A one-year field study compared the conventional 250W IR heat lamp with an energy-efficient 175W radiant heat lamp for swine farrowing operations. The results indicate that the energy-efficient heat lamp showed a 36 annual cash savings per heat lamp (@ 0.10/kWh); a 1.2% absolute reduction in birth-to-wean piglet mortality (5.0% vs. 6.2%); a 45% lower lamp failure rate (18% vs. 32%); and a slightly higher piglet rate of gain (217 g/day vs. 211 g/day);Investigation of a discrete-sampling, photographic method indicated that a sampling interval of up to 60 minutes would be adequate for photographic recording of the piglet heat lamp use (HLU) behavior. The electronic load cell device developed for measurement of HLU behavior of piglets could accurately and automatically record the number of piglets utilizing the heat lamp for the entire trial period, but it could not determine the lying patterns of the piglets;Dynamic HLU of piglets exposed to 250W, 175W, or 125W heat lamps was measured during four production seasons. The results indicated that there was a consistent circadian pattern in HLU for all the heat lamps tested. HLU was significantly higher during the day than at night. The dynamic HLU behavior was greatly affected by the heat lamp size. The 175W heat lamp produces the best piglet resting pattern. The thermal needs of neonatal piglets declines with increasing age;The effects of the lamp output and color on piglet behavior and performance were evaluated at two air temperatures of 18 (±1.5)°C and 27 (±1.5)°C, respectively. The results indicate that the variable-output lamp is more suitable for swine farrowing operation. Compared with the constant-output lamp, the variable-output lamp would yield an annual energy savings of 29 (@ 0.10/kWh and 88% of usage). The red-color rays showed no advantages over the clear rays with regards to piglet behavior and performance. The ambient temperature in farrowing unit significantly affects heat lamp usage of the piglets;A mathematical model describing the thermal interactions between the environment and piglets was developed. The model predictions indicated that the heat lamp need of piglets was affected by the piglet age and ambient temperature, and the ambient temperature was the most important factor affected the heat lamp needs of piglets. The heat lamp needs of piglets was gradually decreasing with age and the average decreasing of heat lamp needs of piglets was 1 W per day, the decreasing of heat lamp needs of piglets was sharp as 10.5 W/°C with ambient temperature. Compared with the results of previous experiment, the mathematical results appeared to be a reasonable approach for assessing the heat lamp output at different piglet age under various environmental conditions.