In indoor environments, the thermal environment, particularly the air temperature, is crucial for occupant comfort and energy consumption. In contrast, advanced computer simulations have emerged to accurately predict temperature variations and energy use in indoor spaces in recent decades. Simple hand calculation methods are still needed to provide initial estimates for architecture or facility managers. However, more reliable methods must be used to estimate the relationship between temperature and energy consumption in daily-used small spaces, such as bathrooms. Despite lower overall energy consumption compared to larger spaces, bathrooms often have higher energy consumption per unit area, indicating significant potential for energy savings. This study aimed to correlate temperature changes and energy consumption using data collected in a laboratory chamber. The chamber dimensions and layout were designed to represent a typical bathroom, facilitating a toilet, showerhead, basin, ceiling light, portable heater, and exhaust fan. Eight scenarios with different combinations of lighting (on/off), heater (on/off), and exhaust fan (on/off) settings were tested, with each scenario repeated twice for a total of 16 sample cases. Building on the power-law relationships between temperature rise, energy release rate, and wall heat gain established by previous researchers, this study updated the coefficients of the original equations to fit better the experimental data collected. The correlation model developed in this study can be used to predict bathroom temperatures based on environmental settings or to estimate energy consumption based on desired temperature. The model provides a simple yet effective tool for building designers and facility managers to assess bathrooms' thermal performance and energy implications during the design phase or for retrofit applications. The results of this study could directly inform more sustainable design strategies for bathrooms. However, it should be noted that the current study is the beginning that only considered two heat sources (i.e., heater and lighting). Future research should investigate the impact of additional factors, such as hot water flow, on bathroom temperature changes and energy use during showering to identify a thermal comfort and energy-saving bathroom environment.