In a part of the world that gets as cold as the UK does, a boiler is the most important single appliance in the home — but it is also poorly understood
Most of us set the thermostat and then don’t give a second thought to the boiler — until it breaks down, at which time we pay someone else to look at it.
But when it comes to replacing your boiler, improving the energy efficiency of your home, or saving a bit of money, it pays to know what your options are.
Different types of boilers and boiler brands
The boiler market in the UK is dominated by one particular type of boiler: the condensing boiler.
However, there are different types of condensing boiler, including combi-boilers, heat-only and system boilers. Popular brands producing combi-boilers include Baxi and Glow Worm (both Baxi heating boilers and Glow Worm boilers are British made). It is also worth noting that combi-boilers come in all sorts of shapes and sizes and one type of Glow Worm boiler, for example, may differ substantially from another.
While most condensing boilers use mains gas, there are some alternatives for those who live off-grid, or just want a different option. Oil boilers, for instance, typically use kerosene that is delivered to your home. But having an oil boiler comes with its own challenges (see below).
Meanwhile, a wood boiler (otherwise known as a biomass boiler) is yet another alternative. Let’s look at all the different types in-depth, and their advantages and disadvantages.
Condensing boilers are by far the most common boiler type in UK homes, and are far more energy-efficient than older mains gas boilers, using around 90% of their heat.
A condensing boiler works by passing hot gas through a central chamber that heats up water but, cleverly, a second chamber uses remaining heat to warm up water coming back into the unit from the heating system.
Of all the condensing boiler types, the combi-boiler is the most popular. A combi-boiler includes the hot water unit and cold water tank in the same unit, which means all your hot water and heating come from the same unit. This makes it easy to install.
It also means you get a steady supply of hot water through your taps as you don’t have to wait for the tank to fill and don’t have to worry about lots of space for different tanks. The downsides lie in the fact that, as they are a small unit, you will only get maximum pressure through one tap at a time, and they struggle to produce large quantities of hot water.
Heat-only boilers, in comparison, have a more traditional approach by offering hot water only, whilst cold water is supplied separately. This does away with some of the problems of supply and water pressure. But, because the hot- and cold-water systems are separate, they take up more space, and are less energy-efficient.
Oil boilers represent an alternative to the estimated four million homes across the UK that are not connected to mains gas. This isolation comes at a cost however, and an oil boiler will typically be a few hundred pounds a year more expensive to run than gas.
In terms of the mechanics, oil boilers are fairly similar to traditional boilers. Instead just using oil rather than gas to heat the inner pipes and, thereby, the water.
The main difference comes in when you try and get your hands on the oil itself. The oil has to be delivered to your home, making oil boilers more logistically challenging. Prices do also vary for heating oil or kerosene, so you may have to shop around to get a good deal.
Maintenance can also be an issue because, if you run into any problems, you will need to get an Oftec registered engineer in to inspect it (rather than a Gas Safety Register engineer for conventional gas boilers).
A biomass boiler, or wood boiler, is the other main alternative and, as the name suggests, relies on wood pellets, chips or logs to generate heat. Wood pellet boilers are very cheap in comparison to the other alternatives, costing an estimated £600 a year to run, and are energy-efficient.
The carbon dioxide given off by wood pellet boilers is similar to that absorbed by new plants, so it is a sustainable fuel. Pellets are the most practical solution for biomass boilers even though logs are cheaper, as they can be automatically fed in to the system. You will have to find a supplier for your pellets though. The Energy Saving Trust estimates installation costs between £7,000 and £13,000, and a tonne of wood pellets can cost under £200.
They emit around 3 tonnes fewer of carbon dioxide a year compared to a gas boiler, but there are some things to be aware of.
Unlike gas or oil boilers, a wood pellet boiler will generate ash, so you will have to empty it out approximately once a week. The ash may be self-cleaned depending on the boiler, but if you don’t keep it clean it could shut down.
Biomass boilers tend to be slightly bigger than gas or oil boilers and you will also need somewhere to store the heating fuel. Likewise, you will need a flue or chimney, which may mean you need planning permission, so be sure to check the regulations for your property in advance. You will also need to maintain the flue pipe or chimney to keep it clean of soot deposits.
HETAS, the official biomass body, recommends you do this about twice a year. You will also need to make sure your flue or chimney is clear of debris or bird’s nests.
So, which boiler is right for you?
Choosing the right boiler is tricky, but whether you go for gas-powered combi boilers like Baxi boilers or Glow Worm boilers, or if you go for an oil boiler, or a biomass boiler, the decision will more often than not come down to what is suitable for your property. The main issues are:
- How much space do you have available?
- Are you on mains gas?
- How big is your property?
- Will you need planning permission for a flue or chimney?
- Is it easy to find an oil or wood pellet supplier in your area?