In this paper we discuss the differences between the industrial and academic definition of smart-grid readiness of heat pumps and investigate possibilities to bridge this gap such that existing heat pumps, to a higher degree, can participate in a smart-grid or flexibility setting. A weather compensated heat pump has been equipped to enable heating reference tracking by overriding the outdoor air temperature measurement. The reference tracking has been performed using a model predictive controller and a PI-controller. The results show that it is possible to track a heating reference but also that operating the heat pump according to smart-grid objectives has consequences, such as reduced COP and increased defrosting rate. The model predictive and PI-controller showed little difference in performance, meaning that even simple rule-based controllers can be used for tracking. Lastly, the paper provides suggestions for signals that should be available if heat pumps in the future should operate closer to the researchers' expectations of smart-grid readiness.