Documentation of our claims
Last updated 8 October 2026. The water figures are calculated. We keep a log of every wash, and the figures are updated once a full year of logs exists.
Whenever we state a figure about water, steam or products on renmester.no, a small raised number follows it. That number points here. This page sets out the basis for each claim, where it comes from, which sources it rests on, and what it does not say.
The page exists for three reasons. The Norwegian Marketing Control Act (§§ 6–8) prohibits misleading marketing, and a business that makes a claim about its own services must be able to document it. The Norwegian Consumer Authority’s guidance on sustainability claims in marketing (updated 17 September 2026) says the documentation must exist before the claim is published, and that general environmental words do not hold up without concrete, documented content. And we have a rule of our own: every figure we use is explained in one place, so you can check the arithmetic yourself.
The status says where a figure comes from. Calculated means worked out from the figures in the table below. Documented means it rests on an independent source. Measured means it comes from our own log.
The figures we work from
- The steam cleaner
- Professional steam cleaner: 2 250 W, 4 bar, 145 °C, 2 litres of water on board
- Physical ceiling for steam
- 3.6 litres of water an hour, even if every watt went into steam
- Pre-rinse when needed
- Hand sprayer on salt, slush and clay, normally 1–2 litres, on top of the steam
- The comparison: garden hose at home
- 300 litres per car (the sources give 180–500 litres)
- Conservative comparison: pressure washer at home
- 75 litres per car (Danish Environmental Protection Agency)
- Saved per car
- 296 litres against the hose, printed as «around 300»; 71 litres against high pressure
- Capacity
- 5 cars a day, 365 days a year
- Saved a year
- 540 200 litres against the hose, printed as «over 540 000»; 129 575 litres against high pressure
- Electricity per car
- Up to 2.25 kWh
Water per car, method by method
| Method | Litres per car | Source and note |
|---|---|---|
| Steam wash by Ren Mester (our method) | < 4 | Physical ceiling for our machine, claim 1 |
| Bucket and sponge at home | 30–100 | CCW/Waterwise 30 l, Sydney Water 99 l |
| Pressure washer at home | 72–79 | Danish EPA, measured |
| Nordic Swan labelled hall | < 90 | Label requirement; 80 % recycled |
| Hall with water recycling | 50–70 | Fresh water per car, Swedish EPA |
| Garden hose at home, Nordic study | ≈ 100 | Danish EPA, normal pressure |
| Garden hose at home | 180–500 | Sydney Water 180, CCW 300, LCRA ≈450, UB ≤500 — we use 300 |
| Hall without recycling | 250–400 | Swedish EPA |
Claim 2 compares with a garden-hose wash at home, 300 litres. The conservative comparison, with a high-pressure wash at home, gives around 70 litres saved per car and over 125 000 litres a year (129 575 litres calculated).
The claims
- 1Under 4 litres of water per car
- 2Around 300 litres less per car than a garden hose
- 3Over 540 000 litres a year
- 4Less wash water where the car stands
- 5Eco-labelled products where they exist
- 6Steam instead of harsh chemicals in the home
- 7Electricity, not «climate neutral»
Under 4 litres of water per car
As it appears on the site
A steam wash uses less than 4 litres of water per car.
Basis
We wash the exterior with a professional steam cleaner (2 250 W, 4 bar, 145 °C, 0.5-litre boiler and 1.5-litre tank). Physics sets the ceiling: 2 250 W for one hour is 8.1 MJ, and turning one litre of water into steam takes 2 257 kJ. Even if every watt went into steam, the machine cannot use more than 3.6 litres per hour, and an exterior wash takes under an hour. The machine carries 2 litres of water (boiler and tank), so in practice it is one to two fills per car. The ceiling is calculated, not metered; we keep a log and will update the figure with measured values.
What the claim does not say
Applies to the steam in the exterior wash. On very dirty cars (road salt, slush, clay) a hand-sprayer pre-rinse comes on top, normally 1–2 litres. Seat treatment and interior deep cleans use their own equipment and water.
Sources
Around 300 litres less per car than a garden hose
As it appears on the site
That is around 300 litres less water per car than a garden-hose wash at home.
Basis
Washing at home with the hose running is the most common way to wash a car, and the most water-hungry. Water utilities and consumer bodies put it at 180–500 litres per wash: Sydney Water 180 litres, the UK Consumer Council for Water (CCW, with Waterwise figures) 300 litres, the Lower Colorado River Authority about 450 litres, the University of Barcelona up to 500 litres. We use 300 litres, in the lower half of that span. 300 litres minus under 4 litres is around 300 litres saved per car. Against a high-pressure wash at home (72–79 litres measured by the Danish Environmental Protection Agency) the saving is around 70 litres per car, and that figure is in the table on this page too.
