At a glance
The short answer: measure the gas used, not just the minutes
A shower supplied by a gas combi boiler or hot-water cylinder does not have one fixed cost. The boiler has to raise cold mains water to the temperature you use, so the result changes with the shower flow, shower length, incoming water temperature, boiler and pipe losses, and the gas unit rate on your tariff.
The most useful home check is to record the gas meter immediately before and after a normal shower while no other gas appliance is running. Convert the difference to kilowatt hours (kWh), then multiply it by the gas unit rate. In the worked example below, a measured 0.15 cubic metres (m³) is about 1.68 kWh and costs about 13p at 7.97p per kWh.
That 13p is an illustration, not a national average. Your shower could use less or more. A bath, power shower, long high-flow shower or stored-hot-water system will not necessarily match it, and an electric shower uses electricity rather than gas.
What changes the cost of a gas-heated shower?
Shower time is only one part of the calculation. Ofwat says a five-minute shower uses about 40 litres of water, but actual fittings vary. A higher flow sends more water through the boiler each minute, and colder incoming water needs a greater temperature rise. That is why the same eight-minute shower can cost differently in two homes or in summer and winter.
Boiler operation matters too. A combi boiler heats water on demand, while a system or regular boiler may heat a stored cylinder before the shower. Stored systems can lose heat between heating and use, so a meter test covering only the shower may miss gas burned earlier to reheat the cylinder. For those systems, compare similar full days rather than pretending one shower can be isolated precisely.
The standing charge does not become larger when you take a shower. It is a daily account charge that applies whether or not the shower runs, so include only the unit-rate cost when comparing one shower with another. Use the standing charge when estimating the whole bill.
- Duration: more minutes normally mean more hot water.
- Flow: litres per minute can matter as much as the timer.
- Temperature rise: hotter shower water and colder mains water require more energy.
- System: combi and stored-hot-water systems have different losses and timing.
- Tariff: use the gas price on your own bill, including VAT if shown that way.
How to measure one shower with your gas meter
Choose a time when the central heating is off and nobody needs another gas appliance. Record the meter reading, take a normal shower, then record it again once the boiler has stopped firing. Do not turn off the gas supply, remove a meter cover or change boiler internals. If your meter is inaccessible or you cannot safely identify the reading, use bill data over a longer period instead.
On a metric meter, subtract the first m³ reading from the second. Enter both readings in the gas bill calculator, or use the official bill formula: gas volume × calorific value × volume-correction factor ÷ 3.6. Your supplier uses the calorific value shown on the bill. The shortcut of roughly 11.2 kWh per m³ is useful for a quick check, but it is not the exact billed conversion.
Repeat the test on two or three comparable days if you want a steadier figure. A single result can include the boiler warming its heat exchanger or pipework, and a smart meter display may round or update later than the physical meter. Our gas units to kWh guide explains metric and imperial readings in detail.
- Before: make sure heating and other gas appliances are not running.
- Record: photograph or write down the full meter reading safely.
- Shower: use the normal duration, flow and temperature.
- After: wait for the boiler burner to stop, then take the second reading.
- Calculate: convert the difference to kWh and multiply by your unit rate.
Worked example: a measured 0.15 m³ shower
Suppose a metric gas meter rises by 0.15 m³ during the test. Using a calorific value of 39.5 megajoules per cubic metre and the standard 1.02264 correction factor, the billed-energy calculation is: 0.15 × 39.5 × 1.02264 ÷ 3.6 = 1.68 kWh.
At Ofgem’s Great Britain average Direct Debit gas rate of 7.97p per kWh for 1 October to 31 December 2026, the unit-rate cost is 1.68 × 7.97p = 13.4p, rounded to about 13p. Thirty identical showers would use about 50.5 kWh and cost about £4.02. This excludes the standing charge because the household pays that daily amount regardless of this shower.
Use the rates and calorific value on your own bill. Ofgem’s figure is an average for capped default tariffs in England, Scotland and Wales; rates vary by region, payment method and tariff, and Northern Ireland has a separate regulated energy market.
| Step | Calculation | Result |
|---|---|---|
| Measured gas volume | Second reading − first reading | 0.15 m³ |
| Convert to energy | 0.15 × 39.5 × 1.02264 ÷ 3.6 | 1.68 kWh |
| Apply unit rate | 1.68 × 7.97p | 13.4p |
| Thirty equal showers | 1.68 × 30 × 7.97p | £4.02 |
Illustrative meter result and October–December 2026 average GB Direct Debit rate. It is not a typical-shower claim or a tariff quote.
Measure flow as well as time
A bucket-and-timer check explains why the gas result changes. Run the shower into a marked container for ten seconds, measure the litres collected, then multiply by six to estimate litres per minute. For example, 1.3 litres in ten seconds is about 7.8 litres per minute. Do this only if the container is easy to handle and the shower floor remains safe.
Do not multiply litres by the gas unit rate. Water volume is not billed gas energy. Use it to compare the shower before and after changing the flow, while the meter supplies the actual gas-use figure. DESNZ research based on connected combi boilers found that hot-water demand varies by event, temperature, time and household, reinforcing why a measured result is more useful than a universal cost.
An electric shower is different: it heats cold water with electricity at the shower unit. Its cost should be calculated from electrical power and time, not from the gas meter. A mixer shower can draw from a gas-heated cylinder or combi boiler, so identify the heat source before comparing costs.
Reduce shower cost without unsafe boiler changes
Start with changes you can measure: shorten the shower slightly, avoid leaving it running before you step in, and consider a suitable water-efficient shower head. Energy Saving Trust recommends reducing hot-water use and checking whether a water-efficient shower head suits the system. Some heads are unsuitable for certain electric or low-pressure showers, so follow the product and boiler instructions.
Keep comfort and hygiene in view. Do not lower a stored hot-water cylinder thermostat based on a shower-cost article; cylinder temperature has separate safety considerations. Do not remove boiler covers or alter gas components. If water temperature surges, the boiler repeatedly cuts out, or performance has changed suddenly, use a Gas Safe registered engineer.
For broader savings, compare the shower test with the gas boiler running-cost guide and the central heating controls guide. If the bill still looks out of proportion to measured use, follow the checks in Why Is My Gas Bill So High? rather than assuming showers are the cause.
Frequently asked questions
Does a gas shower use gas or electricity?
A mixer shower supplied by a gas combi boiler or gas-heated cylinder uses gas to heat the water, though pumps and controls may also use a little electricity. An electric shower heats water in the shower unit and should be costed using electricity.
How much does a ten-minute gas shower cost?
There is no reliable fixed price from time alone. Flow, temperature rise, boiler performance and tariff all matter. Read the gas meter before and after a normal shower, convert the difference to kWh and multiply by your unit rate.
Should I include the gas standing charge?
Not when comparing the marginal cost of one shower. The standing charge is paid for each day the account is active whether or not the shower runs. Include it only in a whole-bill estimate.
Is a shower always cheaper than a bath?
Not always. Ofwat says a five-minute shower uses about 40 litres, around half a standard bath, but a long or high-flow shower can use as much water as a bath. Measure duration and flow rather than relying on the label.
Can I test a shower using a smart-meter display?
The display can show a trend, but it may round or update with a delay. Use the physical gas-meter readings for a more dependable before-and-after calculation, and repeat the test if the change is small.
Sources
Rates and rules checked on 8 November 2026. Time-sensitive figures should be checked again before use.