Boxing Day sales are underway, but shoppers are being warned to research before buying

Consumer New Zealand's been testing a number of products ahead of the sales, and found top dollar or promotional pricing doesn't always mean good quality.

One example is a 2-thousand 6-hundred dollar espresso machine, which earned the 'Don't Buy' badge.

Consumer New Zealand Head of Test Paul Smith says its up to the consumer to research, so they get what they need.

Smith says sale products are often things that don't work so well, as opposed to the best selling, highest performing items.