Heating your home – gas boilers briefly

Although the way how our houses are heated up is not often something we think about, it is a crucial element to consider. The most common option in England is a wet central heating system using natural gas. With this system, a gas-fired boiler heats water, distributing it around the property. In this way, hot water warms radiators and becomes available for use from taps and showers. If a house has no connection to the gas network, heating oil or occasionally LPG is most likely used as a fuel that feeds the whole system. As alternatives, we may point out biomass (wood) and electric boilers. A boiler is a serious investment for many years. The right choice should save you money, heat up your home efficiently, be eco-friendly and most importantly – suits your lifestyle and the type of house you live in. Let us take a look at the two most common boiler. With this simple guide, you can make a well-thought-out decision.

There are two main types of boilers to go with when renovating heating: combi and system boiler. You may also come across the term ‘conventional boilers’, but they are most likely to be found in older homes, so we will only focus on the first two.

Combination (‘combi’) boiler

The combi boiler combines central heating and hot water heating function in a single unit. Water is heated instantly within the boiler itself directly as it flows from the mains. Thanks to that, you can access hot water on demand, delivered at good pressure. It is a compact solution, relatively easy to install and maintain as all components are in one box. You heat as much water as you need, so there is no energy waste, making it an efficient and cost-effective option. The combi boiler will be, therefore, a good choice for smaller houses with limited space. However, if a dwelling has poor mains pressure, it will affect your home’s water pressure, which will be weak too. Before deciding on a combi boiler, check that your property has satisfying water pressure and an adequately sized water supply pipe. Otherwise, hot water service may not be adequate. For a similar reason of water pressure, a combi boiler may not work well for homes with more than one bathroom. Due to slower water flow when providing hot water to more the one outlet simultaneously, this system will have difficulty delivering hot water to two showers occupied at the same time. You may face dropping water pressure or seeing a temperature drop. If you have a larger house and family, you should consider choosing a system boiler.

System boiler

A system boiler, opposite to the combi boiler, delivers hot water from its external hot water cylinder, so naturally, you need extra space to accommodate the cylinder, which sits in an airing cupboard. The boiler takes cold-water supply from the mains, heats it up and then store the hot water in a cylinder in advance of use. The size of the cylinder actually determinants the amount of hot water available to use at a time. When it runs out, it simply needs some time and energy to fill up. In effect, you have to wait for the system to reheat and may not have how water when needed. It also brings a risk of heat loss as the hot water stays in the cylinder until you need it. Your cylinder must be well insulated to overcome danger. Also, with high hot water demands, it should not be a problem. The system boiler is better capable of delivering a large volume of domestic hot water than a combi boiler, for example, if you use two bathrooms at the same time. Moreover, if you use solar panels, the hot water cylinder can be modified to heat water using solar energy!

Condensing vs non-condensing boilers

When looking up types of boilers, you will probably come upon the following terms: condensing and non-condensing boilers. These terms describe the way a boiler operates, i.e. how the boiler uses fuel to produce heat for your home. Condensing boilers use technology that improves energy efficiency. Their design help provides the best possible performance with low running costs and reduced CO2 emissions. In England and Wales, all new installed gas-fired boilers must be high-efficiency condensing boilers except for exceptional circumstances.

Fuel – gas and other fuels

Apart from gas, your system can be feed with oil, LPG, electricity or biomass. Most boilers in the UK are gas boilers. It is a highly efficient, relatively cheap, and convenient way of heating. But it requires connection to the gas network and, therefore, it may not be available for everyone. For those off-grid properties, an oil-fired or LPG boiler may be an alternative worth considering. LPG is a more costly fuel than oil, but it is a better choice concerning availability and portability. It is also a more eco-friendly choice. Both would require a special storage tank that has to be replaced from time to time. If you do not want to monitor your boiler at risk you run out of fuel, you could opt for an electrical heating system. Electrical boilers do not require complicated installation and are fairly compact units. The running costs are pretty high, which makes these boilers out of reach for those on a tight budget. Finally, biomass boilers offer a fantastic heating solution with various options and different price ranges to choose from. The installation, including boiler price, can be very costly. On the bright side, the government financial incentives promote the use of renewable heat. You need to follow schemes and can get money towards renewable heating costs in your home. For example, Domestic Renewable Heat Incentive (RHI) or recently closed Green Home Grant. With the UK’s commitment to reach net-zero greenhouse gases emissions by 2050, being familiar with all the possibilities is a smart move. The government plans to ban new gas boilers, introducing a new Future Homes Standard in 2025 with energy-efficient standards of newbuild properties. As alternatives to gas boilers, a new generation of homes will require low carbon heating systems, including heat pumps, heat networks, hydrogen and direct electric heating.

Boiler size

Boiler size describes how much energy is generated by the boiler in the form of heat. The output is computed in kilowatts (kW). Basically, the higher are your heat and hot water demands, the more powerful boiler you need to meet them. A qualified plumber will help you calculate the optimal size.  The main facts to consider are the number of household members and the house size, especially the number of radiators and bathrooms. A too-small boiler may not be capable of heating all rooms evenly and providing enough hot water. On the other hand, an oversized boiler will produce excess energy, which is obviously damaging to your budget and harms the environment. For the average two beds with 5-6 radiators and one bathroom, you can go for a small 23-26 kW combi boiler. Substantially larger houses with several bathrooms that are used frequently at the same time will require a more powerful boiler installed, for example, a 33-35kW system boiler. It is always recommended to look for some advice from a specialist who will take into account other necessary indicators.


By choosing the right equipment and taking a proper heating approach, you can not only save money on your utility bills but also reduce environmental emissions and boost your house comfort! It is clearly worth taking a minute to think things through and make an optimum decision.