Installing a condensing or high efficiency boiler is one of the most significant energy saving measures. Most properties that have been converted or newly built in the last 5 years or so will already have a condensing boiler, but for those with older properties it is worth checking and if necessary considering replacing your boiler. These new high efficiency boilers are available as gas, oil and LPG fired variants and depending on the size of your property (and the number of radiators you have) will cost from around £1,000 plus installation.
Condensing boilers can operate at around 90% seasonal efficiency, whereas older boilers typically operated in a range between 55%-65%. This efficiency gain will significantly reduce energy consumption and associated greenhouse gas emission and can translate into annual savings for the average detached property of up to £200 every year. Based on typical installation costs these would indicate a payback period of between 6 -7 years, but with rising fuel prices this period is likely to shorten considerably. Adding a new high efficiency or condensing boiler is also likely to add at least an amount equivalent to its cost to the value of your property.
How do condensing or high efficiency boilers work? If you've ever stood next to the flue of a traditional boiler, you can't have failed to notice the hot exhaust gases that are pumped out when the boiler is operating. Condenser boilers harness this heat energy using a heat exchanger to pre-heat water in the boiler. When the condenser boiler is working at maximum efficiency (around 90% compared to the 65% of older non-condensing boilers), the temperature of flue gases is reduced to a level where they are condensed out to water vapour - hence the name condensing boiler. This water tends to be acidic so needs to be piped away to a drain or soakaway - hence installation costs are usually a little higher.
Sizing & installation: Your old boiler will probably having an output rating measured in Btu's (British Thermal Units) whereas all new boilers are now rated in kilowatts (kw). The following formula is used for conversion:
1 BTU = 0.00029 kWh
Historically heating engineers would tend to over-estimated heating requirements in a 'belt & braces' approach, which meant that most of the time efficiency was even lower than the quoted figures , as they were running at part load. As result it is probable that you will need a smaller boiler than previously installed, particularly if you have fitted additional insulation to your property.
We strongly recommend seeking professional advice from a CORGI or OFTEC registered installer before choosing an appropriate replacement boiler.
Further information on high efficiency or condensing boilers, including a boiler efficiency database can be found by following this link.