This repository contains code to simulate HVAC systems (e.g. heat pumps) for homes to evaluate their utility costs and greenhouse gas emissions using real historical weather data.
You can try it out on https://shouldiheatpump.ca/
The idea and implementation were inspired heavily by https://heatpumpshooray.com/
This repository contains two main things: an HVAC simulation library, and a web application for a heat pump calculator.
The HVAC simulation library simulates on a 20 minute time step over long spans of time (up to a year with current weather data).
At each time step, the simulator...
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Uses a simulated thermostat to decide whether to turn heating or cooling equipment on or off based on historical weather data and a simulated internal temperature.
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If equipment is turned on, the simulator calculates the BTU/hr thermal power of each appliance, along with its fuel usage (electricity, gas, etc.)
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Based on a model of building geometry, weather conditions, and time-of-day, the passive thermal loads on the house are calculated in BTU/hr. This includes conduction, convection, infiltration, solar gain, and occupant body heat.
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At the end of each time step, the BTU/hr from the HVAC equipment and the BTU/hr from passive thermal loads are multiplied with the duration of the timestep to get a net BTU change for the time step. Using an estimated thermal mass of the house, this is used to update the indoor air temperature for the next time step.
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At the end of each time step, energy usage is recorded into monthly bills, using configurable utility tariffs.
At the end of the simulation, utility bills are tabulated, and emissions are calculated based on fuel usage.
The library is designed to be extremely flexible. Custom HVAC devices can be created, custom thermostat algorithms can be applied, and time-of-use pricing can be implemented for utility bills.
The web app uses the above simulation library to calculate utility bills for Canada on https://shouldiheatpump.ca/. To set up the simulation, we gather weather and utility cost information for Canada, and automatically select an air-sourced heat pump based on the specific situation of the simulated home.
Weather information was sourced from the ECMWF ERA5 hourly dataset.
2023 weather data for the majority of Canada was downloaded as a 2GB binary file, then split into many JSON files (one per 3-letter prefix of a postal code), compressed, and uploaded to S3. This allows the web app to use real weather data without needing a server.
Performance data for heat pumps is sourced from the NEEP Cold Climate Air Source Heat Pump Database.
There are many heat pump calculators out in the wild, though none I could find seemed accurate and open source. While this repository is designed with Canada in mind, the core simulation library should work anywhere in the world.
If you're motivated to get a version of this calculator working in your country, feel free to fork this repository and make it happen!