Homemade vs shop-bought oat milk: the honest cost calculation

A litre of homemade oat drink costs you 60 to 80 g of oat flakes plus a few centimes of electricity. Take the price on your own packet, divide the kilo price by twelve or fifteen, and you have your ingredient cost per litre. In almost every case it lands far below the carton.

That calculation, which is the one most articles on this subject stop at, leaves out three things that change the conclusion. Homemade is not fortified, and that is not a cosmetic detail: the carton supplies calcium, usually B12, sometimes iodine, and no blender will reproduce any of them. Straining throws away part of what made oats nutritionally interesting in the first place. And the homemade version keeps for two or three days, which sets a production rhythm that plenty of people abandon after three weeks.

This guide does the full calculation, without inventing prices, and says at the end who the homemade route is genuinely worth it for.

How to work out your real cost without kidding yourself

The per-litre cost of homemade oat drink comes down to three lines. Most articles stop at the first one.

The raw ingredient

This is the easy line. A decent drink needs 60 to 80 g of flakes per litre. Below 50 g the result is watery and separates within hours. Above 100 g the texture turns thick and the straining yield gets worse.

Ingredient cost per litre = kilo price of flakes × 0.07 on average. A packet at 3 francs a kilo gives roughly 21 centimes a litre. An organic packet at 6 francs a kilo gives roughly 42 centimes. Use the price actually on the shelf where you shop: the ranges quoted from memory in blog posts are unverifiable and usually out of date.

Energy and water

A blender draws somewhere between 300 and 1500 watts and you run it for one minute. A minute at 1000 watts is 0.017 kWh, a fraction of a centime at Swiss tariffs. Tap water for a litre is similarly negligible. The real energy line is not the blending, it is the fridge holding the bottle cold for three days. That is still small, but it is not zero, and saying so is more honest than pretending the energy cost does not exist.

Losses and time

This is the line nobody counts. Straining holds back pulp, and that pulp contains oats you paid for. Depending on how fine your strainer is and how hard you press, you lose between 10 % and 25 % of the dry matter you put in. Throw the pulp away and your real ingredient cost rises by that much. Use it in porridge or biscuit dough and it costs nothing at all.

Time does not convert into francs honestly, because ten minutes taken from an evening are not worth the same as ten minutes taken from a working morning. Count in frequency instead: a homemade drink keeps three days, so two or three production sessions a week if you drink it regularly. That number, rather than the cost per litre, decides whether you will stick with it.

What the sum comes to

Homemade stays cheaper, often by a factor of three to five on ingredients alone. No hidden cost line reverses that gap. But the price gap is not the interesting question, because the two products are not the same product. That is what the rest of this article is about.

One framing note, since price is the topic: in the only published survey I could find, covering the ten largest UK supermarkets, the 191 plant-based drinks studied cost on average 64 % more than the 195 dairy milks compared, at £1.95 a litre against £1.19 (Current Developments in Nutrition, 2025). Put plainly, if price is your only criterion, neither the carton nor the homemade version beats cow’s milk. Homemade is a saving against the plant-based carton, not against the dairy aisle.

What actually separates a carton from a homemade bottle

Price is not the main difference. Four industrial operations have no domestic equivalent, and they explain both the taste and the nutrition label.

Enzymes

Look at the ingredient list on several oat drinks sold in Switzerland: alongside water, oats, oil and salt you will often read “enzymes (amylase, amyloglucosidase)”. Those enzymes cut the oat starch into shorter sugars. That is what gives the carton its naturally sweet taste with no sugar added, and it is also what stops it thickening into a gel.

At home, with no enzyme, blending releases some starch but does not cut it. Two consequences follow: your drink is noticeably less sweet, and it tends to turn slimy.

Homogenisation

A carton passes under high pressure, which breaks up the fat droplets and disperses them durably. Your blender does not. That is why a homemade drink separates within hours in the bottle and why you have to shake it. Adding a tablespoon of neutral oil improves the body in the mouth but does not replace homogenisation.

Heat treatment and sterility

A UHT carton keeps for months at room temperature because it was taken to high temperature for a few seconds and then filled in a sterile environment. Your bottle has had none of that. It contains tap water, the flora of the flakes and the flora of your hands, and it keeps two or three days in the fridge. That is not a quality difference, it is a difference in kind.

Fortification

This is the most important point and the one homemade guides handle worst. It gets its own section.

