Energy Modelling

EnergySizer – An Environmental and Economic Optimization Simulator for Energy

Many building and facility owners are interested in cost effective ways to reduce energy costs. Onsite power generation systems such as combined heat and power (CHP) or solar PV can often accomplish this goal, while at the same time achieving significant reductions in greenhouse gas emissions. The advantages of onsite power generation have been demonstrated for many years in Europe.

Sizing the solution is important to ensure the best possible return on investment. For example, larger CHP units have lower cost per kW of output. Too small of a unit will result in higher cost per kW and a lower return on investment (ROI). However, if a unit is too large the building will not be able to effectively utilize the heat produced and with the higher fuel consumption the ROI will decrease.

For each facility, there is an optimal size for an onsite energy producer that maximizes the ROI.

Most CHP vendors approach CHP sizing with a simplistic “rule of thumb” approach.  They assume that most buildings can use the heat for some given amount of the time. Without considering the actual electricity and heating profile, the CHP can be improperly sized resulting in lower savings.

The EnergySizer eliminates the guess work and assumptions in sizing the onsite energy producer project to optimize the savings and the return on investment.


EnergySizer results in a solid understanding of the economic, environmental and energy performance of an energy producer project for a facility as well as providing an understanding of the impact on the ROI of changing electricity and natural gas rates (as well as other risk factors).

How it Works

EnergySizer first creates a computer model of the facility and imports the actual electricity and natural gas data, either monthly totals from the utility bills or hourly data from the utility provider (if available). The model also incorporates an understanding of the existing systems, the efficiency of the current boiler, the maximum operating time an energy producer, and the current electricity delivery model (fixed rate, net metering, peaking, block contracts).

In some projects, only the monthly electricity and natural gas data are available. In these cases, we must estimate the hourly consumption in order to ensure the energy producer is properly sized.  This is accomplished by applying a “profile” to the daily/weekly consumption patterns. EnergySizer has built in profiles for typical office towers, hotels, community centres, residential buildings and greenhouses.  Customized profiles can also be created to appropriately model the specific consumption patterns of a facility.

The result is a detailed model of the facility electricity and gas consumption.  The red line shows the facility demand while the blue line shows the CHP production.  Best practice suggests that the energy producer be selected to

  • minimize the times the electricity production above the facility demand (unless the facility can net meter)
  • minimize the times the heat production exceeds the facility demand (unless the excess heat can be used for other purposes such as cooling)


Once a model has been created, the analyst will set the rates for electricity and natural gas for the facility. As the electricity and natural gas rates can vary over time, the analyst can adjust these rates and interactively visualize the impact on the ROI.

The objective of EnergySizer is to optimize the size of the energy producer to maximize the ROI or to minimize the green house gas (GHG) emissions.  The analyst can interactively adjust the Energy Producer size and observe the resulting operational parameters, including

  • the number of operating hours
  • the amount of electricity the facility would consume and the amount exported to the grid
  • the amount of heat that the facility would consume from the energy producer
  • the micro-utility threshold – an indicator of the kg GHG/MWh

The results of the EnergySizer model are provided for the analyst.  This shows the cost difference of operating without the Energy Producer compared to operational costs with the selected Energy Producer.  This results in the savings per year.


Once an Energy Producer is sized to maximize the ROI, EnergySizer can then forecast the financial returns for the solution.