Is heating oil cheaper if you order more?

How much you save per litre

Here is today's typical gap, using Fueltool's median prices, which include delivery:

Check how much your tank can take

Which? says domestic tanks are typically 1,000 to 3,500 litres and should only be filled to around 80% to 90% of their capacity, to avoid spills. To work out a safe order:

1. Find the tank's capacity, often on a label on the tank or in its paperwork.
2. Take 80% to 90% of that figure.
3. Subtract what is already in the tank. Our guide on checking your tank level explains how.

What is left is the most you should order. If you aren't sure of the capacity, see oil tank sizes.

When a smaller order makes more sense

• Cash flow. A bigger order means a bigger bill at once. The CMA found payment plans widely available across the UK, though not always clearly signposted, and Citizens Advice suggests putting a little aside each month to spread the cost. See spreading the cost of heating oil.
• Price timing. A big fill locks in the day's price for longer. Government energy statistics note that it is typical for consumers to buy in bulk when prices are low; filling right up when prices are high means living with that price until your next order.
• Tank space. Never order more than the safe space. No saving per litre is worth an overfilled tank and a spill.

Share a delivery with neighbours

If your own tank is small, you can still get some of the benefit of buying in bulk by buying at the same time as others nearby. Citizens Advice says joining an oil club, where people in your area buy heating oil at the same time, might save you money, and that you can set one up if there isn't one locally. Which? says joining a heating oil club is free, and that if you start your own you'll need a coordinator to contact oil companies and negotiate a price. See whether oil clubs save money.

Very large orders and VAT

For homes, VAT stays at 5% whatever the size of the order. Under HMRC's rules, any delivery of up to 2,300 litres to one site on one day gets the reduced rate whatever the oil is used for. Above that, the reduced rate depends on the oil being for a qualifying use, which includes domestic use, rather than applying automatically.

Which? also notes that the tanker used in your area holds 5,000 to 23,000 litres, and that a combined order bigger than that is less likely to get a discount because the supplier will need a second vehicle. That mainly matters for oil clubs and other very large orders.

To see the gap for your own address, compare prices for your postcode at 500 and 1,000 litres.