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Types of Boilers


The boiler market has gradually changed over the years to cater to various needs. Boiler manufacturers have come up with different types of boilers depending on the type of fuel they use, their functionality and their features. When buying a new boiler for your home, you need to have ample information on all types of boilers so that you can select the best one for your home.

With so many options to choose from, it might feel slightly intimidating, but this guide on types of boilers should help you make the most out of the opportunity and buy the right boiler for your home.

Condensing and Non-condensing boilers

One of the terms you will encounter when searching for a new boiler is condensing and non-condensing boilers.

These terms describe a particular technology that determines how the boiler uses fuel to produce heat for your home. The choice between condensing and non-condensing boilers is not a difficult one.

Condensing boilers are more effective. They are sealed systems capable of extracting between 90 – 92% of the heat from the energy source. Condensing boilers get their name from their ability to extract heat from the flue gases.

Non-condensing boilers don’t have this feature. This type of boiler allows the flue gases to escape with the heat. Currently, most boilers in the market are all condensing boilers which reduces energy consumption and helps to trim down the energy bill.

Internal and external boilers

Before you jump further into the specific types of boilers, you need to decide whether you want the boiler inside or outside the house. Most boilers are installed in the home, especially in the kitchen cupboard. But, there are boilers that can be installed in the garage, outside in the garden or in an outhouse.

Deciding whether you want the boiler installed inside the house or outside will substantially impact the types of boilers you can select. You should also know that opting to install the boiler outside could impact the installation cost of the boiler.

Gas boilers

Gas is the most common energy source in the UK among boilers. Most of the homes around the UK are connected to the gas grid, making it a convenient source of energy and one of the more affordable. Needless to say, gas boilers also happen to be the most abundant in the market.

Advantages of a gas boiler

  • Cheaper to run – Gas is cheaper 3-4 times cheaper than electricity per kWh. It makes a more economical option that most homeowners would prefer to have a gas boiler than an electric option. However, electric boilers are more efficient (more on this later).
  • Gas is the cleanest fossil fuel – Natural gas (methane) is a fossil fuel. It is the cleanest of fossil fuels. It does create some carbon dioxide, but this is less than half of what is produced by oil and also less than what is produced by coal.

Disadvantages of gas boilers

  • You must be connected to the grid – The downside to gas boilers is that you must be connected to the gas network. If your home is not already connected, it can be expensive to connect. Also, some homes are in remote locations that make it impossible in the near future to be connected to the UK gas network.

Oil boilers

For homes that are not connected to the gas grid, oil boilers are an excellent alternative. Oil boilers don’t require you to be connected to any grid. With oil boilers, you only need to install a tank outside your home regularly filled with oil to power the boiler.

Advantages of an oil boiler

  • You don’t need a gas supply – Oil boilers make sense for homes that are not connected to a gas line. However, using oil to heat your home is more expensive than gas. It will make more sense to get access to gas if it is possible because it would save you more money in the long run.

Disadvantages of oil boilers

  • You can run out of oil – Unlike gas which is continually fed into your boiler from the national grid, the oil is put inside a tank. If you forget to refill the tank, the oil reserve can be depleted. You need to regularly monitor the amount of oil in your tank and order more at the right time.
  • Oil has to be for in bulk – Oil for your boiler can have financial constraints because the oil is ordered for in full. You need to make payment on delivery for a substantial amount of oil as opposed to paying monthly for what you spend.
  • You need extra storage space for the tank – Installing an oil boiler means you have to install an oil tank which requires space and additional financial commitment. The tank should be sunk underground. But if you want to have the tank above ground, there are several considerations like ensuring the ground is level, and there is a solid non-combustible platform for the tank to rest on.

LPG boilers

Liquified Petroleum Gas is a mixture of gaseous hydrocarbons produced from natural gas, oil extraction and oil refining. LPG is often stored and transported in small canisters, lorries and large tanks. Like oil, you will need to have a tank to store LPG inside your compound if you choose to use an LPG boiler.

Advantages of an LPG boiler

  • It’s cheaper than an oil boiler – If you’re after a gas alternative that doesn’t cost as much as an oil boiler to run, an LPG boiler is worth considering. LPG costs almost half the price of oil.
  • Cleaner emissions – Besides being affordable, LPG has a lower carbon footprint compared to oil. It produces about 15 – 20% less carbon.
  • More compact – LPG boilers are more compact in size than oil boilers. This is crucial if space in your home is premium. They also have a lower noise output making them ideal for indoor installations.
  • Wider variety – There are more LPG boilers in the market than there are oil boilers. Every leading brand has several models of LPG boilers, making it easier to find a boiler suited for your needs.

Disadvantages of LPG boilers

  • Higher running costs – LPG boilers cost more to run than gas or electricity. It could make more sense to have an electric boiler than a gas boiler if you’re connected to the electric grid.
  • You need to buy a tank – LPG requires a storage tank. You can buy or rent the tank from your supplier. The tank also requires installation, which will mean paying more for the new boiler.

