Abstract: A method of forecasting the combined impact the introduction of energy technology solutions will have on the energy consumption at a site, comprising: selecting a plurality of energy technology solutions suitable for use at the site; generating energy usage data for the site, the energy usage data comprising data usage for the site in predetermined time intervals over a predetermined duration; creating energy impact data for each selected energy technology solution for each predetermined time interval based on the energy usage data for that time interval; sequentially generating impacted energy data for each selected energy technology solution across each time interval, the impacted energy data generated for a preceding energy technology solution being used to generate the impacted energy data for a subsequent energy technology solution; following completion of the sequentially generated impacted energy data for each energy technology solution, summing for each time interval independently the impacted energy