What the homemade version does not contain, and who that matters for

An oat drink, carton or homemade, is not nutritionally equivalent to cow’s milk. The comparative analysis published in NPJ Science of Food in 2023 found this across every plant base studied: protein, fat, amino acids and minerals all sit lower than in cow’s and goat’s milk, the single exception being soya, which comes close on protein.

The difference is that the carton compensates by fortification and your blender compensates for nothing.

Calcium

A fortified plant drink contains calcium at a level comparable to milk, generally around 120 mg per 100 ml. That is an addition, not a natural content. The analysis of 138 UK plant-based beverages published in Food Research International in 2025 confirmed that fortified versions match milk on calcium while remaining below it on potassium, zinc and iodine.

Your homemade version contains a negligible amount. If you drink three large glasses a day thinking you are covering part of your 700 mg daily requirement (NHS), you are mistaken. That calcium has to come from elsewhere, which is entirely doable but has to be deliberate: see our guide to calcium and magnesium without dairy and the one on balancing calcium without dairy products.

Iodine

This is the worst-covered nutrient and almost nobody mentions it. A survey of UK supermarkets carried out every year from 2020 to 2024 and published in the British Journal of Nutrition in 2026 identified 466 plant-based alternatives in 2024. Among non-organic milk alternatives, 48 % were fortified with iodine, against 88 % for calcium and 71 % for B12. More than one carton in two therefore contains no iodine at all, and organic ones almost never do, since fortification is heavily restricted in organic production. Even when fortified, those drinks supplied 75 to 83 % of the iodine content of cow’s milk.

Adults need 140 micrograms of iodine a day, and the NHS notes that some plant drinks, soya or oat, are fortified with it and advises checking the label (NHS). A homemade drink contains none whatsoever. If you eat neither fish nor dairy, iodine becomes a genuine issue, covered in our article on avoiding iodine deficiency without fish.

Vitamin B12

No plant produces it. It appears in cartons only because it was added, in 71 % of cases according to the survey above. Homemade contains zero, with no possible exception. See our guidance on B12.

Protein

Oat drinks sold in Switzerland declare between 0.4 and 1.1 g of protein per 100 ml, against roughly 3.4 g per 100 ml of cow’s milk. Homemade sits at the bottom of that range. This only matters if the drink was doing duty as a protein source, which is never a good plan: see our guide to plant proteins instead.

The sugar story, and why the label surprises people

Take a carton of oat drink with no added sugar and read the nutrition table: you will often find 4 to 7 g of sugars per 100 ml. Across the Swiss products listed in open composition databases, the spread runs from 0 g for fermented or reformulated versions up to around 6.8 g per 100 ml. No sugar was added. Those sugars come from starch cut up by the enzymes described above, mostly maltose, the disaccharide produced by starch hydrolysis.

Here is the point that matters: those sugars count as free sugars. The definition adopted in the UK since the SACN Carbohydrates and Health report covers all mono- and disaccharides added by the manufacturer, cook or consumer, plus those naturally present in honey, syrups and unsweetened juices. Sugars locked inside the cellular structure of a food are excluded, but starch released and hydrolysed from a milled grain is no longer inside that structure.

The NHS reference points are 30 g of free sugars a day for adults, 24 g at ages 7 to 10, 19 g at 4 to 6, 14 g at 2 to 3 and 10 g at age 1. Half a litre of an oat drink at 6 g per 100 ml delivers 30 g, the entire adult allowance. That is not a scandal, it is information the label already gives and nobody reads.

Where does that leave your homemade bottle? Without added enzymes, hydrolysis is far more limited, but it is not zero: oat flakes carry their own amylases, and blending with lukewarm water activates them. That is in fact the real reason some homemade batches taste oddly sweet after twenty-four hours in the fridge. Blending with cold water keeps it in check.

On label reading more broadly, see how to read a food label as a vegetarian and our piece on the glycaemic index from a plant-based angle.

Beta-glucans: the argument that drains away with the pulp

Oats contain beta-glucans, a soluble fibre carrying the only solid health claims in this whole file. Two official conditions give the order of magnitude.

The Swiss ordinance on food information (FIO, SR 817.022.16) permits the claim on maintaining normal blood cholesterol for a food containing at least 1 g of oat or barley beta-glucans per portion, provided the consumer is told the effect is obtained from 3 g a day.

