If your current oil boiler is over 15 years old, frequently breaks down, or is no longer energy-efficient, then yes, it may be time to replace it.
With the UK government planning to ban the installation of new fossil fuel heating systems in off-grid homes, now is the ideal time to assess your options.
In this guide, we’ll explore when you should replace an oil boiler, what it might cost, the pros and cons of sticking with oil, and what the future holds for oil heating in the UK.
What is an oil boiler?
Most households in the UK use gas-fired boilers to heat up their homes and provide hot water. However, around 4 million households in the UK aren’t connected to the Gas Grid. Of these 4 million households a range of alternative heating types are used, including LPG, oil, solid fuels, electricity and solar.
An estimated 1.1 million homes in the UK currently run on oil heating. Oil heating is also referred to as a ‘wet’ system because it burns fluid (oil). The oil boiler fuel is more affordable than electricity and LPG , therefore, it’s a popular alternative for suburban homes.
How does an oil boiler work?
You’ll find that an oil boiler works in a similar way to a gas boiler.
To summarise how an oil boiler works, the water is supplied directly from the mains (if you have a combi or system boiler) or from a cold-water tank kept in the attic (if you have a conventional boiler.)
The fuel, in this case oil, gets ignited in the combustion chamber and a heat exchanger warms up the cold water. The heated water is then used in your radiators, to provide heating, and it also runs through the taps and showers to provide your home with hot water.
The main difference between a gas boiler and an oil boiler is the type of fuel they use and the way the fuel is stored. A gas boiler gets its fuel from the Gas Grid, while an oil boiler comes with an oil tank that is stored on your property and there are certain installation regulations that need to be followed.
The tank is usually refilled when it reaches a quarter full to ensure that you don’t run out of heating oil and to avoid the impurities running through the heating system.
The types of oil boilers
Just like a gas boiler, there are 3 different types of oil boilers; combination, system and conventional. Here is how they work.
Combination boiler
A combi boiler combines hot water and heating in a single unit.
Combi boilers are connected directly to the mains water supply coming into your home, they heat this water directly, eradicating the need for a separate water tank (as with a system or regular boiler). The water is then pumped from the boiler to the radiator or taps to provide you with heating and hot water on demand.
System boiler
Just like a combi boiler, a system boiler gets its cold water directly from the mains. However, the system boiler stores hot water in a separate storage tank from the boiler.
This means that you can get heating and hot water instantly when you need it. On the downside, the cylinders could run out of hot water which means you’ll have to wait for it to fill up again – in the freezing cold!
Conventional boiler
Conventional boilers work slightly differently from a combination boiler. Rather than heating water directly from the mains water feed as is the case with combi boilers, a conventional boiler will have a large cold water storage tank (usually in the attic or loft) where it will receive water from the mains supply.
The cold water feeds down from the attic or loft into the boiler where it is heated by the boiler’s heat exchanger and then pumped to a hot water cylinder, where it is stored ready for use. Just like the system boiler, the cylinders could run out of hot water which means you’ll have to wait for it to fill up again – did we mention in the freezing cold…!
Oil boilers pros and cons
| Pros | Cons |
|---|---|
| If you’re not connected to the Gas Grid, an oil boiler can be an excellent option as its fuel is affordable and accessible. | If you have limited outdoor space for a large oil tank, then perhaps an oil boiler isn’t the right option for you. The tank also needs to be easily accessible for refilling otherwise you may have to install an expensive pipe run to get to the tank. |
| The oil boiler and tank are located outside of the house. This can free up space in your home. | Oil prices can fluctuate depending on the market. This is also true for other fuel sources, but oil is more volatile as there are more factors that affect the price and there is no official regulation. |
| Due to your boiler and the tank located outside of your house, servicing the boiler is less disruptive to your daily life as your boiler can be fixed, replaced and refuelled without your home being turned into a workshop! | The fuel supply needs to be physically delivered. This means there is the chance of delays, human error in an order, traffic or forgetting to order in time. Newer oil tanks have sensors that can automatically place an order when you get down to a certain level. |
| Although carbon monoxide poisoning has become much rarer due to improved safety measures, there is still a chance of a leak causing symptoms. Having your boiler located outside eliminates this risk. | Having an oil boiler installed for the first time is more expensive than installing a gas boiler. |
| Having an oil boiler located outside means that should the boiler leak or malfunction, there is less chance of it causing damage to your property, compared to a gas combi boiler located in your airing cupboard leaking. | Oil boilers are twice as bad for the environment as gas boilers in terms of carbon dioxide production. |
| If your oil boiler is in an outbuilding, garage or shed it will serve to partially heat the building from heat loss. | An oil storage tank can be an eyesore if it isn’t placed underground or tucked out of the way. It will ruin your view when you’re sitting in your hot tub! |
| The flow rate of an oil boiler is usually lower than that of a gas boiler. | |
| The boiler and tank are located outside of the house, which means there is damage that comes with weather exposure; cold, frost and rain. This can cause components to rust or malfunction. |
The environmental impact of oil boilers
Regulations introduced in 2007 meant that all condensing oil boilers must have an energy efficiency rating of 86%+. Nowadays, most modern oil boilers attain an energy efficiency rating of 92%+.
