Show the formula and working
This heating oil cost calculator works out what kerosene heating oil costs you per order, per year and per kWh of useful heat, for off gas grid homes in the UK, Ireland and the rest of Europe. Enter the litres you buy or the heat your home needs, your quoted price per litre and your boiler efficiency, and it shows the total, the cost of each kWh of heat and how many litres a year of heating takes.
Quick answer: Multiply the litres by the price per litre, then add 5% VAT if the quote excludes it. One litre of kerosene holds about 10.18 kWh, so at 90% boiler efficiency it gives about 9.16 kWh of heat. At an example 60p a litre, this heating oil cost calculator shows 2,000 litres costing £1,200, or about 6.55p per kWh of heat.
What Is a Heating Oil Cost Calculator?
A heating oil cost calculator is a tool that turns litres of heating oil, or a yearly heat demand in kWh, into a cost in pounds or euros and a cost per kWh of heat. In plain words: cost = litres x price per litre, plus VAT and any delivery charge. Heat = litres x kWh per litre x boiler efficiency. Cost per kWh of heat = total cost divided by that heat.
If you know the heat your home needs rather than the litres, the calculator works backwards: litres = heat needed divided by (kWh per litre x boiler efficiency). That is useful when an energy assessment gives you a yearly kWh figure, or when you want to compare oil with gas, electricity or a heat pump on the same basis.
How Do You Use the Heating Oil Cost Calculator?
- Choose Start from: litres of oil, for an order or a year of use, or heat needed per year in kWh.
- Enter Litres of oil, or Heat needed per year if you chose the heat option.
- Type your quoted Oil price per litre. The default is an example only, so replace it with your latest quote.
- Tick Quoted price excludes VAT (add 5%) if the supplier quoted a price before VAT, and add any Delivery or other charges per order.
- Set Boiler efficiency and leave Energy in one litre of kerosene at 10.18 kWh unless you have a figure from your supplier.
- Read the total cost, the cost per kWh of heat and the litres or heat, then open “Show the formula and working” to see each step.
How Many kWh Are in a Litre of Heating Oil?
One litre of kerosene heating oil contains about 10.18 kWh of energy, the conversion factor used by the Sustainable Energy Authority of Ireland (SEAI) for home energy calculations. Other sources quote slightly different figures, typically around 10 to 10.4 kWh, because some use the gross calorific value and some the net value. The difference is a few per cent, so the calculator lets you change it.
Not all of that energy reaches your radiators. A modern condensing oil boiler turns most of it into heat, while an older non condensing boiler loses more up the flue. At 90% efficiency each litre gives about 9.16 kWh of useful heat; at 75% it gives only about 7.6 kWh, so the same heat needs about 20% more oil. If your boiler is old and oversized, our boiler size calculator helps you check what output a replacement really needs.
How Much Heating Oil Does a House Use per Year?
Divide your yearly heat need in kWh by about 9.16 kWh of heat per litre, so a home that needs 15,000 kWh of heat a year uses about 1,640 litres of oil with a 90% efficient boiler. Real use depends on the size of the home, its insulation, the weather and how warm you keep it, so the best figure is always your own order history.
To find it, add up the litres on your delivery notes for the last 12 months and adjust for any change in the tank level between the first and last delivery. Choose “Litres of oil” in the calculator and enter that total to see your true yearly cost. If you are not sure how much oil is in the tank now, a dip reading and the tank’s dimensions will tell you.
Is VAT Charged on Heating Oil?
Yes, heating oil for domestic use in the UK is charged VAT at the reduced rate of 5%, not the standard 20%. According to HMRC’s VAT notice on fuel and power, any supply of 2,300 litres or less of kerosene, gas oil or fuel oil gets the reduced rate, and bigger deliveries also qualify when the oil is for domestic use.
Some suppliers quote prices excluding VAT and add it at checkout, while others show the price including VAT. Check the quote, then tick or untick the VAT box so the calculator matches what you will actually pay. Outside the UK, VAT or energy tax rules differ by country, so enter a price that already includes the tax you pay.
