Advanced options
What The Shower Cost Calculator Works Out
- Cost per shower: energy plus water. An electric shower draws its rated 9kW for the minutes it runs, so eight minutes is 1.2 kWh of peak-rate electricity (about 32p at the current price cap) plus about 40 litres of water at 5 litres a minute, roughly 50p all-in on a metered supply. A gas mixer heats the litres drawn (0.035 kWh per litre, through an 85% efficient boiler) at a quarter of the price per kWh but pushes 10 litres a minute; a 14-litre-a-minute power shower quietly out-spends both.
- Per year (household): the per-shower cost x showers per day x 365. A family showering daily each runs into hundreds of pounds a year, which is why the shower sits near the top of every water company's and energy adviser's target list.
- Two minutes shorter would save: nearly all the cost is heating water, so fewer minutes and fewer litres per minute are the only levers that matter. A 4-minute timer is the classic water-company freebie.
- Unit rates and boiler efficiency (advanced): edit the electricity and gas prices (both default to the current Ofgem price cap unit rates) and the boiler's efficiency. On Economy 7 the electric shower's peak-rate habit is the expensive exception to otherwise cheap nights.
- Water supply and rate (advanced): switch to unmetered to drop the water line, or enter your company's combined supply-and-sewerage rate. Metering turns every litre into money and roughly half of it into sewerage charges.
- Flow rate and shower power (advanced): override the default flow with a measured figure (time a 10 litre bucket) and set the electric shower's kW rating. 9kW can only heat so much water so fast, which is why electric showers run weak in winter when mains water arrives colder.
- Cost per minute and per month (advanced): the per-shower cost divided by its length, and the household monthly total, for comparing with other bills.
- Water-saving head (advanced): the annual saving from a regulated or aerated head at around 8 litres a minute on mixers and power showers, where the felt difference is small. Electric showers are already low-flow by design, so only the water share changes.
- Versus a bath (advanced): a typical bath holds about 80 litres of hot water, so a shower beats it unless it lingers past ten minutes or so under a high-flow head. Hot water is commonly a household's second energy cost after space heating.