Waste-to-energy (WtE) plants are traditionally designed for clean and economical disposal of waste. Design for output on the other hand was the guideline when projecting the HRC (HoogRendement Centrale) block of Afval Energie Bedrijf Amsterdam. Since commissioning of the plant in 2007, operation has continuously improved. In December 2010, the block's running average subsidy efficiency for one year exceeded 30% for the first time. The plant can increase its efficiency even further by raising the steam temperature to 480°C. In addition, the plant throughput can be increased by 10% to reduce the total cost of ownership. In order to take these steps, good preparation is required in areas such as change in heat transfer in the boiler and the resulting higher temperature upstream of the super heaters. A solution was found in the form of combining measured data with a computational fluid dynamics (CFD) model. Suction and acoustic pyrometers are used to obtain a clear picture of the temperature distribution in the first boiler pass. With the help of the CFD model, the change in heat transfer and vertical temperature distribution was predicted. For the increased load, the temperature is increased by 100°C; this implies a higher heat transfer in the first and second boiler passes. Even though the new block was designed beyond state-of-the art in waste-to-energy technology, margins remain for pushing energy efficiency and economy even further.