Is Heating Oil Cheaper Than Gas or Electricity?
At an example price of 60p a litre, oil heat costs about 6.55p per kWh, against about 8.86p per kWh of heat from mains gas at the Ofgem price cap average of 7.97p per kWh with a 90% efficient boiler. Oil prices move with world markets and can change a lot within months, so compare with your own quote rather than a single snapshot.
Direct electric heating at the price cap average of 26.32p per kWh costs far more per kWh of heat, but a heat pump delivers around three units of heat for each unit of electricity, which can bring its cost per kWh of heat close to or below oil. Our heat pump running cost calculator works out that figure, so you can put the two side by side. Gas standing charges and oil delivery minimums also affect the real comparison.
Heating Oil Cost per kWh at Different Prices
The table uses 10.18 kWh per litre and a 90% efficient boiler, so each litre gives 9.162 kWh of heat. The yearly cost column is for a home needing 15,000 kWh of heat, which takes about 1,637 litres. Prices are examples, including VAT.
| Price per litre | Cost per kWh of heat | Yearly cost for 15,000 kWh of heat |
|---|---|---|
| 50p | 5.46p | £818.60 |
| 60p | 6.55p | £982.32 |
| 70p | 7.64p | £1,146.04 |
| 80p | 8.73p | £1,309.76 |
| 90p | 9.82p | £1,473.48 |
Worked Example: A Winter Oil Order
Example: a rural cottage has a 90% efficient condensing oil boiler. The supplier quotes 62p per litre excluding VAT for a 1,000 litre delivery, with no delivery charge.
- Price with VAT: 62p x 1.05 = 65.1p per litre.
- Order cost: 1,000 litres x 65.1p = £651.00.
- Heat from the oil: 1,000 x 10.18 kWh x 90% = 9,162 kWh.
- Cost per kWh of heat: £651.00 / 9,162 kWh = 7.11p.
To reproduce this, choose “Litres of oil”, enter 1,000 litres and a price of 0.62, tick the VAT box and leave the other fields at their defaults. For more ways to cut heating costs, browse our heating calculators.
Heating Oil Cost Calculator FAQs
How do I work out the cost of heating oil?
Multiply the number of litres by the price per litre, add 5% VAT if the price was quoted without it, and add any delivery charge. For example, 1,500 litres at 60p including VAT costs £900. The calculator does this and also shows the cost per kWh of heat.
How long does 1,000 litres of heating oil last?
1,000 litres gives about 9,160 kWh of heat with a 90% efficient boiler. A home that needs 15,000 kWh a year would get through it in about seven months of average use, but far faster in midwinter, because most heating happens between October and March.
What is the difference between kerosene and red diesel?
Kerosene, also called 28 second oil, is the heating oil most UK and Irish homes burn in their boilers. Gas oil, often called red diesel, is a heavier 35 second oil used mainly by farms and older commercial burners. Use only the fuel your boiler is designed for.
When is heating oil cheapest to buy?
Heating oil prices follow world oil markets and demand, so there is no guaranteed cheapest month. Demand usually rises when the weather turns cold, so many households compare several quotes and order before winter. Buying a larger amount in one delivery can also lower the price per litre.
Does boiler efficiency change my oil cost?
Yes. A boiler at 90% efficiency turns each litre into about 9.16 kWh of heat, while one at 75% gives about 7.6 kWh. For the same warmth, the less efficient boiler burns about 20% more oil, which adds directly to your yearly bill.
Can I use this calculator outside the UK?
Yes. Switch the currency to euros and enter your local price per litre including any VAT or energy tax, leaving the UK VAT box unticked. The energy content of kerosene and the efficiency maths are the same in Ireland, Germany and the rest of Europe.
Checked October 2026. Sources: SEAI: One Stop Shop pre work energy usage conversion factors, GOV.UK: VAT on fuel and power (VAT Notice 701/19), Ofgem: Energy price cap unit rates and standing charges.