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A puffer represents a sort of "back-up" or "reserve" of hot water that can be used when and how you wish, both for heating and for domestic hot water. It is a big steel cylinder, covered with a thick insulating shell, within which the water is stored.

They come in different sizes, depending on the requirements, that can go from 200 to over 2000 litres.

The disadvantages are that you must have the available space (a boiler room or a garage are ideal, bear in mind that an average 650 litre puffer measures h.1.73 x 95 cm in diameter) and of course a slightly higher budget, while otherwise the puffer only features positive aspects.

Why is it useful?

In the event of heating only, the puffer stores the excess hot water produced by the stove and releases it in the radiators when necessary. With the - extremely cost-effective - result of having heating that works even when the stove is switched off!

In the case of heating and domestic hot water production also, there is always a large available amount of hot water produced by the stove, instantaneously and whenever you want, even when the stove is switched off.

When is it necessary or strongly recommended

• When there are solar panels: the hot water produced must be stored somewhere, to use it when it is required.
• In the stove/underfloor heating system combination: if you have an underfloor heating system to be powered with the stove, instead of radiators, a puffer is practically mandatory. The water produced by the stove reaches 70-80°C, a temperature that is fine for radiators, but not for the underfloor heating system, which does not exceed 30°C. Without the puffer, the excess energy would be lost to cool the water, while with the puffer it is simply stored and mixed with cold water until reaching the required temperature. 

What size should you choose?

It depends on what it is used for, in addition to the space available. In general, a puffer should have a minimum capacity of 20 litres x kW in the case of a pellet-burning product, 30-35 litres x kW in the case of a wood-burning product.