gone up £33. The most recent price cap includes a temporary removal of VAT on electricity, and the movement of some components off bills and onto general taxation.

[Unreadable number-crunching ends. Begin reading now, if you like.]

Why has TDCV fallen?

On the face of it, gas usage in the typical household has gone down 20% over three years, and electricity has gone down 14-20% depending on which benchmark you use. There are a range of potential explanations for this, and I’m sure that some would love it if the decrease could be laid at the door of improved insulation. Helpfully the original Ofgem TDCV consultation document of March 2026 discusses the consumption drivers. Their estimate of the change in energy use goes back 20 years:

This [the present decrease in use] is the continuation of a trend that in total since 2005 has seen total domestic electricity consumption fall by about 18% and gas by about 32%.

The potential drivers are:

1. Long-term energy efficiency increases
2. Warmer seasonal temperatures
3. Micro-generation (rooftop solar, etc)
4. Reduced use in response to increased cost

Ofgem are not willing to tiptoe around the tulips, so well done to them:

While factors such as energy efficiency improvements and climatic trends may continue to influence the longer term reduction in consumption, the scale and persistence of the recent decline in consumption is most consistent with a change in consumption behaviour.

…

Throughout the wholesale price crisis, consumers significantly reduced demand in response to affordability pressures, due to both high energy bills and wider cost of living pressures.

The reduction in use may have been stimulated by the astronomical price hikes of a few years ago, but it has not gone away since (probably because the price may have settled, but it has not returned to pre-2022 levels).

It seems to me that you can measure wealth in terms of energy use as well as actual cash. Remembering Jevons’ Paradox, an increase in efficiency alone might be expected to result in increased energy use. Instead, we citizens of the UK are not doing things we would otherwise have done, and are therefore poorer. That is the bitter fruit of Net Zero. Remember, They do not want you to use more energy. Therefore, should there be efficiency gains, They will impose greater costs, in order to deter use, to sidestep Jevons, and “save the planet.”

/tinfoil hattery

Old episodes in this series:

Energy price cap watch (December 2024)

Nervous breakdown of an electricity bill (April 2025)

Breakdown of a leccy bill 2026 (March 2026)

All Ofgem’s Energy Price Caps are available here.