Electric boilers

There are also electric boilers. These are known for their zero carbon emissions and high efficiency. They are perfect for homes looking for a compact boiler for a small household and also are a good alternative to gas boilers.

Advantages of an electric boiler

  • High efficiency – Electric boilers run at around 99% efficiency. They don’t lose as much heat as gas boilers which means you get more value for your money.
  • Cheaper to install – Electric boilers use a reasonably simple technology than other types of boilers. This makes them easy to install, and they don’t require accessories like a storage tank. They also don’t require a flue because they don’t produce the same toxic gases as gas boilers.

Disadvantages of electric boilers

  • High running costs –Although electricity is more affordable than LPG and oil, it costs more than gas. Its price is three to four times that of gas. Even with the highly efficient boiler, you will still have a high energy bill.
  • Not always ideal for large properties – Electric boilers are designed for small homes or homes that only need small amounts of hot water at a time. Electric boilers will often struggle to provide enough hot water for large properties because they don’t store the hot water.

Biomass boilers

Biomass boilers are an alternative to traditional gas or electric boilers. They work the same way but use different types of pipes, radiators and fuel. Biomass boilers run on wood pellets or wood chips which are burnt to heat a tank of hot water, which is then used for heating and providing hot water. This type of boiler is ideal for homes that are entirely off the grid, and the delivery of LPG and oil will be painstakingly high.

The Main Types of Boilers

All the above types of boilers fit into one of the following boiler types:

  • Conventional boilers
  • System boilers
  • Combi boilers

Conventional boilers

A conventional boiler is an old version of a system boiler. The conventional boiler requires a tank installed in your loft to feed the boiler, a hot water storage tank, and an expansion tank. Although it’s safe to say conventional boilers are outdated, they still have a place, especially in homes that have low water pressure.

Advantages of conventional boilers

  • They produce massive amounts of hot water, which makes them ideal for businesses and large households.
  • They are effective in areas with low water pressure.
  • Conventional boilers support the installation of a backup heater to allow for backup supply. This ensures you have hot water even if the main heater fails.
  • Conventional boilers work with the old radiators. If you don’t have the budget to overhaul the pipework and the radiators at the moment, the conventional boiler can fill in.
  • You can use renewable energy sources like solar thermal systems with the conventional boiler.

Disadvantages of a conventional boiler

  • The tank takes up a lot of space because of the additional tanks required for its installation.
  • Conventional boilers are harder to install. It will most likely reflect on the installation quote because of the three separate tanks.
  • The amount of water a household can use at a time is limited to the size of the hot water tank. After the water in the tank is depleted, you have to wait for the boiler to heat up some more.

Combi Boilers

Combi boilers are the most popular in the UK market. They are suited to most small to average-sized homes, and they are extremely efficient. The Combi boiler delivers heat and hot water on demand. They don’t require additional hot water storage, and they take their water directly from the feed.

Their compact nature makes them an ideal pick for most homes because the boiler can fit inside a kitchen cupboard. This also makes the boiler safer because it is away from prying eyes and curious hands, which contributes to how long combi boilers last.

Advantages of a combi boiler

  • It delivers heating and hot water in an instant and on-demand.
  • Every boiler brand in the UK has a combi boiler. All of them are compact, so you have a broad range of options to choose from.
  • You don’t need a water cylinder with combi boilers. Installation is easier, and you save on space.
  • Combi boilers are extremely energy efficient.
  • They are cheaper to replace than other options.

Disadvantages of a combi boiler

  • A combi boiler depends on the mains pressure. If the water pressure from the mains is too low, the boiler won’t work properly. Before installing a combi boiler, check what the mains water pressure is in your locality.
  • Limited use – Combi boilers are limited to small homes or homes that don’t require a lot of hot water.

System Boilers

Although most homes in the UK use a combi boiler, there is still a niche for system boilers. System boilers work the same way as a combi boiler. The only difference is they have a hot water cylinder that allows them to produce a lot of hot water.

System boilers are designed for homes with a high demand for hot water. Such properties have multiple taps and showers running at once.

Advantages of a system boiler

  • A system boiler can produce substantial amounts of hot water to keep up with the demand in the house.
  • The boiler doesn’t require a cold-water tank in your loft. It gets its water directly from the feed, saving you money in purchasing extra tanks and the installation work.
  • System boilers can be used with existing hot water cylinders, which cuts back on installation costs.

Disadvantages of system boilers

  • System boilers require more space than a combi boiler because of the cylinder.
  • The hot water tank requires insulation to prevent excessive heat loss and energy wastage. That means a higher installation cost.
  • The hot water isn’t supplied instantly. You need to wait for the tank to fill up before you can access it.

Final thoughts

Now you have all the information you need on the different types of boilers, their benefits, and their downsides. Finding the ideal boiler for your home and that matches your needs should be easier now.

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