What the claim does not say
If you wash with a bucket and sponge (30–100 litres) or a pressure washer (around 75 litres), the difference is less than 300 litres. The comparison is with washing at home, not with car-wash halls: a modern hall with recycling uses 50–70 litres of fresh water per car according to the Swedish EPA, and the Nordic Swan requires under 90 litres for a labelled hall.
Sources
- Consumer Council for Water (UK): How much water do you use? — hosepipe car wash 300 l, bucket 30 l
- Sydney Water: Water use and conservation — hose wash 180 l, bucket 99 l
- Canadian Car Wash Association, citing Lower Colorado River Authority — driveway wash 120 gallons (450 l)
- Universitat de Barcelona (OSSMA): Car washing — hose up to 500 l per wash
- Miljøstyrelsen (DK): Bilvask — vandforbrug ved manuel vask og højtryk
- Naturvårdsverket (SE): Fordonstvätt — vattenförbrukning per tvätt
- Svanemerket: Fakta om bilvask
- Uno-X: Svanemerket bilvask — under 90 liter per vask, 80 % gjenbruk
Over 540 000 litres a year
As it appears on the site
Over 540 000 litres of water saved a year.
Basis
The arithmetic: 296 litres saved per car (300 litres with a garden hose minus under 4 litres with steam) × 5 cars a day × 365 days = 540 200 litres. We print «over 540 000» so the sentence stays true on days that run short. Five cars a day is the capacity we plan for; in periods with fewer cars the saving is correspondingly lower. Measured against a high-pressure wash instead of a hose, the figure is around 125 000 litres a year.
What the claim does not say
This is an annual capacity calculation against a garden hose, not a figure measured over a full year. It is updated once a full year of logs exists.
Sources
Less wash water where the car stands
As it appears on the site
Less wash water on your driveway — car wash water can carry oil, heavy metals and road dust.
Basis
Norwegian municipalities warn against washing cars on the driveway because the water carries oil and fuel residue, heavy metals from brakes and tyres, and road dust, and because it runs into storm drains untreated. With under 4 litres of steam instead of hundreds of litres from a hose, a fraction of the wash water is left at your address.
What the claim does not say
We say «less», not «none»: some water and dirt reaches the ground with steam too. We do not claim steam washing is exempt from local rules on car washing.
Sources
Eco-labelled products where they exist
As it appears on the site
Eco-labelled products wherever a good alternative exists.
Basis
For paint, interiors, floors, bathrooms and kitchens we choose products carrying the Nordic Swan or the EU Ecolabel whenever a labelled product does the job. The labels set requirements for biodegradability, toxicity and dosing, verified by an independent third party.
What the claim does not say
For iron removal on paint, tar and insect removers and acid-based wheel cleaners there is no labelled alternative that works. There we use the smallest effective amount and rinse thoroughly. We do not claim that everything we use is eco-labelled.
Sources
Steam instead of harsh chemicals in the home
As it appears on the site
Steam at 145 °C loosens grease, limescale and soap residue, so we manage with milder products and less of them.
Basis
The same steam cleaner is used in most of our home jobs: tiles and grout, shower glass, taps, cookers, vents, skirting and window frames. Steam at 145 °C softens limescale and grease mechanically and thermally, so the surface can be wiped clean without strong chemicals left to work. The result is fewer products in use, lower dosing and less residue left in the room.
What the claim does not say
Some surfaces do not tolerate steam (untreated wood, certain painted surfaces, electronics), and mould, burnt-on grease and some stains still need a product. We do not claim that steam disinfects or kills any particular share of bacteria.
Sources
Electricity, not «climate neutral»
As it appears on the site
The steam cleaner uses electricity, up to 2.25 kWh per car. We do not call steam washing climate neutral.
Basis
A 2 250 W heating element for one hour uses 2.25 kWh. That is true, and it is stated here so that a claim about water is not read as a claim about climate. We chose steam for the water and for what does not run into the drain, and we say it that way.
What the claim does not say
We have not calculated the climate footprint of a steam wash against a high-pressure wash, and we make no claims about CO₂.
Sources
Think a figure here is wrong, or want to see the log? Get in touch and we will answer with what we have. How we wash with steam is described on the steam cleaning page.