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Religious Congregations and Zero Net Energy

May 16, 2022 by Mark Hanson

A zero net energy building is a facility where all the energy that is required for operation for a year is provided by an on-site renewable energy system. In fact, the building could even take this further by producing energy beyond the total of its annual needs to share with others. The ongoing progress of renewable energy technology has made on-site solar PV (photovoltaic) renewable energy the easiest to install and cheapest energy system for the last decade or so.

The first question that perhaps comes to mind is how does a convent or any building obtain energy after the sun sets, or on a very dark cloudy day where some solar power is being produced, but much less than on a clear day. This is where the term “net” enters the conversation. By far the most common arrangement is for the building to be connected to the electrical grid. The PV system is then sized to provide a total amount of energy over a year to match (or exceed) what a building uses. When there is more energy produced than is needed at any moment, the excess is exported (sold) to the grid. When there is not enough energy at any moment, just enough energy is imported from the grid to meet the building demand beyond what the solar PV is producing.

To make things even more interesting, battery energy storage systems (BESS) are now being included so that some of the energy that would be exported to the grid is stored for later use, especially during electric demand peaks (which are typically priced according to how high the peaks are). BESS may also be used for emergency power back-up. The costs of BESS have been dropping rapidly.

If the building uses only electricity, then providing zero net energy with on-site solar results in no carbon emissions, again on a net basis. An all-electric building will heat and cool with heat pumps either exchanging heat with the ground (commonly called a ground-sourced heat pump or geothermal system) or with the outside air (called and air-sourced heat pump). As we rapidly move away from natural gas energy for heating to avoid CO2 and methane emissions—which are associated with climate change—heat pump systems are becoming common in new construction and remodeling.

Caring for the Earth is essential. The goal of a net zero energy building that costs no more to build and operate than a conventional design over say a 30-year time horizon is the financial goal to make this all doable in a world of financial constraints.

Two Congregations Implementing Net Zero Energy

Hoffman has worked with many congregations and other types of clients that have implemented efficiency and, in many cases, solar PV energy systems. We are currently working with two congregations that are pursuing net zero energy for large portions of their campuses. Their stories are inspiring.

The Dominican Sisters of San Rafael (Marin County California) are planning a remodel and addition to Dominican Convent, one of their convent buildings. The old natural gas heating system is being removed and the heating and cooling for the existing building plus addition (22,000 square feet) will be air sourced heat pumps. They will also move to an air-sourced heat pump water heater and induction stove top for sister use. Gas usage will be henceforth limited to only the main prep kitchen equipment. A solar PV system will be installed on the roof of Dominican Convent as well as on some carports. The carports include two electric vehicle charging stations. BESS are part of the plan to store energy to provide power during peak period (4 pm to 9 pm) when electric rates currently are over 50 cents per kWh and to provide emergency back-up power which have been common recently due to wild land fires in recent years. Further emergency back-up will be provided by a small kerosene generator that will be rarely required to operate.

So, what is the up-front cost for the solar PV (roof and carport); BESS; microgrid; and emergency generator? After using available incentives, the Congregation has no up-front cost. The Congregation is using third-party investors. The latest estimates of the annual cost (fixed for 20 or 30 years when they’ll own the system) is that it will be the same as what the energy costs for a conventional building would have been. The financial difference is that the Congregation’s bill will not change (whereas utility rates in California are forecast to grow about 7% or more annually in the coming years).

The Benedictine Women of Madison at Holy Wisdom Monastery (Middleton, Wisconsin) have a similar vision in bringing their two main buildings (Holy Wisdom Monastery and the Retreat and Guest House) to net zero energy. As the Monastery is already a geothermal building (some solar installed when the building was completed in 2009 and more added in 2014), the next step in their journey is to convert their 1950’s Retreat and Guest House from natural gas heating to geothermal; add more solar to provide zero net energy; and add BESS. This combination of actions is intended to result in net zero energy for the two buildings. Other smaller residence and retreat buildings on campus will be brought to net zero in the future.

The Benedictine Women of Madison also intend to use third-party financing, so they do not need to pay for the added solar PV and portions or the geothermal system up front. They will also utilize available incentives. The financial goal will have the same annual cost for energy, including solar payments as they would have had without taking this action. These projections are not final as the planning is ongoing. They will eventually take over ownership of the systems at about year 12 (paying what is called by the IRS fair market value). At that point, they would no longer make monthly payments for solar energy. They would continue to pay for electricity purchased from the utility (mostly during the night and some cold winter days) and receive payment for excess solar sold to the grid.

Concluding Thoughts

These two examples are informative and inspiring. They demonstrate how decisions to transition to net zero energy consider sustainability, the situation with new and existing buildings owned by the congregations, the financial realities, and new technologies and financing tools that hold out the potential for making the transition to a sustainable physical plant while holding monthly energy costs in check and reducing them over time.

The transition to net zero energy may well come in stages, as it has at Holy Wisdom Monastery. For some existing buildings using natural gas for heating that are new or have had the heating and cooling systems recently replaced, the next stage might be to achieve net zero energy for electricity use, while leaving an efficient natural gas heating system in place. The switch from natural gas would remain for some logical point in the future. That’s the situation for some other buildings at the Dominican’s campus that currently heat with natural gas.

The game plan, however, remains the same. Congregations can follow Laudato Si’ and look down the path. Plan for a sustainable future and take action at those points in the future where it is doable for the congregation considering financial constraints.



For more information, or to have a consultation regarding how these strategies may be applied to your campus, please feel free to reach out to Hoffman to see how this could be implemented for your congregation.

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