Paul Massara said the actual unit prices of gas and electricity in the UK are among the lowest in Europe, but bills were high "because British houses waste so much energy".
In the supplier's second "Energy Explained" report, Mr Massara said: "If we can increase the efficiency of the UK's old and draughty housing, we can ensure that annual energy bills are some of the lowest too."
The npower chief executive warned consumers that the cost of bills was set to increase unless households introduce efficiency measures.
More top news
Sun glasses and brollies at the ready this weekend
A new official photograph of a beaming Prince George has been released to mark his fourth birthday.
Downton Abbey has inspired a butler boom in China where many people now consider having a butler to be the ultimate status symbol.