The article explores how having both emission taxes and emissions trading in place at the same time can lead to inefficient outcomes in reducing carbon emissions for businesses in the European energy sector. The study finds that firms in the EU Emissions Trading Scheme that also face domestic energy or carbon taxes might end up spending more money on emission reductions than necessary, while some companies benefit from lower international emission permit prices. Contrary to belief, adding national emission taxes on top of the current system doesn't necessarily fix this. The researchers suggest that firms subject to both emissions trading and carbon taxes should be exempt from the latter, as it might not help the environment and can actually end up subsidizing certain companies instead. This could save money overall and still comply with EU regulations.