On the other hand, oil boilers are worse for the environment than gas boilers, because burning oil produces twice as much carbon as gas.
If you’re looking for environmentally-friendly heating solutions, you might want to have a look at heat pumps, hydrogen boilers, microwave boilers and electric boilers. Each has its own advantages and disadvantages, so read our overview here.
Oil boilers installation costs
The cost of installing a new oil boiler varies depending on a range of factors that determine the complexity of the job. On average, oil boiler installation can cost between £800 to £2,000. In addition to that, you’ll need to factor in the cost of the boiler, oil tank and all the other appliances as well.
For that hefty price, it’s always a good idea to shop around to get the most bang for your buck. Make sure to choose an OFTEC registered engineer to carry out the job.
Oil boiler running costs
Domestic oil prices are tied to the price of crude oil, so they can fluctuate with demand, availability and even political situations. Oil prices are also affected by demand, so the prices will increase during winter.
In terms of how oil prices compare against other fuel types – it’s more expensive than gas (per kWh) and LPG but cheaper than other alternative fuel sources on the market such as biomass and electric.
When it comes to heating a standard 3-bedroom UK home, electricity is by far the most expensive option, with average annual costs of £1,600–£1,800 due to its higher price per kWh. Oil and gas are currently the most cost-effective fuels, with heating oil typically costing slightly less or similar to mains gas depending on market prices.
Electric heating: £1,600–£1,800 per year
Heating oil: £1,200–£1,400 per year
Mains gas: £700–£1,200 per year
These figures can vary based on the efficiency of your boiler, insulation levels, and local fuel prices. However, if your oil boiler is old or inefficient, you could be paying more than necessary — making replacement a smart financial and environmental decision.
The future of oil boilers
The UK has pledged to reduce carbon emissions to zero by 2050 and become a carbon-neutral nation. With one-third of the UK’s CO2 emissions coming from heating our homes, it’s clear that to achieve the carbon-neutral target, change is coming to the heating industry.
In the Heat and Buildings Strategy, the government has set out its intention to phase out all fossil fuel-based heating systems, including oil.
To be more specific, the plan will start by phasing out fossil fuel systems in homes that aren’t connected to the Gas Grid.
Should I get an oil boiler installed?
If your house is connected to the Gas Grid, a gas boiler is always our first recommendation.
However, if your home is off-grid, an oil boiler will be your best bet. Oil is cheaper than other alternative fuel sources on the market such as biomass wood pellets and electricity.
If you’ve decided to buy an oil boiler, just keep in mind that you’ll need to keep an eye on the amount of oil in the tank and make sure that it doesn’t run out. After all, nobody likes a cold shower!
You’ll also need to consider the accessibility of your property as oil will be delivered by a huge lorry when you’re getting topped up. Don’t forget too that the oil tank should be safely stored on your property and should meet the safety requirements. This will be assessed by an OFTEC registered engineer.
Oil boiler installers
Whether you choose a local company, energy supplier or an online company like WarmZilla to install your boiler, you should always check that the installer is OFTEC (Oil Firing Technical Association) registered, this is the oil certification equivalent to Gas Safe registered for gas boiler installations.
It is not a legal requirement to be OFTEC registered to fit an oil boiler, it is a ‘ competent person scheme ‘ meaning you can buy with more confidence.
Any OFTEC registered installer has completed an approved training course and passed an assessment. They are periodically reassessed to ensure they are maintaining standards and are up to date with current best practices.
Upon completion of your oil boiler installation, an OFTEC registered installer will provide you with an official certificate to confirm that the work done meets industry standards. You don’t need to get the work checked by your local authority.
Did we mention that all WarmZilla engineers are OFTEC registered?! Just email us at ask@warmzilla.co.uk to find out more.
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