Do I need to replace my oil boiler? Re November 24, 2021

Do I need to replace my oil boiler?

Oil boiler tank

If you’re shopping around for a new oil boiler, no doubt you have many questions and concerns, especially after reading about the gas boiler ban and the Government’s plan to phase out the installation of fossil fuel heating in homes off the Gas Grid from 2026. 

Before you take the plunge, we’re here to help answer all your questions about the pros and cons of having an oil boiler, the installation costs and the future of oil boilers.

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

  • If you’re not connected to the Gas Grid, an oil boiler can be an excellent option as its fuel is affordable and accessible.
  • The oil boiler and tank are located outside of the house. This can free up space in your home.
  • 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! 
  • 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 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.
  • If your oil boiler is in an outbuilding, garage or shed it will serve to partially heat the building from heat loss.
  • 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.
  • 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.
  • 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.
  • Having an oil boiler installed for the first time is more expensive than installing a gas boiler.
  • Oil boilers are twice as bad for the environment as gas boilers in terms of carbon dioxide production.
  • 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 tube! 
  • 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.

Based on heating a standard 3-bedroom home, electricity is the most expensive alternative fuel source at £1,500 per year, followed by oil at £1,400 compared with gas at £700 – £1,400.

An oil boiler can be combined with solar thermal heating or solid fuel to lower the cost.

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. ​​The Government’s ambition is to set an end to the installation of fossil fuel heating in homes off the gas grid from 2026 (and non-domestic buildings from 2024).

It’s not hard to see the reasons why. A report published by the IEA (International Energy Agency) suggested that heating homes with oil or gas is responsible for about 20% of total carbon dioxide emissions in the UK and the US. (source: inews).

To tackle this issue, the UK Government has proposed the following plan: 

  • An end to the installation of new fossil fuel heating in homes off the gas grid from 2026.
  • A ‘heat pump first’ approach to replacement heating systems from 2026.
  • Introducing high performing replacement heating systems where heat pumps cannot reasonably practicably be installed.

There are concerns regarding the affordability of heat pumps. However, as part of the Heat and Buildings Strategy, the UK Government is setting an ambition of working with industry to reduce upfront costs of installing a heat pump by 25-50% by 2025 and to achieve cost parity between heat pumps and gas boilers by 2030.

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 to find out more.

When should I replace my oil boiler?

Generally speaking, an oil boiler could last for up to 15 years, or even longer if it is well maintained. Clearly, if your boiler stops working and can’t be fixed, you’ll have to replace it. However, there are many other less obvious signs that let you know that it’s time to say goodbye! Here are some warning signs;

  1. You’re seeing an unexplained rise in energy bills – naturally, boilers lose efficiency over time, which means your energy bills will go up regardless, but if your energy bills are creeping up out of control, this might be a sign that your boiler needs replacing. 
  2. Your boiler is leaking – while leaking doesn’t mean you have to replace your boiler, it is a sign that there are issues in one of the internal components. We recommend calling a heating engineer to check it out before it turns into something more serious.
  3. Frequent breakdowns – this happens a lot towards the end of the oil boiler’s lifespan and it may be time to start looking for other options. 
  4. The boiler fails to heat your home as it used to and doesn’t provide hot water as well. 
  5. Finding replacement parts for your boiler is a nightmare.
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