The residential sector is a substantial consumer of energy in Spain. A new electricity tariff was applied in Spain to make home consumers manage their energy consumption based on the variation of electricity price during the day, which contributes to energy security, increases the penetration of Renewable Energy Sources (RES) into the grid, maintains grid stability, and reduce CO2 emissions. To ensure the successful implementation of the new Demand Response (DR) program, it is necessary to investigate the factors that might affect home energy consumers to use the Home Energy Management System (HEMS). This work aims to examine the factors that affect the Spanish home energy consumers' acceptance to participate in DR, which have not been studied yet after the new electricity tariff. In addition, highlighting the role of economic benefits and environmental awareness factors in the acceptance of participating in DR using HEMS. The Technology Acceptance Model (TAM) is used in this work with four independent factors, attitude toward use as a mediating effect, and one dependent variable of intention to use, then hypotheses were set for each. The selected research method was a diagnostic survey technique through a standardized survey questionnaire distributed in person and online, that Galicia, Northwest Spain was taken as a case study. In terms of the statistical results of Probability value (P-value) and Critical Ratio (C.R.), it was found that the family's economic benefits and environmental awareness affect the attitude toward using HEMS after the new electricity tariff in Spain and attitude toward using HEMS has a significant impact on the intention to use HEMS. However, the usefulness and ease of using HEMS for managing energy consumption do not influence the consumers' attitudes toward adopting HEMS. The direct effect of usefulness on the intention of using HEMS is higher than the indirect effect through attitude. Thus, the mediating effect of the attitude to the relationships between usefulness and intention to use is not significant. The results help the Spanish policymakers to draw up policies to effectively disseminate strategies to encourage home consumers to contribute to energy security and assist energy management researchers in incorporating key factors that impact energy consumers into their proposed models. By doing so, these models can clarify the financial and environmental advantages of effective energy consumption management, thereby encouraging energy consumers to adopt more sustainable practices.