On blood glucose, EFSA concluded in 2026 that a cause-and-effect relationship is established between oat beta-glucans and the reduction of the post-meal glucose peak, based on sixteen human intervention studies, provided the food supplies at least 3 g of beta-glucans per 30 g of available carbohydrate (EFSA Journal, 2026). A useful calibration point: the year before, the same authority refused to lower that threshold from 4 g to 2 g, because the effect was not consistent at that dose across 21 studies and 59 trial comparisons (EFSA Journal, 2025). The dose matters.

The grain itself is a modest and variable source. Measurement of 93 Swedish and 41 American oat samples found extractable beta-glucan contents ranging from 0.76 % to 3.68 % (Journal of Agricultural and Food Chemistry, 2005). Across 70 g of flakes that is between 0.5 and 2.6 g before processing. Then you strain, and part of that fibre leaves with the pulp.

The practical conclusion is unwelcome but clear: oat drink, homemade or industrial, is a poor source of beta-glucans. If you want them for their effect, eat the oats rather than drinking them, as porridge or as soaked raw flakes. Our whole grain cooking guide has the proportions.

That said, swapping milk for oat drink is not without measurable effect. A pilot randomised trial published in Nutrition Journal in 2026 followed 33 young women drinking 600 ml a day of either oat drink or semi-skimmed milk for four weeks: the oat group saw total cholesterol fall by 0.3 mmol/l and LDL by 0.4 mmol/l relative to the milk group. It is a pilot, on a small sample, over four weeks, in healthy young women. Treat it as a signal, not a demonstration.

Making it properly, and above all avoiding the gel

The recipe fits in four lines, but every failure comes from the same thing: starch.

The method

For a litre, use 70 g of oat flakes, 1 litre of cold water and a pinch of salt. Blend for 30 to 45 seconds, no longer. Strain through a nut milk bag or a fine cloth, pressing moderately. Bottle, refrigerate, shake before each use. Optional: a tablespoon of neutral oil for body, one pitted date for roundness.

Why it turns slimy

Blending releases starch from the flakes. That starch swells and gels as soon as it meets heat or prolonged agitation. Three rules avoid it: cold water, short blending, and no subsequent overheating. Heating a homemade oat drink for a latte thickens it every time, which the industrial version avoids because its enzymes have already cut that starch up.

The raw oat question

You are consuming uncooked cereal here, so it is worth knowing what that means. Shop-bought oat flakes are not raw flour in the strict sense: the industrial process, known as kilning, applies steam and then drying before rolling. A 2024 study showed that saturated steam at 90 °C for thirty minutes followed by drying at 100 °C for thirty minutes is enough to inactivate the grain’s lipases, without which lipase activity climbs during storage and the product goes rancid (Foods, 2024). That treatment is not sterilisation, but it puts flakes in a different category from raw flour.

Raw flour is another matter. Analysis of 200 bags of Swedish retail wheat flour found shiga toxin genes in 12 % of samples, with organic, wholemeal and small-scale production making no significant difference (Access Microbiology, 2023). In practice: do not substitute raw oat flour for flakes, and wash your equipment as you would after handling any uncooked preparation.

Keeping it

Two to three days in the fridge, in a clean sealed bottle, and trust your nose. A homemade drink that smells sour or has thickened unusually goes on the compost. This is not about waste: it is a non-sterile, non-acidified preparation with no preservation barrier of any kind.

If you make other plant drinks, the logic is identical: see homemade plant milks without a machine and our piece on additives in plant milks.

The environmental case: the real gap is not the one you think

The three environmental arguments for homemade are packaging, transport and the absence of processing. All three are real and all three are small. The large environmental gap is not between your bottle and the carton, it is between plant drinks and cow’s milk.

According to the Our World in Data synthesis drawing on the Poore and Nemecek meta-analysis, which covered more than 38,000 farms across 119 countries, cow’s milk emits around three times more greenhouse gases, uses around ten times more land and two to twenty times more freshwater than plant-based alternatives, per litre (Our World in Data). The same source adds a caveat campaigning articles tend to skip: no plant alternative wins on every metric at once, and a litre of plant drink is not nutritionally comparable to a litre of milk.

Once you have switched to plant-based, the remaining gap between homemade and carton comes down to one piece of packaging and a few lorry kilometres. That is a decent reason to make your own; it is not a major climate argument. Our article on the carbon impact of plant drinks compared with cow’s milk sets out the comparison.

