The short answer
Add cycle electricity cost, consumption-related water and wastewater cost, detergent and other entered consumables to estimate an included variable-cost subtotal. Keep each component separate. Missing prices remain excluded, fixed fees are not per-cycle savings, and water-heating energy already in a source must not be added twice.
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Define the costs you want to include
An electricity figure answers one useful question, but it is not the whole variable cost of a wash. The washing-machine and dishwasher tools now offer optional water, wastewater, detergent and other consumable fields.
They keep the original electricity result unchanged and show a separate subtotal of the costs entered. A blank means unknown or excluded; enter zero only when you know that component has no variable cost. Purchase price, repairs and fixed household fees remain outside this routine estimate.
Use the right water and energy units
A per-100-cycle energy label must be divided by 100 for one cycle. A litres-per-cycle water declaration already describes one cycle and should not be divided again. European label guidance distinguishes these bases.
Metered water charges may use cubic metres or thousands of gallons. The tools distinguish US and Imperial gallons and convert before applying a price. Keep tax and wastewater assumptions consistent. If your bill is unmetered or wastewater uses another volume basis, a simple variable rate may not describe a charge avoided by one fewer cycle.
Reproduce a documented dishwasher scenario
Bosch’s SMD6YCX01G product sheet declares 0.543 kWh and 9.5 litres for its eco cycle. Those are manufacturer values, not Watt & Home measurements. Now assume, purely for a worked budget, electricity at £0.28/kWh, water plus wastewater at £4/m³, detergent at £0.15/cycle and other consumables at £0.02/cycle.
| Component | Calculation | Per cycle |
|---|---|---|
| Electricity | 0.543 × £0.28 | £0.15204 |
| Water + wastewater | 9.5 ÷ 1,000 × £4 | £0.038 |
| Detergent | Entered dose cost | £0.15 |
| Other consumables | Entered allowance | £0.02 |
| Included subtotal | Sum before rounding | £0.36004 |
At five cycles/week over 52 weeks, the subtotal is £93.6104, displayed as £93.61. The electricity component remains £39.53/year. This difference reflects cost scope, not an error in the electricity calculation.
Calculate consumable cost per usable dose
Divide the pack price by its usable doses under your actual dosing routine. A £6 pack providing 40 usable doses is £0.15/dose. A manufacturer pack-count claim may not match a higher dose used for your water or load; choose the count that represents your routine.
Include rinse aid, salt or another consumable only on a consistent per-cycle allowance. A purchase made once in a month is not necessarily consumed entirely during that month’s cycles. Keep an accrual budget separate from cash spending.
Watch the hot-water boundary
Some source figures include associated water heating, while a socket measurement may exclude an external hot-water supply. The selected energy boundary must remain visible. Adding a water volume charge does not add heating energy, but adding another heating-kWh figure could duplicate it.
The optional-cost extension does not invent an external water-heating estimate. If that component matters and lies outside the energy figure, retain it as a separate documented scenario rather than declaring the subtotal a complete whole-house cost.
Compare the same task before choosing a programme
Different loads or cleaning outcomes are not interchangeable. Cost per cycle is useful for budgeting, while a purchasing decision also needs capacity, performance and installation context. Use the model library for traceable document inputs and programme-specific measurements for your own routine.