To develop a NZ roadmap, it is important to forecast a current (see section 7.10) and future energy and carbon emissions baseline for a building(s) and/or estate in order to determine a business-as-usual scenario (see section 7.9) and to determine a representative rate of decarbonisation that would be required to align with target deadlines (see section 7.8). As part of this forecasting, it is important to consider factors that will affect future energy consumption and associated carbon emissions.
One of the most significant factors that will affect future carbon emissions from electricity consumption is Grid Decarbonisation, which reflects that increasing amounts of renewables contributing into the National Grid are going to result in the amount of carbon emissions associated with electricity consumption reducing per unit of electricity consumed over time. It is important that the impact of grid decarbonisation is modelled as this will have an increasing impact over time on the types of decarbonisation options that will be required to reduce carbon emissions - in practice this will mean that resource should be prioritised on the decarbonisation of heat (from fossil fuels) and shifting heating to electrically sourced solutions, if viable alternates such as converting fossil fuel heating to green hydrogen are not available.
Guidance and emissions factors for modelling Grid Decarbonisation on individual projects, building(s) and/or estates is available from the Green Book Supplementary Guidance: Valuation of Energy Use and Greenhouse Gas Emissions for Appraisal - see Appendix 4 for relevant link. This contains electricity emissions factors to 2100 (in kgCO2e / kWh). This guidance contains long-run marginal emissions factors that should be used for measuring small changes in consumption or generation, and grid average emissions factors which are used for foot printing.
Other factors that can affect future energy consumption and carbon emissions, include:
> Changes in building use or occupancy patterns
> Current or planned energy reduction projects
> Improvements in technology performance (i.e. energy performance)
Where possible these factors should be considered as part of any modelling on future energy and carbon emissions.