1. The short answer
A smaller heating oil order almost always costs more per litre than a bigger one, because fixed delivery and handling costs are spread across fewer litres, and some suppliers simply will not deliver a partial order at all below a set floor. BoilerJuice, a large UK oil broker, will not take an order under 500 litres, though the exact surcharge that would apply just below that line is not published (BoilerJuice Help Centre, accessed 18 September 2026).
That does not make a full tank automatically the right call for every household. It changes the trade-off you are making: a full tank locks in today's rate for more litres, while a partial fill keeps your options open for the next order, at the cost of paying a higher rate per litre this time and possibly again on the next delivery.
2. Why the price per litre moves with order size
A delivery driver's time on site, the truck's running cost and a supplier's minimum handling fee are largely the same whether the tank takes 500 litres or 3,000, so a bigger order spreads that fixed cost over one trip, one vehicle and one plannable run rather than several. Sellers describe this as their reasoning for lower per-litre rates on larger orders, according to both HeizOel24 and FastEnergy (heizoel24.de, fastenergy.de, accessed 18 September 2026), but the size of any such discount, and whether one is offered at all, varies by dealer and by day: our own check of fastenergy24.com on 18 September 2026 found no discount whatsoever between 1,000 and 3,000 litres. Treat the mechanism as the reason sellers give, not as a fixed, documented saving.
A full-tank order and a season-long fixed price contract solve a related problem from different directions. One buys a large quantity now at a rate fixed for that delivery; the other fixes a rate for a season's oil regardless of when each delivery actually lands. Our fixed price contract glossary entry covers that second route, including who carries the risk if the market moves after you sign.
3. The numbers: one documented pricing example
The table below is the only tiered, dated pricing example found for this page: quotes from a single German portal, fastenergy24.com, that happen to fall on three different days rather than one, so it shows what one seller charged for different volumes rather than a clean, same-day quantity scale.
| Order size | Price | As of | Source |
|---|---|---|---|
| 1,000 litres | 139.41 EUR/100 L, about 1,394 EUR total | 17 September 2026 | fastenergy24.com |
| 2,000 litres | 139.41 EUR/100 L, about 2,788 EUR total, the same rate as the 1,000 L quote taken a day earlier | 18 September 2026 | fastenergy24.com |
| 3,000 litres | 139.41 EUR/100 L, the same rate as 1,000 and 2,000 litres; an earlier quote of 109.78 EUR/100 L on 7 September 2026 is superseded | 18 September 2026 | fastenergy24.com |
| 3,000 litres, independent comparison | 181.0 cents/litre | 17 September 2026 | Tecson |
| Minimum order, United Kingdom | 500 litres; nothing smaller is delivered | accessed 18 September 2026 | BoilerJuice Help Centre |
Treat the fastenergy24.com rows as one seller's example, not a market-wide scale. Checked again on 18 September 2026, the 1,000, 2,000 and 3,000 litre prices at this seller were identical, 139.41 EUR/100 L; the lower 109.78 EUR/100 L figure once shown for 3,000 litres was an earlier, superseded quote from 7 September 2026, not a documented volume discount. Quantity discounts vary by dealer and by day, and on some days they do not exist at all, exactly as this checked example shows; treat the mechanism below as the reason sellers give, not as a discount you can count on. Whatever size you settle on, our days of supply glossary entry explains how to turn the litres you hold into a number of heating days.
4. Why timing risk cuts both ways
A partial-fill strategy is a bet on which way the price moves before your next order, and this page takes no side on that bet: it can save you money if prices fall and cost you money if they rise. On 17 September 2026, German retail heating oil averaged 181.0 cents per litre at Tecson, up 16.8% on the week and 90.3% on the year, a level Tecson says only March 2022 has exceeded. A rising market like that punishes a household that ordered a small amount and has to come back for the rest at a higher rate; a falling market rewards the same behaviour.
Supply conditions can move the odds further against a small, late order. When distillates run short, minimum quantities and lead times both tend to lengthen for smaller buyers, a pattern our diesel shortage glossary entry documents with dated inventory figures. Seasonal fuel changes add a second timing pressure: several European markets switch diesel to a winter cold-weather specification on a fixed autumn date, covered in our winter diesel glossary entry, and suppliers juggling that changeover alongside a wave of top-up orders is one reason delivery windows can stretch in late autumn.
5. What this means for your own order
There is no "right" order size without first estimating how much oil your household will actually use, and the standard starting point is last year's consumption, not a market forecast. Suppliers scale an expected delivery using the ratio of heating degree days in the current period to heating degree days in the same period a year earlier, at the same weather station: expected delivery is roughly last year's consumption multiplied by that ratio. Our heating degree days glossary entry explains the formula and its different base temperatures; the sources checked for that page found no single, sourced "typical annual" figure for any market this site covers, so neither page will invent one, and you should not either without your own local weather data.
Once you have an estimate, a workable rule of thumb, not a price call, is this: if your remaining litres cover fewer heating days than your supplier's current lead time, a fuller order carries less delivery risk, because it avoids paying twice for fixed delivery costs and avoids a second order landing during a possible minimum-quantity or peak-season squeeze. If your tank still holds a comfortable buffer, a smaller top-up can make sense, provided you accept that the next fill may land at a higher or a lower rate than today's. How much you should actually keep in reserve depends on more than order size alone: it also depends on your tank's capacity and on how long the oil can be stored without degrading, covered in our heating oil shelf life glossary entry. Our heating oil, buy now or wait page weighs that timing question against current market conditions in more depth. You can put your own consumption and tank numbers into our fuel cost calculator to compare order sizes for your own bill.
Work out your own order size from your consumption, not a guess.
Run the calculator6. What this term does not mean
Partial fill and order size is not the same question as group buying, even though both promise a lower price per litre. A minimum order quantity, such as BoilerJuice's 500 litre floor, is a rule a supplier sets for one household's delivery. A minimum participant count or combined volume in a group scheme is a separate rule governing several households ordering together, covered on its own terms, including the joint-liability risk a partial-fill order does not carry, in our group buying glossary entry.
A second common mix-up is treating the lowest price per litre as automatically the lowest bill: a bigger order at a better rate still costs more cash today and ties that money up until it is burned as heat. A third is assuming a fixed, official percentage exists for how much of a tank's rated volume can actually be filled or drained; the sources reviewed for this page describe a technical base amount left behind by a suction pipe or shut-off sensor, but none supplied a single official percentage, so this page does not state one. If you need to know your own tank's usable capacity, that is a question for a certified installer, since rules on tank inspection and filling vary by country and municipality.