We quantify the energy radiated through all the collisional lines in a photoionized nebula in the presence of temperature fluctuations in the form of hot spots caused by an unknown heating process. The excess energy radiated in the lines as a result of the fluctuations is found to scale linearly with their mean-square amplitude t2. We find that the combined mechanical luminosity of stellar winds, champagne flows and photoevaporation flows from proplyds is insufficient to account for the temperature fluctuations of typical HII regions, but that stellar winds may possibly explain the fluctuations in planetary nebulae.