A picture of our net-zero solar home modeled in 3D showing the sun's travel throughout the year.

Energy modeling is a common phrase in conversations about sustainability and clean energy. However, many people need help understanding the concept since it’s complex. So what is energy modeling all about?

Energy modeling analyzes a building’s energy consumption by collecting relevant data and feeding it into simulation software. After processing the data, the software predicts energy consumption and highlights optimization opportunities.

Read on to understand how energy modeling works, why you should do it, and what it costs.

What Is Energy Modeling?

You’ve probably heard of energy modeling if you’re interested in building or HVAC design, sustainability practices, green certifications, and other similar subjects.

This relatively new concept is a significant improvement in the energy industry, but how exactly does it work?

Energy modeling means simulating the energy usage of a building or HVAC system with software that analyzes multiple aspects of the energy system and generates crucial information to optimize new and existing buildings.

Energy models allow engineers and contractors to compare energy consumption in different scenarios with software-generated data.

That helps reduce construction and operations costs for new buildings and improve the efficiency and sustainability of existing buildings.

How Energy Modeling Works

The software needs input to generate results, which usually include a large amount of information about a building and its energy requirements, including:

  • Building geometry
  • Building materials
  • Heating and air conditioning
  • Water heater
  • Lighting
  • Renewable energy system configurations
  • Thermostat settings
  • Building use
  • Occupancy schedule
An energy model with a calculator, laptop keyboard, and pencils scattered about
Energy modeling takes into account all factors of a building’s efficiency.

The software will apply complex equations to the above information and account for factors like the weather and climate of a place.

Next, the software displays detailed and comprehensive results outlining energy usage and costs, thermal loads, and strategies for maximum comfort for the occupants.

How Accurate Are the Models?

Given the comprehensive nature of the input data and the complexity of the processing done on the data, energy models are generally considered very accurate.

However, as with all predictive models, there’s always a small margin of error, which is something to keep in mind.

For example, a building may be used for purposes different from what was intended, the building material may be changed at the last minute, or the weather patterns will deviate from the prediction.

Energy models that rely on machine learning have an even higher degree of accuracy, with the predicted energy usage deviating from actual energy usage at 0.01 – 6.16 percent!

To better understand this range, a deviation of 6.16 percent is where the predicted energy consumption in kilowatt-hours (KWh) is 1734 compared to an actual consumption of 1633.

With such accuracy, these models are useful.

What Is the Purpose of Energy Modeling?

The purpose of energy modeling is to give you accurate information about the energy efficiency of a building, its cost, and environmental impact by creating a software simulation of a building’s energy usage.

The software generates data to build efficient and sustainable housing.

Additionally, the modeling helps optimize energy use at a larger scale. It informs energy efficiency programs and sustainability policies.

Our Own Netzero Solar Home Energy Model

When I set out to try to create the most affordable netzero home I could, I actually found an energy modeler freelancer on Upwork of all places. They did an amazing job as well.

The goal for the house was to figure out roughly what kWh (electrical energy usage) the end design house would use, given the home’s exposure to the sun in specifically Cape Coral, FL where it was located. The engineer ran all kinds of numbers, and there are tons of variables involved. These can include:

  • Amount of sunshine per year
  • Square footage of the house
  • Mechanical assumptions for water heating, HVAC, and others
  • Surface area of glass windows vs. walls (windows are incredibly inefficient and let a lot of heat in)
  • Ambient temperature of the incoming city water
  • R Values of all the insulation in ceilings, walls, and potentially in the floor.
  • Lots more..

Here are some photos from the energy modeling he did as well. You can see the mock solar system and the direction of the sun patterned throughout the year:

Energy Modeling Levels

There are levels to energy modeling. Not all projects need an extremely detailed energy model that takes weeks to complete.

You can choose one of three modeling levels depending on what you want and how much you’re willing to spend.

A man's hand holding a light bulb full of money against paperwork with energy assessments
You can select from three levels of energy modeling at various price points.

Level 1

This is a basic level of modeling that takes three or four days and costs the least.

Typically, this energy modeling is useful during the early design phase and for estimating a particular aspect of the building rather than the whole structure.

Energy models of this level require the least amount of input data.

Level 2

This level of modeling is used to analyze the energy usage of buildings and systems and its impact. It requires detailed input about the building and information about yearly weather patterns.

As a result, it takes up to two weeks to complete and costs more.

Level 3

The most advanced level of modeling is also called 8760 modeling, named after the total number of hours in a year.

Energy modeling of this scale uses a year’s worth of highly detailed data about the building materials, components, occupancy, and purpose of use, as well as information about the weather patterns.

It takes up to a month and has the highest cost.

How Much Does Energy Modeling Cost?

It’s not easy to determine the cost of energy modeling because a big part of the cost depends on the type and size of the building being modeled and the level of energy modeling.

A basic energy model for a small building can cost around $2,500. On the other hand, massive structures with many more factors to take into account and data to input into the software can cost up to $200,000.

While the cost of modeling may seem too high, the resulting insights can save money in the long term.

A man holding an illuminated light bulb calculates energy savings
Energy modeling can be costly, but the results are worth it.

Studies have shown that the typical energy modeling payback is only a couple of months.

Energy modeling results make a significant difference in how the building is maintained and managed, saving energy and ensuring the comfort of the occupants.

