Household boilers are a major investment, perhaps not as glamorous as the house itself, or a car, but the average boiler lasts 10-15 years, more than double the length of time that most people keep their vehicle, so a buying decision for this household asset is one of the most important you'll make. Especially when you consider that over 80% of home energy is consumed by running the central heating and creating hot water.

Most industry experts recommend that old, inefficient boilers are replaced as soon as household finances allow. Older boilers tend to be the most inefficient, with the turning point in efficiency widely recognised as being the mid-1990s. Boilers manufactured before that date generally operate at an efficiency rate of 30-40% below the high efficiency modern condensing boilers.

You'll be pleased to hear that the chances are if you've had a boiler fitted in the last five years, then you've probably got one of these condensing boilers. However, even within this boiler type there are more and less efficient models. The best way to determine whether you're getting the best boiler for your money, is by checking their energy efficiency grade, with A-grade boilers offering over 90% efficiency.

Energy efficiency is measured in two respects. Firstly, by the efficiency with which the boiler transfers condensed water back to heat. Secondly, by the heating controls fitted with the boiler, that is the thermostat, heating timer, radiator control valves and hot water thermostat. The installation of even a basic minimum set of heating controls will save 20% energy compared to a 'wet system' where the boiler has no controls, as it enables you to take greater control of your system. Likewise an average reduction of around 1C over the year can save 10% in costs. For advice on boiler efficiency, just look out for badges from organisations such as the Energy Saving Trust, who give recommended boilers their stamp of approval.

Once you've selected your boiler of course, you've got to make sure you maintain it effectively. The best method of boiler maintenance is comprehensive and systematic, preventing and anticipating problems. Without this kind of preemptive boiler maintenance, you're only going to be reacting to major malfunctions, and such unplanned work – repairs, call-outs, and parts – can obviously be very costly.

Regular boiler maintenance basically gives you extra insurance against disastrous breakdowns, enabling you to recognise problems in advance, rather than wasting time and money trying to evaluate failures when they've become more serious down the line. Likewise, an effectively maintained boiler is always going to operate at a more efficient level, burning less fuel to create the same amount of energy.

Of course, much boiler maintenance must be carried out by a qualified plumber, but there are some simple checks that you can carry out at home without qualified supervision, and which are still essential to maintaining a proper functioning boiler. The most important of these checks is of the boiler system pressure. Check your manual for the optimum pressure range of your boiler when it's switched off and been allowed to cool to room temperature (for most standard household models, it's usually between 1 and 1.5 bar).

If the pressure is too low then it will need 'topping-up'. Using your boiler's operating manual, you can open the filling valve to allow more water into the system and so increase pressure. Having to do this on a regular basis may indicate a leak in the system, and then the boiler installer or other qualified engineer should be notified.

Similarly, depending on your boiler model, you may be able to carry out a manual boiler reset in the event of a system error. Most modern boilers, with digital displays, will show if there is a problem. This display normally takes the form of a code, each code corresponding to a particular fault. Some codes call for an engineer to be called, others can be solved by a simple reset. Again, follow the user guide, but this action is really very like the 'power-off' operation everyone has used, at one time or another, for their home PC or laptop! But resets should, of course, not be a substitute for proper boiler maintenance carried out by qualified professionals.

The user guide to most boilers will recommend at least an annual service, if not more regular boiler maintenance. To find out how British Gas can help you with this, head to: www.britishgas.co.uk/homecare