Bringing environmentally sustainable practices to low-income communities is important for a variety of reasons. As shown, renewable energy yields monthly monetary savings in energy costs, which will ultimately reduce the amount individuals will have to spend on their energy bills. Additionally, the residential sector contributes to a significant portion of St. Louis’s emissions. Reducing grid-dependence through renewable energy will help to reduce annual emissions. Finally, making environmentally friendly technologies more accessible across income levels makes the issue of climate change more inclusive.

The work outlined in this report analyzes the costs and savings of small solar arrays, but more possibilities exist to extend the breadth of this analysis. For future ESE students wishing to partner with a community organization and independently research renewable energy, possible projects are outlined below.

Habitat STL Site Selection and House Design

In light of the analysis of current and future costs, the next step for this project would be an actual design and proposal for a new or existing Habitat home. Using energy consumption data of a Habitat home and solar resource data in St. Louis would lay the foundation for a feasible proposal that adds solar to small single-family homes.

The MATLAB simulation from this report can be altered to show results for different levels of energy consumption. Based on annual usage of existing Habitat homes throughout the St. Louis region and structural factors (i.e. shading, roof tilt), the ideal location and array size can be chosen. Due to additional environmental factors that may be identified, this could turn into a more complicated optimization problem than what is detailed in this report. Accounting for more variables yields more accurate simulation results.

Alternatively, if Habitat wishes to consider solar arrays for future builds, a proposal or design could be generated that details the ideal location, orientation, and solar array for a new home. This would require close contact with the Habitat building team to ensure all proposed additions met Habitat’s specifications.

Incorporating Battery Storage or a Microgrid System

The model built in this report focuses solely on grid-connected PV systems. If a carbon tax does indeed come to fruition, it could be more economical to build isolated systems that incorporate battery storage or operate as a microgrid. This would undoubtedly add expense, but using cost projections of both utility power and storage options, the cost and emissions analysis could calculate the payback period and levelized cost of additional PV system features.

Technologies such as the Tesla Powerwall[i] and Solar Roof[ii] are currently too expensive to justify implementing in Habitat homes, but these are examples of system elements that could sustain a home on purely solar energy. For states like Missouri that have a poor net-metering policy, storage options help residents take full advantage of the energy they produce and make homes more resilient to utility-scale outages.

Most grid-connected solar systems stop producing during outages to prevent back feed that is dangerous to utility workers interacting with powered lines. It is possible to use special inverters[iii] or battery backup to isolate the system when the grid goes down. This allows solar arrays to continue producing and charging the storage unit so loads can continue to be powered during a utility outage.

Cost analysis and projections offer one lens through which to explore storage and microgrids, but this is also a very technical element that could be explored. Understanding the actual operation and interconnections of a microgrid requires knowledge of power systems, photovoltaic behavior, and battery operation and degradation over time.

Net-Zero Homes and Communities in St. Louis

Net-zero energy facilities are gaining popularity because they produce as much energy as they consume over the course of a year. They can still be grid-connected, so long as they send as much energy back to the grid during overproduction as they pull from it. While Missouri’s net metering policy does not necessarily reward overproduction as well as it could, net-zero is very attractive from an emissions point of view.

Since Habitat homes represent a small fraction of low-income housing in St. Louis, this idea could be scaled from single-family homes, multi-family apartment complexes, and larger commercial operations.

Energy Efficiency in Habitat STL Homes

Habitat STL builds its facilities with the intention of using energy efficient appliances and materials. The sustainable design saves homeowners lots on utility bills, but there are always opportunities for more energy efficiency retrofits. When looking to make a facility net-zero, energy efficient upgrades is often the first place to look, as these are usually less expensive than adding more solar capacity.

For students interested in building design and energy efficiency, comparing various possible appliances and house designs would be a possible project that could greatly reduce consumption of a home. As mentioned earlier, there are many passive ways to save energy. Newly built homes are a great opportunity to make energy efficient changes to structure, while cost and payback analysis on appliances may reveal new or better technologies that Habitat could implement in their builds.

This potential project would have both a technical and financial component. Energy conservation opportunities are often detailed in retrocomissioning reports with implementation cost, savings, and payback period displayed for the customer.

Analysis of Different Financial Models

As mentioned, the simulation results of this report assume the system was financed using the simple cash purchase model (see section 3.1). Seeing as up front cost is a major barrier preventing Habitat from implementing solar on their homes, a useful tool could be cost analysis using different financing mechanisms discussed in section 3 of the report.

It can be difficult to convince stakeholders to pay to incorporate energy efficiency measures. A proposal to finance solar that minimizes up front cost and maximizes benefits for the homeowner could be effective at highlighting the benefits of different solar financing options.





[iii] “Does solar work in a blackout?” Third Sun Solar, May 29, 2013. Retrieved from