Paying $200,000 may seem extreme for most of us, but considering the energy use of large buildings, it’s only a tiny percentage of the typical energy cost.

What Is an Energy Model Architecture?

An energy model architecture is the design approach that data scientists use when analyzing energy consumption in a building. An energy model can be black-box, grey-box, or white-box depending on the data.

Here are the three energy model architectures.

  • White-Box. This architecture uses complex physical equations to determine the energy requirements of a building and does not need historical data. It’s highly accurate. However, it uses a complex process and takes a lot of time. Since it relies on the physical qualities of a building instead of historical data, it can predict the energy requirements of a building that hasn’t been constructed yet.
  •  Black-Box. This approach relies on the historical energy consumption data about a building to predict future energy consumption and analyze the impact of energy-efficiency measures. It uses machine learning techniques like neural networks to process historical data and generate predictive models.
  • Grey-Box. This architecture combines simplified physics equations with some historical data. Simplifying the computation means less time is needed but reduces accuracy, which analysts compensate for by incorporating historical data. This approach is well-suited for building load estimation and optimization.

While it’s tempting to conclude that one architecture is better than another, all three architectures are helpful in different situations.

If you have plenty of historical data about a building’s energy usage and want to optimize it, the black-box approach would suit you best.

Conversely, the white-box approach is the way to go if you need more historical data.

Sometimes, the approaches are used in tandem. For example, an analyst might want to find out why the energy consumption differs from the expected consumption according to the physical properties of the building.

Energy Modeling in Architecture

Nowadays, when architects design buildings, they must consider the building’s energy performance and environmental impact. This is not easy.

Energy modeling makes the work of architects simpler by allowing them to incorporate energy efficiency into the design of new buildings.

While it’s true that the software-generated models are relatively creatively uninspiring, they leave space for the architect to put their artistic touch.

What Else Is Energy Modeling Used For?

Architectural design is not the only field where energy modeling is applicable or necessary. Several other areas require energy modeling for better planning, designing, and understanding the efficiency of systems.

Here’s an overview.

  • Performance ratings and certifications of buildings: Companies specialized in rating building performances or awarding green certifications can use energy modeling to assess different aspects of the building.
  • Design of HVAC systems: Engineers who design HVAC systems use energy modeling to create efficient design and operation strategies for complex systems.
  • Building-stock analysis: Energy modeling helps analyze models and strategies, providing valuable input for effective renovation strategies and efficiency programs.

How Can I Learn Energy Modeling?

As you can imagine, energy modeling is complex and requires extensive knowledge in different fields.

However, suppose you have some prior knowledge of building physics. In that case, you can attend special courses that teach you how to do energy modeling.

A group of three people assessing the energy efficiency of a windmill prototype
You can learn to model energy as a viable career choice or for more accurate energy assessments.

In addition to some basic qualifications, you should also know how to use different energy simulation software.

You can learn energy modeling through various online and in-person programs that teach modeling methodology. The typical course lasts six hours. The programs aim to prepare you to use modeling in real-time environments.

What Is Energy Simulation Software?

Energy simulation software is the primary tool in energy modeling. The software processes input data about a building’s energy use to predict energy consumption patterns and identify optimization gaps.

The output of energy simulation software includes predictions of several key aspects of a building energy system, including:

  • Annual carbon emissions
  • Annual energy consumption
  • Annual energy cost
  • Monthly energy bills
  • Different efficiency strategies
  • Comparison of efficiency options
  • Life cycle payback

You will get only some data types from the energy simulation software. Different types of software can provide more or fewer data depending on how thorough their analysis is.

What Projects Are Best Suited for Energy Modeling?

Technically, any project can be the subject of energy modeling if the required data is provided. However, not all projects can benefit from this tool.

Existing buildings with no plans for remodeling or expansion have very few ways of applying any energy modeling insights.

On the other hand, buildings that are being renovated or expanded and those that are about to be built have much more to profit from modeling.

The information and design strategies that this tool provides to architects and engineers can increase the efficiency and comfort of any building.

Conclusion

Energy modeling is a tool that ensures new and existing buildings or systems operate as efficiently as possible while providing maximum comfort to their occupants.

Modeling is used in several fields, including architectural design, HVAC design and production, building certification, and more.

The process uses simulation software that receives different types of input about the building, its purpose, and even the local weather patterns and then provides energy consumption predictions and strategies.

Depending on the analysis’s complexity and the building’s size, it can take a few days to a few weeks.

Sources

Science Direct: A Building Energy Consumption Prediction Model Based on Rough Set Theory and Deep Learning Algorithms | Department of Energy: The Shockingly Short Payback of Energy Modeling | Foresight Management: Building Energy Modeling | GoldSim: Introduction to Simulation Software | Attainable Home: Grants for Net Zero Homes – Government Energy Efficiency Programs | AIA: Architect’s guide to integrating energy modeling in the design process  | Department of Energy: Building Energy Modeling 101: Architectural Design Use Case | Energy Models: What is Energy Modeling & Building Simulation | Attainable Home: Is Energy Star Certification Worth It For Your Home? | Greensleeves Technologies Corp: 8760 Energy Model | Gresham Smith: Data-Driven Design: The Benefits of Building Energy Modeling  | Construction 21: The Role of Energy Modeling in Sustainable Design | ACS UK: What is HVAC and How is It Different From Air Conditioning?

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