6 min read

Electric boilers vs oil boilers for off gas grid heating

Electric boilers vs oil boilers for off gas grid heating

If you live in a home that is off the gas grid, you’ll know that there are a wide range of options available to choose from to heat your home. There are over 4 million homes in the UK which are aren't connected to mains gas and this number continues to rise with more people embracing self-sufficiency as well as the money saving benefits. In particular, oil boilers are one of the most common off gas grid heating options, but how do they compare with electric boilers?

In this heating blog, we’ll be looking at how oil boilers compare to their electric boiler counterparts. We’ll be covering:

•    How each type of boiler works
•    The pros and cons of each
•    How much they cost

So, if you are looking to change your non-mains gas heating system, then this blog will give you some insight into these two boiler options.

How each type of boiler works


Electric boilers

The way electric boilers work is not too dissimilar to gas boilers. Electricity is used to pass electric current through a heating element within the electric boiler which heats the water. When the cold water passes over the heating element, heat is transferred which results in hot water that can either be transported around your home or stored for use later. The way an electric boiler works, and stores water can vary depending on the type of electric boiler you install. These are:

  • Electric combi boilers: An electric combi boiler heats water on demand which uses more power than other types of electric boilers. However, they don’t require hot water storage cylinders which makes them a great choice for homes that have less space.

  • Electric flow boilers: Also known as ‘heat only’ boilers, electric flow boilers are best suited to larger homes that have a higher demand for hot water. If they are being used for both heat and domestic hot water, they will require a hot water tank to store the hot water for use when needed. The heated water is distributed throughout a home using motorised valves, pumps, and tanks. They can also be configured for heat only which does not require a water storage tank.

  • Electric system boilers: These contain the external components like a pump from a heat-only boiler system and include them in the body of the boiler. Electric system boilers don’t take up as much space because they only need a hot water tank. You’ll find that system boilers can vary, with some not requiring a hot water cylinder because it is integrated within the boiler which is designed to fit in smaller spaces.

ThermoSphere Electric Flow Boiler

Oil boilers

Just like electric boilers, oil boilers work like a gas boiler. All that is different is the fuel used. In the combustion chamber of an oil boiler, the fuel is ignited, and a heat exchanger warms up cold water, which can either be from the mains when using a combi system or if using a conventional system, the cold water will come from a tank. The heated water can be used for home heating and hot water.

The oil boiler requires a tank to store the oil until it’s required which is installed on the grounds of the property, but strict regulations need to be adhered to when storing oil. But more on that point further down in this blog.

Oil tank for oil boiler

The pros and cons of electric boilers


The pros of electric boilers

  • Great efficiency: Electric boilers provide heating and hot water much more efficiently than other boilers. In fact, they are almost 100% energy efficient. Because they don’t use any type of combustion, there are no loses through flue gases, which means you’ll use less energy to meet your heating requirements.

  • Less carbon emissions: Unlike oil boilers, electric boilers do not produce any carbon emissions, because they don’t burn any fuel. However, to make electric heating totally emission-free, the electricity used to power the boiler must be 100% from renewable sources such as wind or solar PV.
  • Minimal maintenance: Electric boilers have fewer moving parts than oil boilers which reduces the risk of faults and the need to purchase any annual service plans.
  • Flexibility for fitting: Electric boilers do not produce waste gas and because of this, they do not need a flue, which means that you have greater flexibility in choosing where to install it.
  • No risk of harmful leaks: Not only do you have no risk of an oil leak from an oil tank stored on your property, but you are also free from risk of an carbon monoxide leaks which can be created by faulty oil boilers.
  • Compact & quiet: Electric boilers are generally more compact which helps to overcome any installation challenges when space is at a premium. They are also much quieter when in operation because they do not burn any fuel.
  • Compatibility with existing heating systems: Electric boilers work seamlessly with existing heating systems such as wet underfloor heating, traditional central heating, and conventional room thermostats. You can also combine electric boilers with solar PV to reduce your reliance on your energy provider.

