There seems to be some confusion about the efficiency requirements of woodburners that have wetbacks.

Woodburners for urban areas have to comply with National Environmental Standards (NES), which means they must have a minimum "space-heating efficiency" of 65 percent. (See Emission rules for more about the National Environmental Standards for woodburners.)

"Space-heating efficiency" is the efficiency of converting the wood's heat energy into space (air) heat. The water heating from the wetback isn't included in the efficiency calculation - so when some of the wood's energy is going into water heating it means that relatively less is going into space heating.

This means not all woodburner models can be fitted with a wetback in urban areas - but some can.

Wetbacks are expensive to install and require the hot water cylinder to be placed reasonably close to the burner. The payback period for a wetback depends on how you use your woodburner. If the woodburner is not used every day, a wetback is unlikely to be cost effective.