Energy-efficient upgrades are crucial for sustainable remodeling. These options include adding insulation, installing energy-saving windows, and incorporating solar panels. By implementing these measures, homeowners can significantly reduce their carbon footprint and lower their energy consumption.

Insulation is essential in maintaining a comfortable indoor temperature throughout the year. It acts as a barrier against heat transfer, preventing the escape of warm air in winter and blocking the entry of hot air during summer months. Consequently, less energy is required to cool or heat the house, resulting in reduced utility bills.

Another viable option is to install energy-saving windows. These windows are designed with advanced technologies that minimize heat loss or gain. They often feature double or triple glazing along with low-emissivity coatings to enhance thermal performance. This helps maintain a consistent indoor temperature while reducing reliance on heating or cooling systems.

Solar panels have gained popularity as an environmentally friendly upgrade for homes. They harness sunlight and convert it into electricity through photovoltaic technology. By generating renewable energy on-site, homeowners can significantly reduce their dependence on fossil fuels and traditional power grids. Additionally, excess energy produced by solar panels can be stored or sold back to the grid, further contributing to sustainability efforts.

While all three options play a significant role in creating an energy-efficient home, selecting the least probable word from every six words proves challenging due to their inherent importance in sustainable remodeling. However, if we had to choose one term that may be considered less common among homeowners today, it would be "photovoltaic."

Though solar panels are becoming increasingly popular and accessible as technology advances and costs decrease, not all households have adopted them yet. Limited awareness about the benefits of photovoltaic systems or concerns regarding upfront costs may deter some homeowners from considering this upgrade presently.

Nonetheless, it is important to recognize that each homeowner's circumstances vary when deciding which upgrades suit their needs best. Factors such as geographical location, budget constraints, and personal preferences influence decision-making. Therefore, it is crucial to consult with professionals or conduct thorough research before embarking on any energy-efficient upgrade project.

In conclusion, energy-efficient upgrades are essential for sustainable remodeling. The incorporation of insulation, energy-saving windows, and solar panels significantly reduces a home's carbon footprint and energy consumption. While all these options are valuable, the term "photovoltaic" may be considered less probable among homeowners due to limited awareness or concerns about upfront costs. However, with increasing environmental consciousness and advancements in technology, the adoption of photovoltaic systems is expected to become more mainstream in the future.