A wireless battery-powered daylight sensor for measuring a total light intensity in a space, the sensor comprising: a photosensitive circuit operable to generate a light intensity control signal in response to a measured total light intensity; a wireless transmitter for transmitting wireless signals; a controller coupled to the photosensitive circuit and the wireless transmitter, the controller operable to periodically sample the light intensity control signal and transmit wireless signals in response to the light intensity control signal, the controller operable to store sampled light intensity values in a memory and to analyze the sampled light intensity values to determine the amount of change of the measured total light intensity; and a battery for powering the photosensitive circuit, the wireless transmitter, and the controller; wherein the controller is operable to transmit wireless signals using a variable transmission rate that is dependent upon an amount of change of the measured total light intensity; and wherein the controller is further operable to sample the light intensity control signal to generate at least one first sampled light intensity value; store the at least one first sampled light intensity value; determine at least one first predicted light intensity value using an estimator based on a previous measured light intensity value; calculate the amount of change of the measured total light intensity as the error between the at least one first sampled light intensity value and the at least one first predicted light intensity value; if the error is less than a predetermined value, sample the light intensity control signal to generate at least one second sampled light intensity value; and if the error equals or exceeds the predetermined value, calculate a new estimator for subsequent use, and transmit a digital message representative of the at least one first sampled light intensity value. a photosensitive circuit operable to generate a light intensity control signal in response to a measured total light intensity; a wireless transmitter for transmitting wireless signals; a controller coupled to the photosensitive circuit and the wireless transmitter, the controller operable to periodically sample the light intensity control signal and transmit wireless signals in response to the light intensity control signal, the controller operable to store sampled light intensity values in a memory and to analyze the sampled light intensity values to determine the amount of change of the measured total light intensity; and a battery for powering the photosensitive circuit, the wireless transmitter, and the controller; wherein the controller is operable to transmit wireless signals using a variable transmission rate that is dependent upon an amount of change of the measured total light intensity; and wherein the controller is further operable to sample the light intensity control signal to generate at least one first sampled light intensity value; store the at least one first sampled light intensity value; determine at least one first predicted light intensity value using an estimator based on a previous measured light intensity value; calculate the amount of change of the measured total light intensity as the error between the at least one first sampled light intensity value and the at least one first predicted light intensity value; if the error is less than a predetermined value, sample the light intensity control signal to generate at least one second sampled light intensity value; and if the error equals or exceeds the predetermined value, calculate a new estimator for subsequent use, and transmit a digital message representative of the at least one first sampled light intensity value.