The overarching aim of the study is to identify how greenhouse gas emissions can be reduced in the Massachusetts residential sector, particularly through the adoption of renewable energy systems (RES) discussed in the previous section. This section reviews similar studies that have demonstrated the impact of the highlighted renewable technologies on greenhouse emissions. To begin with, Kelly et al. (2016) investigated the potential of air source heat pumps (ASHPs) as a replacement of solid and liquid fossil fuels in the Irish residential sector. By employing economic, scenario, and sensitivity analysis; the researchers reported that utilizing the ASHPs as an alternative for the fossil fuels, not only led to higher cost savings, but also reduced emissions and overall improved health benefits. The analysis showed that up-to 8kt of particulate matter, 3.7kt of nitrous oxides, and 4.3 million tonnes of carbon dioxide could be eliminated by using ASHPs.
In a separate study, Szekeres and Jeswiet (2018) utilized average hourly data for electricity generation and hourly outside temperature for each month in the year to estimate the emission of greenhouse gases when heat pumps were both used and not used. Simulation software was also used to determine the heating needs of single dwellings that were detached. Findings obtained showed that using heat pumps in residential areas could lead to a reduction in the emission of greenhouse gases of between 15% -to- 18% in January. Likewise, it would also lead to reduced energy consumption between 12% and 68%, and lower costs of operation than in electric or oil heating. Litjens et al. (2018) further developed an assessment model based on techno-economic and environmental aspects to quantify the influence of photo-voltaic combined with ground source heat pumps (GSHPs) in 16 residential buildings in the Netherlands. Results from the analysis showed that using GSHPs with PVs led to a reduction of carbon dioxide emissions of 73t CO2-eq, which was equivalent to an 80% reduction over 30 years.