Effect of grid feed-in curtailment of a PV system with heat or electricity storage (battery) is simulated as a function of system dimensioning with a focus on the induced PV power losses (due to this limit) and on cost balance. Heat storage is provided by a domestic hot water tank heated with heat pump or electrical water heating system. The case studied is based on a Swiss household with an annual electricity energy consumption of about 5000 kWh (without thermal loads). The effect of electricity generation forecast imprecision on cost balance optimization is also evaluated. The simulations showed that only relatively small electrical storage capacities or controllable thermal loads are sufficient to reduce considerably the PV-losses. Forecast inaccuracies have a non-negligible detrimental impact on cost balance with the designed algorithm.