On the global carbon market, credits for distributing efficient cookstoves in countries that traditionally burn wood or kerosene are the fastest growing type of offset traded. A new study evaluates these credits against published data on cookstove efficiency and usage and concludes that cookstove offsets are 10 times overvalued. The group offers guidance for choosing carbon offsets from cookstoves projects that reduce greenhouse gas emissions and the impact on health, and for revising offset programs to avoid excess crediting.