Assessment of quarterly and annual carbon savings in historic buildings from on-site energy production

This study assesses long-term quarterly and annual carbon savings at a historic religious site by measuring monthly and yearly savings from on-site energy generation, consumption, and storage from 2016 to 2021. The case study building features Mid-Century Modern architecture and supports religious activities, communal offices, and educational and recreational uses. The development was completed in the 1960s. It is located in the northeastern United States and is considered one of the state’s historic buildings. Its main on-site energy source is photovoltaic (PV) power, with an annual capacity of over 35,000 W. The estimated U -values for building components range from 1.80 to 3.00 W/m 2 K. Based on the kgCO 2 e/kWh benchmark for solar panels, total annual carbon savings from the development ranged from −0.460 to 3.640 tonnes. Quarterly carbon savings ranged from 0.910 tonnes in the fourth quarter of 2020 to 3.120 tonnes in the second quarter of the same year. Over the years, the second and third quarters have consistently shown the highest quarterly carbon savings, with July having the highest monthly savings. Between 2017 and 2020, the average annual carbon savings were estimated at 1.030 tonnes, with the average yearly cost per kWh remaining below 1 US dollar. The research shows that historic developments can be sustainable if suitable retrofit strategies or interventions are applied during their operations. For instance, in 2020, about 42% of annual energy savings contributed to carbon reduction, resulting in carbon savings equivalent to 58% of total annual energy consumption. The findings can inspire historic building owners to consider affordable strategies to improve performance. The investigation further strengthens the need for consistent, periodic building energy assessments to improve energy efficiency and overall building performance across different seasons.