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
Phil Rudd also pleaded guilty to possessing crystal meth and marijuana in a New Zealand court.
Ed Miliband will order an emergency recruitment drive of nurses so an extra 20,000 will be working in the NHS by 2020.
Sir John will give a speech later today saying a Labour-SNP government would be "weak and unstable" and wreck Britain's economic recovery.