Why most gas meter guides get it wrong

Most "how to read your gas meter" guides tell you which digits to write down and stop there. That skips the part that actually matters: your meter does not record what you pay for. It records volume in cubic feet (ft³) or cubic metres (m³). Your bill is in kilowatt hours (kWh), and a multi-step calculation sits between the two: volume correction, regional calorific value, unit conversion. That calculation is where overcharging tends to hide.

5.74

Average gas unit rate

Ofgem cap, 1 Apr to 30 Jun 2026

×11.18

kWh from each m³

Volume correction × CV ÷ 3.6

71

Smart meter coverage

UK meters operating end-2025

How your gas meter actually works

A gas meter is a flow meter. The dials or digits on the front are a running total of volume that has passed through. You are billed for the chemical energy that volume releases when burned, not for the volume itself. The conversion uses three numbers:

  • 1.Volume correction (1.02264): adjusts for temperature and pressure against reference conditions.
  • 2.Calorific value (CV, typically 39.3 MJ/m³): energy your regional gas blend releases. Varies monthly.
  • 3.Divisor of 3.6: converts megajoules into kilowatt hours.

The formula for a metric (m³) meter is:

kWh = m³ × 1.02264 × CV ÷ 3.6

For an imperial (ft³) meter, multiply by 0.0283 first to convert into cubic metres.

Worked example: a metric meter

100 m³ used this month, CV at 39.3 MJ/m³:

  • 100 × 1.02264 × 39.3 ÷ 3.6 = 1 116 kWh;
  • 1 116 × 5.74p = £64.04 for unit charges.

Add the gas portion of the 57.21 p/day standing charge for 30 days and you have the full period bill.

Worked example: an imperial meter

Same household, 3 500 ft³ used in the month:

  • 3 500 × 0.0283 = 99.05 m³;
  • 99.05 × 1.02264 × 39.3 ÷ 3.6 = 1 106 kWh;
  • 1 106 × 5.74p = £63.48 for unit charges.

The imperial-to-kWh multiplier is roughly ×31.7, which is why a small ft³ reading turns into a much larger kWh figure on the bill.

The three types of UK gas meter and what each one means for your bill

Three meter families are still operating in UK homes. Each behaves differently at the meter and on the bill.

Imperial meter (cubic feet, ft³)

Standard in homes installed before 1995. Display reads in cubic feet, usually four black digits and two red ones. Record only the black digits.

How to identify: the display states "cubic feet" or "ft³". Older units have brass fittings and a black face.

Bill consequence: the ft³-to-kWh multiplier is roughly ×31.7, so a single mis-read digit translates into a much bigger error than on a metric meter.

Metric meter (cubic metres, m³)

Default for new and replacement installations since the mid-1990s. Display reads in cubic metres, usually five black digits and one red decimal. Record the five black digits.

How to identify: "cubic metres" or "m³" printed near the display, usually a digital LCD.

Bill consequence: the m³-to-kWh multiplier is about ×11.18, so the link between meter reading and bill is much easier to sanity check.

SMETS2 smart gas meter

Smart meter coverage reached 71% of UK meters by end-2025 (GOV.UK Smart Meters Statistics Report). The government target is 90% by end-2030. Most SMETS2 gas units record in m³ and submit readings automatically.

How to identify: small LCD, no dials, press a button to wake the display. A separate in-home display (IHD) shows usage in pounds and kWh.

Bill consequence: SMETS2 gas meters are battery powered and have no mobile connection. They pair by short-range radio to the electricity smart meter, which is the actual communications hub. If the electricity meter loses signal, gas readings stop flowing too, which is why some smart-meter households start receiving estimated bills again.

Advantages

  • Metric meters reduce conversion errors: one digit out is roughly 11.2 kWh, not ~31.7 kWh.
  • Metric meters are easier to cross-check against the kWh on your bill.
  • Smart meters remove human-reading mistakes entirely when they connect.

Disadvantages

  • Imperial meters use a large conversion factor that amplifies any reading mistake.
  • Imperial dials with sticky wheels can under or over-record without obvious signs.
  • SMETS2 gas readings stop if the paired electricity hub loses signal.

Where bill errors actually hide

If you suspect your gas bill is wrong, these are the three places to look first.

Imperial conversion mistakes

The most common error is an imperial reading being treated as if it were already in m³, or the wrong ft³-to-m³ factor being applied. With a downstream multiplier of roughly 31.7×, every small error shows up on the bill.

Sanity check: divide the kWh on your bill by your ft³ usage for the period. The result should land between 31 and 32. If it is closer to 11, your supplier is treating ft³ as m³ and you are being charged for nearly three times the energy you actually used.

Calorific value swings

UK gas is a blend, and the calorific value supplied to your region changes month to month. Typical CV is around 39.3 MJ/m³, but actual figures may sit anywhere from 38.5 to 41 by month and zone. Your bill must print the CV used; if it sits well outside that range, ask the supplier to confirm the source.

Stuck digits and U-error codes

Mechanical and dial meters can develop sticky digit wheels: readings sit frozen for weeks, then jump in a single day. SMETS2 gas meters surface their own faults as codes, notably U1 (gas valve closed) and U2 (low battery, common after about seven years). If you see a U code or a meter that has not moved despite normal use, contact your supplier the same week.

What you should actually do

Three practical steps from this guide.

  1. Identify your meter type. Look for "ft³" or "m³" near the display, or the smart meter LCD with no dials.
  2. Submit a reading on the same date each month. Imperial owners gain the most from this; smart meter owners should still confirm their in-home display is updating.
  3. Run the kWh-divided-by-volume check. On any recent bill, divide kWh by m³ or ft³ used. The ratio should be roughly 11.2 (metric) or 31.7 (imperial). Anything else is worth a phone call.

Your supplier must investigate a disputed reading and, if your meter is faulty and you have been overcharged, refund the period in full. The lab test cost sits with them unless the meter is confirmed accurate.

Once your meter and bill agree, the next saving usually lies in your tariff. Compare current deals on our cheapest gas suppliers page. If you suspect an error on the supply side, knowing your MPRN number speeds up every supplier call.

Convert your gas reading to a bill estimate

Pick your meter type, enter two readings, and we will run the full kWh conversion at the current cap rate. Useful for sanity-checking a bill.

Your meter

Meter type

Your estimated bill

Rates verified 2026-05-18. Source: Ofgem price cap 1 Apr to 30 Jun 2026. Gas standing charge taken as half of the 57.21 p/day dual-fuel average. Your bill may differ by region and tariff.

Frequently asked questions

', ], [ 'title' => 'Why does my SMETS2 gas meter stop sending readings sometimes?', 'content' => '

The gas meter is battery powered and has no mobile connection. It pairs by short-range radio to your electricity smart meter, which is the actual communications hub. If the electricity meter loses signal, gas readings also stop flowing.

', ], [ 'title' => 'What is the calorific value and why does it vary?', 'content' => '

The calorific value (CV) is the energy a cubic metre of gas releases when burned, in megajoules per m³. UK gas is a blend, so the CV varies by region and month. A typical figure is 39.3, with normal range 38 to 41.

', ], [ 'title' => 'My meter has not moved for weeks but I am using gas. What now?', 'content' => '

Contact your supplier the same week. They must investigate, send the meter for testing if needed, and fit a replacement. If the meter is faulty and you have been overcharged, they must refund the period in full.

', ], [ 'title' => 'Can I move my own gas meter to make access easier?', 'content' => '

No. Moving a gas meter without certification is illegal and dangerous. Contact your supplier, who can arrange a relocation for a fee. Priority Services Register customers may qualify for free or reduced-cost moves.

', ], ]" />