Boiler Types and Efficiency

Most homes in the UK are heated by either a furnace or boiler. Furnaces are designed to heat and distribute air throughout the house, typically using a system of ducts. Boilers produce hot water, using either the hot water, directly, or steam for heating. With a boiler, hot water is distributed by baseboard radiators, a radiant floor system or heat the air with a coil. Steam boilers distribute steam through pipes to radiators. Because it operates at a higher temperature, a steam boiler is typically less efficient than a hot-water boiler. A combi boiler provides both central heat and doubles as a high-efficiency water heater. The use of a Baxi combi boiler is becoming a popular way to heat a home.

Types of Boilers

Regular Boiler

Regular boilers, also knows as conventional, heat-only or open-vent boilers, operate as part of a heating system with a hot-water storage cylinder, a cold-water storage tank and a feed and expansion tank. Regular boilers also have a separate external circulating pump.

System Boiler

System boilers work by heating a central-heating system directly, producing hot water in a cylinder. A system boiler, like a regular boiler, works by storing hot water. However, system boilers have some important differences from regular boilers. First, many major components of the heating system are built in, meaning installing a system boiler is quicker, and therefore less expensive than a conventional boiler. Secondly, the system boiler pumps hot water to the radiators and hot-water cylinder, producing a faster response with more economical operating costs.

Combi Boiler

A combi, short for combination, boiler is a clever space-saving idea and becoming an increasingly popular option in Bristish homes. In fact, combis currently account for the majority of all new domestic boilers installed in Great Britain. Combi boilers don’t have a separate hot water cylinder, making the unit more compact. Other benefit of combi boilers is the hot water is delivered at mains pressure. Combi boilers also require less pipe work with shorter installation time, saving you money.

Boiler Efficiency

Boiler efficiency is measured by fuel-utilization efficiency. This measures how efficient the boiler is at converting the energy it uses into heat for your home over a 12-month period.

ErP Directive

In October of 2009 the EU adopted a new framework for the efficiency of energy-related products, named the ErP Directive. It is hoped that improving the efficiency of energy-related products across the EU will help reduce environmental impact while leading to cost savings for consumers. The ErP Directive seeks to phase out poorly performing energy-related products, including boilers, with an ultimate goal of:

● Reducing EU greenhouse gas emissions by 20 percent

● Improving overall energy efficiency by 20 percent

● Increase the share of EU energy consumption produced from renewable resources by 20 percent

From September 2015 the ErP Directive applies to both residential and commercial-heating products throughout the EU, including boilers. All boilers, and other heating products, are awarded an efficiency rating that must be clearly displayed on each product.


SEDBUK, the Seasonal Efficiency of Domestic Boilers for the UK, rating was developed in cooperation with the government and manufacturers to give a fair comparison of side-by-side boiler efficiency. The SEDBUK model was designed to be a more accurate method of measuring efficiency over just laboratory testing alone. This involves comparing theoretical data from boiler tests against field trials in 99 homes over a period of three years. A clear rating system now applies to all boilers, with designations from A to G, with A being the most efficient.

How to Choose a Boiler

Before deciding on what type of boiler will be best suited to the needs of a particular residence, homeowners should seek professional guidance. Whilst a Baxi combi boiler has become increasingly popular with homeowners, it is best to get a through in-home evaluation from a licensed professional before making a decision.