LPG vs oil boilers

For a household with no mains gas connection, the choice between LPG and oil is a choice between two delivered fuels with different storage, different combustion and different carbon profiles. Neither is piped in. LPG is delivered by road and stored in a tank rather than being piped directly into the home¹, and oil boilers have a storage tank that needs refilling every few months². Around two million UK properties are off-grid and depend on alternative fuels for heating and cooking³, and oil boilers alone serve an estimated four million homes with no access to mains gas⁴.

On carbon, LPG comes out ahead on the published figures. LPG emits 12% less CO2 than oil³, and 35% less CO2 than coal⁵. One industry source puts the coal comparison at 33% less CO2⁶. On running cost, the picture reverses: independent guidance describes LPG as the most expensive of the three fuel types when compared with gas and oil, while noting it has lower CO2 emissions than oil². An oil boiler usually costs hundreds of pounds a year more to run than its gas equivalent⁴.

The appliance and installation side is where the headline gap sits. Oil boiler installation runs from £500 up to £2,000 across all three oil boiler types⁷, and LPG installation is described as significantly cheaper than electric, oil and air source heat pumps⁵. Both fuels remain legal for off-gas-grid homes in England, where the proposed ban on installing oil and LPG boilers was delayed from 2026 to 2035⁸.

LPG or oil: what off-grid households are choosing between

Off-gas-grid homes use a range of fuels: heating oil, liquefied petroleum gas, solid fuels, mains electricity and microgeneration¹¹. Of these, natural gas is the most common boiler fuel nationally, followed by heating oil and, less frequently, LPG¹². In Scotland, around 87% of households use a gas or oil-fuelled boiler¹³, which shows how far oil reaches into the housing stock even where gas is available.

LPG is a mixture of propane and butane, two colourless liquids that heat homes¹⁴. It is the fuel of choice for 193,000 homes⁵, and an LPG boiler is found in rural properties considered off grid¹⁵ and is best suited to rural locations with no mains gas connection¹⁴. Oil boilers, by contrast, serve an estimated four million homes with no mains gas access⁴.

The two fuels are not interchangeable at the appliance level. LPG has variants of combi, system and open-vent boilers available¹⁵, and LPG system and open-vent boilers require a separate hot water tank¹⁵. LPG also fuels the familiar domestic gas appliances: central heating boilers, gas fires, gas ranges, AGAs and cookers³. Oil does not offer that breadth of appliance choice, which matters if a household wants a range cooker or a gas fire as well as central heating.

For energy independence, both fuels keep a household off the mains gas grid but leave it dependent on a road delivery. LPG is stored in a tank outside the property and topped up by an LPG supplier¹⁵; oil needs a tank refilled every few months². Neither is a self-generated fuel. The independence is from the gas network, not from a supplier.

Running costs: LPG is the dearer fuel, oil the dearer appliance

The running cost comparison is not close on the published guidance. LPG is described as the most expensive of the three fuel types when set against gas and oil². A modern condensing gas boiler is usually the cheapest to run compared with oil, electricity, LPG and house coal for homes with a mains gas connection², which sets the benchmark the off-grid fuels are measured against. An oil boiler usually costs hundreds of pounds a year more to run than its gas equivalent⁴.

That leaves LPG and oil as the two most expensive common options, with LPG at the top of the range and oil below it. The gap is not quantified in the published figures, so the ranking is directional rather than a number a household can budget from.

On the appliance side the position flips. LPG installation is significantly cheaper than electric, oil and air source heat pumps⁵. Oil boiler installation costs vary from £500 up to £2,000 across all three oil boiler types⁷, and oil boilers can be more expensive than electric ones due to higher installation costs¹⁶. The £500 to £2,000 figure is the installation labour and fitting, not the boiler itself.

For a household weighing the two, the trade is between a higher fuel bill and a lower installation bill, or the reverse. Neither fuel is a route to lower running costs than mains gas. Both are a route to heating a home that the gas network does not reach.

