Actually this may be enough for modern IoT sensors, adding capacitor and doing transmission less often helps. Even flashing the LED (5mA pulses for 1ms) is only

Actually this may be enough for modern IoT sensors, adding capacitor and doing transmission less often helps. Even flashing the LED (5mA pulses for 1ms) is only 5uA on average (once a second, 0.1% duty cycle) or even 1uA (once a 5 second, 0.02% duty cycle).