> For the complete documentation index, see [llms.txt](https://docs.cscale.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cscale.io/the-c.scale-tm-data-model/whole-life-carbon/avoided-emissions.md). # Avoided Emissions The C.Scale model calculates the avoided emissions associated with surplus energy generated on-site through photovoltaic panels. The benefits from exported utilities (e.g., the avoided impact of grid electricity generation) are reported in Module D and as a separate model element called “Avoided Emissions.” Module D must be communicated separately from A-C impacts since it represents benefits outside of the system boundary of the building project. ## Calculation of avoided emissions from surplus energy generation Once production from an onsite solar array has exceeded annual electricity use, C.Scale assumes all additional energy generated by the array displaces the generation of electricity by the electrical grid. The avoided emissions from surplus onsite energy generation are calculated as the emissions that this displaced energy would have incurred. This method assumes that there is no curtailment of PV production and that the carbon emissions of grid electricity when solar energy is produced are substantially similar to the annual average emissions. In locations with a high proportion of solar on the grid, *these assumptions will not hold,* and skepticism of C.Scale's calculation of avoided emissions is warranted. Read more about curtailment in [this publication ](https://www.nrel.gov/docs/fy14osti/60983.pdf)(pdf) from the National Renewable Energy Laboratory. The assumption of displacement generation will not hold true in all locations, and some skepticism of this estimate is encouraged. Two interrelated situations where C.Scale's assumptions of displaced generation will not hold are when: * Daytime (i.e., when solar is available) emissions from the electrical grid are significantly lower than the national average. * Surplus energy generation is expected to be curtailed by the utility. For an overview of curtailment in the United States, we recommend [this report from NREL](https://www.nrel.gov/docs/fy14osti/60983.pdf) (pdf). The generation of excess energy by an onsite solar photovoltaic array displaces the generation an equivalent amount of electricity from the utility grid. This is calculated as follows: $$ Avoided\ carbon\ emissions=\ \sum\_{t=1}^{m}\ e\_{t}\ast c\_{t} $$ Where $$e\_{t}$$ is the excess energy in kWh generated in year $$t$$ and $$c\_{t}$$ is the carbon intensity of the electrical grid per unit demand in year $$t$$. This method assumes that there is no curtailment of PV production, and that the carbon emissions of grid electricity when solar energy is produced is substantially similar to the annual average emissions. In locations with a high proportion of solar on the grid, curtailment is likely and skepticism of C.Scale's calculation of avoided emissions is warranted. If you are interested in further analysis of hourly emissions, [please reach out](mailto:hi@cscale.io). --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.cscale.io/the-c.scale-tm-data-model/whole-life-carbon/avoided-emissions.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.