Flame control and day-to-day operation

LPG burns as a gas, which changes how the appliance behaves day to day. LPG is a cleaner fuel compared to oil as it burns less carbon, preventing soot and ash build up¹⁵. That soot and ash is what an oil boiler accumulates over a heating season, and it is part of why oil appliances need regular attention.

Noise is the other practical difference. LPG boilers do not produce as much noise compared to oil boilers when the heating is on¹⁵. That claim comes from a manufacturer rather than an independent test, so it is reported rather than measured, but it matches the engineering: an oil boiler carries a burner and a pump that an LPG boiler does not.

Leak detection favours LPG as well. LPG is not odourless, making it easier to detect leaks⁶. Oil leaks announce themselves differently, through smell and staining around the tank and pipework rather than through an added odorant in the fuel.

On controls, the regulatory direction of travel is the same for both. For oil fired boilers installed as a replacement of an existing boiler, time and temperature controls are applied as a new additional requirement¹⁷. Time and temperature control should be installed for the heating system on a gas-fired boiler in an existing dwelling, whether new or replacement¹⁷. The same control expectation therefore lands on an LPG boiler as on an oil one.

Efficiency standards for the two fuels diverge in the building regulations. A worked example in Approved Document L Volume 1 uses an LPG boiler with emissions of 0.241kgCO2/kWh and primary energy of 1.141kWhPE/kWh at 93% efficiency¹⁸. For gas fires in combined fire and back boiler units, the minimum efficiency is 45% for natural gas and 46% for LPG gross calorific value on an inset live fuel-effect unit¹⁹. A separate official consultation gives 63% for natural gas and 64% for LPG on all types except inset live fuel-effect¹⁹. The two documents disagree on the figure and the conflict is unresolved.

Appliance and installation costs compared

Oil boiler costs break down by type, and the published figures are specific. A heat-only oil boiler runs £1,200 to £2,450 for the unit, with an average total cost of £3,075 including installation⁷. A system oil boiler runs £1,450 to £2,375, with an average total cost of £3,163⁷. An oil combi runs £2,025 to £2,825, with an average total cost of £3,675⁷. Installation across all three types is £500 to £2,000⁷.

For comparison, a gas heat-only or conventional boiler is quoted at £2,500 to £4,100 installed, for larger properties with greater demand and low water pressure⁴. Oil boilers are quoted at £3,300 to £4,000 installed for properties with no access to mains gas supply⁴. Those two figures sit in the same independent guidance and show how little separates oil from gas on installed cost, even though the running costs differ sharply.

No equivalent published price table exists for LPG boilers. LPG installation is described as significantly cheaper than electric, oil and air source heat pumps⁵, which is a relative statement rather than a figure. LPG boiler prices are installer-quoted, and a household comparing quotes should expect the appliance, the flue, the tank connection and any controls to be itemised separately.

The VAT position matters for anyone considering a switch. Dual-fuel boilers designed to burn coal or oil as well as wood are not covered by VAT relief²⁰. That relief applies to qualifying energy-saving materials and grant-funded heating supplies, and the exclusion of dual-fuel appliances is a specific carve-out.

Storage, tanks and what each fuel needs on your property

Both fuels need space outside the house, and both are governed by separation rules. Requirement J6 states that liquid fuel storage systems and the pipes connecting them to combustion appliances shall be so constructed and separated from buildings and the boundary of the premises as to reduce to a reasonable level the risk of the fuel igniting in the event of fire in adjacent buildings or premises²¹. That requirement applies to fixed oil storage tanks with capacities greater than 90 litres and fixed LPG storage installations with capacities greater than 150 litres located outside the building²¹.

For LPG specifically, tanks and associated pipework connecting the system to a combustion appliance should be designed, constructed and installed in accordance with the requirements set out in the UKLPG Code of Practice 1: Bulk LPG Storage at Fixed Installations²². A tank not exceeding 1.1 tonnes needs 3 metres of separation from buildings, boundaries or fixed sources of ignition²³.

Oil has its own regime, covered in more detail on domestic heating oil tanks. Oil boilers have a storage tank that needs refilling every few months². LPG boilers need the tank refilled periodically, depending on how much is used². Neither fuel removes the delivery dependency: LPG is delivered by road and stored in a tank rather than being piped directly into the home¹.

