The tap, the television and you

Small everyday decisions, ranked by impact and without blame. Theory, formulas, worked examples and applications.

Five minutes of running tap is not just water

An open tap drags an entire chain behind it

The water flowing from a tap while someone washes dishes did not appear out of nowhere: it was captured from a river, a reservoir or an aquifer, transported, chemically treated until it was made drinkable, and pumped — often overcoming considerable elevation gains — until it reached that specific home. If the water comes out hot, its temperature also had to be deliberately raised, an energy expense that in most homes on its own exceeds that of the rest of the water cycle combined. After being used, that same water still has to be transported again and treated before it can be returned to the natural environment. Every one of these links consumes real energy, even though the person in front of the tap only sees water falling.

A screen left on with no one watching it provides no service at all

A television, a computer or a games console left on in an empty room keeps transforming electricity into light, sound and heat, exactly as if someone were enjoying that content — the difference is that this heat, light and sound no longer have anyone to benefit from them. The exact consumption of any specific screen depends on its size, panel technology, configured brightness and mode of use, so there is no universal figure valid for "a television" in general. The sensible decision does not require memorizing any specific value: if the device is not actually providing any real service to anyone, turning it off costs nothing; if it is about to be used again in a minute, turning every brief pause into a ceremony of switching off and on again makes no practical sense either.

The costliest waste combines three factors at once

The real impact of any energy-wasting gesture does not depend on a single isolated factor, but on the combination of three: the power of the device involved, the time it stays on without providing useful service, and the repetition of that same gesture across days and months. A very low-power device left continuously running for months can end up accumulating consumption comparable to, or even greater than, that of a much higher-power device that is only occasionally misused. That is why a priority rule based solely on a device's rated power, without accounting for how long and how often it runs unnecessarily, can lead to disproportionate effort spent on the wrong decision.

Think at the scale of the habit, not just the isolated gesture

The useful question is not "exactly how much do I save, today, with this gesture?" but "what would happen if this same habit were repeated systematically across every home in a neighborhood, or every classroom in a school, for an entire year?" That way of thinking helps distinguish a genuinely valuable habit from a well-intentioned but misdirected distraction, and avoids turning every small household decision into a disproportionate source of individual guilt compared with decisions of a far larger scale — a home's insulation, the climate-control system chosen, how often equipment that still works gets replaced — that in practice carry far more weight in the final outcome.

What to do first

  • Repair water leaks, especially hot-water ones, and cisterns that keep running.
  • Avoid heating or cooling empty rooms; keep filters and seals in good condition.
  • Reduce shower time before buying unnecessary "eco" gadgets.
  • Turn off unused screens and consoles; set up automatic sleep mode where the device allows it.
  • Wash with reasonable loads and cold water when the final result allows it.
  • Keep, repair and share equipment that still works: manufacturing the replacement also consumes energy and materials.

A household rule

Don't ask "how much do I personally save?" but "what would happen if this gesture were repeated in every classroom or home for a year?" Then check that the effort isn't masking a bigger decision: saving water while buying a new device every year is an incomplete kind of prudence.

The numbers, with their source

"Phantom" consumption can be a substantial share of the bill

The US Department of Energy (DOE) estimates that standby consumption from electronic equipment accounts for between 5% and 10% of residential electricity use in a typical American home, which can add 100to100 to 200 a year to the bill. Lawrence Berkeley National Laboratory places that same range at 5% to 10% in developed countries generally, though it acknowledges it can reach as much as 20% in some specific homes depending on the number and type of devices left permanently connected.

Sources: US Department of Energy; Lawrence Berkeley National Laboratory (LBNL).

Five minutes of a running tap, in liters

The EPA estimates that, for a typical American tap, leaving it running for five minutes while washing dishes can waste on the order of 38 liters of water. This is not a universal physical constant — the actual flow depends on the installed aerator's design and the network's pressure at that specific time and place — but it illustrates the order of magnitude of the hidden chain of capture, treatment, pumping and purification behind every liter.

Source: EPA WaterSense — Statistics and facts.

European standby limits, getting stricter over time

EU ecodesign regulation sets that, from 2025, no device may consume more than 0.5 watts in standby or off mode (0.8 watts if it displays information on screen), and that networked standby mode may not exceed between 2 and 8 watts depending on the product type. From 2027, those limits tighten further: 0.5 watts in standby, 0.3 watts in off mode, and a maximum of 7 watts in networked standby.

Source: European Commission — Ecodesign regulation on standby and off mode.

What this table is missing

None of these figures substitutes for measuring your own case: a specific home's real consumption depends on how many devices stay permanently connected, their age — newer devices already meet the stricter ecodesign limits — and habits that vary a lot from one home to another.

Sources

Household figures are examples, not universal labels. For a local decision, measure the actual flow, power and time involved.