Reduce carbon emissions

The cons of electric boilers

  • Higher running costs: Excluding any regional variance of tariffs or the Energy Price Guarantee, the cost of electricity per kilowatt hour (52p) is much more than that of oil (10p to 15p). It is important to note that the prices of heating oil can fluctuate significantly.
  • Not suitable for all homes: Electric boilers are generally best suited for small to medium sized homes. According to the Boiler Guide, if you have one bathroom but ten plus radiators, there are better suited boilers to use rather than electric. This is because the energy needed can put too much demand on the incoming electrical supply.

Electric running costs

The pros and cons of oil boilers


The pros of oil boilers

  • Cheaper to run: Currently electricity is almost triple the cost per kW/hour compared to the price of oil. You can also stock up on oil when the price is at a lower point to save running costs a bit further.

  • Wider choice: When searching for oil boilers, there is a wider range to choose from compared to electric. However, with the government working towards reducing our reliance on fossil fuels and homeowners becoming more environmentally aware, it won’t be long before the scales are tipped in favour of electric with more innovations coming to market.
  • Models that can be installed outside: There are oil boilers that can be installed outside and provide multiple benefits such as freeing up internal space and noise reduction.
  • Good efficiency: As a fuel source, oil is efficient, so you get a good return on each unit of energy. According to Energyguide.org.uk oil boilers have a 93% efficiency.  However, they do not have the same level of efficiency as an electric boiler.

Energy Cost

The cons of oil boilers

  • Higher carbon emissions: Oil boilers release carbon into the atmosphere because they must burn oil. This isn’t good for the environment and can potentially put off potential buyers when you are looking to sell because the trend in more eco-conscious living is growing with pace.

  • Fluctuating oil prices: Recent events have highlighted the volatility of oil prices and with supplies of oil continuing to decrease, the price will continue to rise over time.
  • Space required: Unlike electric boilers, you don’t just need a space for the boiler to be installed, you also need space for the oil storage tank too. The tanks can be installed underground but with that comes more installation expense.
  • Risk of leaks: Failure to properly maintain the oil tank can lead to it leaking which is generally caused by corrosion. If this happens, a professional will need to come and clear up the oil and the tank will need to be replaced.

Oil leaks and prices

How much does each type of boiler cost?


Electric boilers

How much an electric boiler costs varies depending on the manufacturer and the type e.g. electric flow boiler vs electric combi boiler. Both lower output and smaller models will start from a price of around £600 to £1,000. Whereas larger and more powerful electric boilers could cost up to £2,500.

When looking at installation costs, if you are replacing an existing electric boiler the cost will be significantly less than replacing a gas boiler system. Installation costs will vary from installer so it’s worth getting three quotes to compare and check that you are getting a fair price. However, for reference, installation costs range between £500 and £1,000.

Oil boilers

The cost of an oil boiler depends on the type and the brand. For example, the cost of an oil combi boiler from Mistral can range from £1,700 - £4,600 (unit only). Whereas a regular oil boiler from the same manufacturer can range from £1,000 - £3,250 (unit only).

The installation costs for oil boilers vary. This is because not one installation is the same and it will also depend on if it is a simple replacement or brand-new heating system. With oil boilers there are more things to consider such us the position of the storage tank and the position of the flue, which makes installation costs higher than those of electric. For a ballpark figure, you can expect to pay between £500 and £2,500.

Should you choose an electric boiler or oil boiler?


The general rule of thumb tends to be that if your home has ten or more radiators and a large bathroom, oil boilers are probably the best fit and will cost less in terms of running costs. This is because most electric boilers can’t meet the demands of the home. For those that do, it will cost much more to run.

For everything else, electric boilers are a great option to take a closer look at. If you are also considering solar PV, electric boilers could be a no-brainer because installation is easier and running costs will almost be non-existent. 

Off grid_solar PV and electric heating

What next?


If electric boilers has whet your whistle and you want to find out more, explore our electric boiler pages

Alternatively, please contact one of the ThermoSphere team who will be happy to help.

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