The practical difference is scale and frequency. An oil tank typically holds a season's worth of fuel and is filled a few times a year. An LPG tank is topped up by a supplier on a schedule that depends on consumption¹⁵. Both need a road tanker to reach the property, which is the constraint that defines off-grid heating more than the fuel itself.

Switching fuels: conversion kits and dual-fuel boilers

Converting an existing oil boiler to LPG is not a standard route. Independent guidance states that some boilers designed for mains gas can be converted to use LPG¹, which is a different starting point: a gas boiler with an LPG conversion kit, not an oil boiler with a new fuel line. An oil boiler has a different burner, a different fuel delivery system and different combustion characteristics.

What does exist is dual-fuel appliances. Some makers sell boilers that run on natural gas and LPG with the conversion kit included as standard, marketed on the basis that no other manufacturer offers this²⁴. That is a new appliance rather than a conversion of an existing oil unit, and it gives a household the option to move between the two gases without replacing the boiler.

For a household on oil, the realistic switch is to a new appliance, whether LPG, a heat pump or another fuel. Households with an oil boiler, LPG, electric radiators or storage heaters may save money on energy bills by switching to a heat pump²⁵. That is the official position on the direction of travel, and it is where the grant money points.

The evidence on satisfaction is mixed. Households that had previously had working gas or oil boilers were more equivocal and more likely to report an increase in bills or lower satisfaction than their previous system when moving to a heat pump²⁶. That finding comes from official research and is worth weighing against the grant incentive.

The Boiler Upgrade Scheme grant for off-grid homes

The Boiler Upgrade Scheme provides upfront capital grants to support the installation of heat pumps and biomass boilers in homes and non-domestic buildings²⁷. For off-gas-grid properties, the grant level is higher. The scheme offers £9,000 off the cost and installation of air-to-water or ground source heat pumps in eligible off-gas grid properties¹⁰, and £9,000 towards an air-to-water or ground source heat pump for eligible off-grid properties heated by LPG or oil²⁸.

The conditions are specific. The heating system being replaced must be fuelled by either oil or liquefied petroleum gas²⁹, and the previous heating system being replaced must be fuelled by oil or LPG for the uplifted grant³⁰. Fossil fuel heating systems for the purposes of the scheme include oil, gas, electric or liquefied petroleum gas³¹. One approved grant category is a ground source heat pump in an off-gas grid property that is replacing an oil heating system³².

The timing matters. The uplifted grant value for off gas grid properties will be in place until 31 March 2027³⁰, and applications for uplifted grants for eligible off-gas grid properties can be made on or after 21 July 2026³⁰. The wider scheme has been extended to 2030³³. Uptake has been weighted towards off-grid homes: as of November 2025 around 39% of such grants had been made to homes off the gas grid³⁴.

The scheme is open to domestic and small non-domestic properties³⁵, and installers must be registered to carry out the work³⁶. For a household on oil or LPG, the grant is the single largest financial lever available, and it points away from both fuels rather than between them.

Where LPG and oil both fall short

Neither fuel is a route to energy independence in the sense of generating heat on site. Both depend on a road delivery, a storage tank and a supplier. LPG is the most expensive of the three fuel types², and oil boilers usually cost hundreds of pounds a year more to run than gas⁴. Both carry the storage and separation requirements set out in Requirement J6²¹.

The regulatory direction is also the same for both. The proposed ban on installing oil and LPG boilers, and new coal heating, for off-gas-grid homes in England was delayed from 2026 to 2035⁸. That delay applies to England; Scotland has consulted separately on its own heat in buildings proposals²¹, and Wales and Northern Ireland have their own building regulation and grant arrangements, covered on boiler and heating grants in Wales and boiler and heating grants in Northern Ireland.

For a household weighing the two, the honest summary is that LPG is cleaner and quieter and costs more to run, oil is cheaper to run and costs more to install, and the grant money now favours replacing both with a heat pump. The wider context sits on heating a home off the gas grid and home heating and energy independence.