Scaling up a quantum processor to tackle real-world problems requires qubit numbers in the millions. Scalable semiconductor-based architectures have been proposed, many of them relying on integrated control instead of room-temperature electronics. Therefore, tight integration of the qubit chip with ultra-low power CMOS electronics presents a promising route. We demonstrate DC biasing qubit electrodes using a custom-designed 65nm CMOS capacitive digital-to-analog converter (DAC) operating on the mixing chamber of a dilution refrigerator below 45 mK. Our results validate the potential of very low power qubit biasing using integrated circuits whose connectivity requirements do not increase with the number of qubits.