Boilers: How we test
Each of the boilers we've tested has been carefully monitored to record its gas and electricity consumption, efficiency and emissions, as well as being evaluated by a Corgi registered gas installer on how easy it is to install, service and use in the home.
Efficiency
Our lab technicians take multiple measurements
We conducted tests according to European Standards to measure how much of the gas each boiler burns is converted into heat.
One of the strange quirks of condensing boilers is that while in condensing mode, they can be more than 100% efficient – they achieve this because as well as using heat from the fuel they're burning at the time, they also reclaim heat from the flue gases to heat your water too.
In theory a condensing boiler can have a maximum efficiency of 107%, providing it uses all the heat from the fuel and the flue gases to heat your water. In practice most of the boilers we tested don't reach this level.
Ease of use
Our installer gets to grips with this boiler's interior
Our gas fitter installed each appliance, checking the gas and electrical connections were easy to make and had plenty of room.
Each boiler was assessed for how straightforward it was to install and service, and how easy it was to replace common spare parts, as well as the noise it produced, the warranty provided and the ease of using the controls.
Durability
Boilers are expected to last for a long time. We ran a limited durability trial that involved turning the boilers on, running them for 5 minutes at full capacity and switching them off again.
We did this 2,920 times – the equivalent of using a boiler for almost a year (although combis will be fired up much more frequently). Most of the boilers made it through unscathed, but the temperature display on 2 models both developed a minor fault after 300 cycles.
The casings of 2 of the boilers were showing signs of wear and tear after the durability trial too.