One point beats all three of the usual arguments: the pulp. It represents 10 to 25 % of the material you bought. Reusing it in porridge, biscuit dough or bread dough genuinely lowers your cost per litre and removes a waste stream at the same time.

Children, where the priorities invert

For a healthy adult eating a varied diet, the choice between homemade and carton is a matter of budget and convenience. For children, the priorities invert.

The NHS states that unsweetened, calcium-fortified plant drinks can be given from the age of 1 as part of a balanced diet, and that no rice drink should be given before the age of 5 because of arsenic (NHS). The operative word in that sentence is “fortified”. A homemade drink is not.

A review published in Deutsches Ärzteblatt International in 2026 gives a useful order of magnitude: across comparative cross-sectional and cohort studies, each daily cup of plant drink in five-year-olds came with a height-for-age z-score lower by 0.04 and a BMI-for-age z-score lower by 0.06, corresponding to roughly 0.2 cm and 0.1 kg. The authors stress the complete absence of randomised trials and long-term follow-up, and the limited methodological quality of the available data. So this is not demonstrated causation. But given the uncertainty, a homemade drink, lower in energy density and carrying no fortification, is the wrong candidate for replacing a meaningful share of a young child’s intake. That decision belongs with a paediatrician, not a blog post.

Six mistakes that come up constantly

Counting the blender as a cost. If you buy one specifically for this, the write-off swamps the saving for two years. If you already own one, it costs nothing. Both situations exist, but they do not belong in the same sum.

Assuming homemade is richer because it is less processed. It is poorer: no added calcium, no B12, no iodine, fewer beta-glucans once strained.

Blending longer to extract more. What you mostly extract is starch, and what you get is gel.

Using hot water. Same effect, worse.

Treating oat drink as a protein source. It is not one, carton or homemade.

Keeping a bottle beyond three days. There is no acidity, no preserving sugar and no heat treatment protecting you.

Adapting to your situation

You drink half a litre a day or more. Homemade pays off and the annual gap is real. Cover calcium, iodine and B12 elsewhere, deliberately.

You use a splash in your coffee once a week. The saving is trivial and a production session every three days makes no sense. Buy a fortified carton.

You consume no dairy at all. Fortification stops being a detail. A carton fortified with calcium, B12 and iodine does a job your blender never will. Combining often works best: homemade for cooking, a fortified carton for whatever genuinely replaces milk.

You want foam for a cappuccino. Industrial barista versions are formulated for it, with acidity regulators that stabilise the foam under steam. Homemade foams poorly, and adding oil helps the body rather than the foam.

You are coeliac. Oats are frequently contaminated with wheat during growing or milling. In Switzerland, the food information ordinance requires that oats in products labelled gluten-free have been specially produced and processed to avoid that contamination, with a gluten content not exceeding 20 mg/kg (FIO). Ordinary loose flakes carry no such guarantee.

Limits of the available data

Three uncertainties remain.

Swiss retail prices. The major retailers’ websites block automated price collection, so approximate prices cannot be quoted reliably. A calculation method will remain more useful than a price table that would be wrong in six months.

The exact composition of your own drink. Beta-glucan and sugar levels depend on the oat variety, the fineness of the flakes, the water temperature, the blending time and the mesh of your strainer. The ranges quoted here come from published measurements on grain samples and commercial drinks, not from an analysis of your bottle.

The health effect of the swap. The only recent randomised trial available covers 33 women over four weeks. That is thin. The literature lacks long trials comparing a fortified oat drink against milk under real conditions.

Frequently asked questions

Is homemade oat milk genuinely cheaper? Yes, on ingredients, by a factor of three to five depending on what your flakes cost. The gap narrows if you bin the pulp and if you have to buy a blender for the purpose.

Why is my homemade version less sweet than the carton? Because the carton uses enzymes that cut starch into sugars. Without enzymes you do not get that taste, which is not a fault.

Should I soak the flakes first? Not necessary, and a long soak at room temperature raises the risk of souring and encourages starch release. If you do soak, do it cold and for no more than one night.

Can you heat homemade oat drink? Yes, but it will thicken. Heat gently, never boil, and accept the texture.

How long does it keep? Two to three days in the fridge, in a clean bottle.

What do I do with the pulp? Next morning’s porridge, biscuit dough, bread dough, or the base for vegetable patties. It keeps two days cold or freezes in portions.

Can a homemade drink replace milk for a child? It is the wrong product, precisely because it is not fortified. Ask a paediatrician rather than an article.

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