might control lighting, while another one controls heating and monthly bill within a given scale (Sidewalk Labs, 2017a: 44, 204 cooling, making it difficult to use simultaneous data to improve & 243). For example, if a dishwasher turned on at eight o’clock in efficiencies across both systems. To address these challenges, the evening, it could automatically wait until two in the morning to Sidewalk Labs proposed to set up a suite of energy “schedulers” run the wash, when the power is cheaper and cleaner. Of course, for the main actors responsible for buildings’ energy energy customers would always have had the option to override management (that is, building managers, office tenants, and the scheduler and pay more for utilities that specific month. residents) (Sidewalk Labs, 2017a: 44, 205 & 243). Schedulers would have helped to manage energy systems by integrating In essence, customers could have had total control and relevant data from building systems to improve coordination transparency vis-à-vis their utility costs and choice of power (Sidewalk Labs, 2017b: 314-323). generation sources and storage, and their monthly utility bills would also have been predictable (thanks to the combination For example, the building energy system could incorporate of the schedulers, the Perform application, and a greater external data sources such as occupant temperatureefficiency in management of the power grid). preferences, building occupancy rate, weather forecasts, and real-time energy prices, allowing different actors to improve 5.5 Using clean energy to heat and cool buildings their decision-making processes in a consistent way. The combination of passive building design and the active Sidewalk estimated that, in addition to conserving energy, the energy management systems through the Perform application schedulers could reduce building energy costs by up to twenty and the schedulers could have dramatically reduced the need percent (Sidewalk Labs, 2017). The company calculated that, at for heating and cooling. However, they could not have entirely the scale of the IDEA District, its approach could reduce GHG eliminated the need for heating, especially in a cold-weather emissions by an additional 0.03 tons per capita. climate like Toronto. 5.4 Making full electrification affordable The buildings in Toronto that have been constructed according to conventional principles require substantial heating, often In Toronto, the population draws power from a main centralized distributed back to the central heat generation plant, which electricity grid. In addition, strong public policy programs have leads to heat losses along the way. Sidewalk Labs proposed to helped the city to achieve very clean electricity generation deploy a new type of district energy system called the “thermal (Sidewalk Labs, 2017). grid.” This grid was designed to help realize full electrification in an affordable way, designed as a zero-fossil-fuel system In fact, at off-peak hours, the grid can run primarily on CO-free2 that relied on almost-clean energy from variable sources (for sources, including nuclear, hydro, and renewables. However, example, geothermal, excess heat, and wastewater heat). during peak times, when electricity demand is high, the grid uses a bigger portion of natural gas. This power source, For example, Sidewalk Labs planned to capture and repurpose in addition to being one of the most expensive (in terms of buildings’ waste heat to provide heating and generate domestic marginal cost), increases the GHG intensity of Toronto’s power hot water. In doing so, “buildings could then use heat recovered consumption by a factor of up to fifteen (Sidewalk Labs, 2017). from their wastewater system to preheat domestic hot water,”27 reducing the amount of energy needed by the building’s heat To overcome this challenge, Sidewalk Toronto planned to pump to increase the water temperature. collaborate with Toronto Hydro26 (the public electrical utility) to design an advanced power grid that would have integrated These kinds of solutions would have been implemented at the a “monthly budget” bill target, based on energy management scale of the IDEA District, and they would have enabled waste tools, and made use of solar power and battery storage in order heat captured from one space in a building to heat another to reduce the need to draw from the main grid at peak times. room at the same time. The mix of residential and commercial uses within buildings could have been used to create a situation The combination of the automation provided by the schedulers where 27 percent of the cooling and 31 percent of the heating and the availability of allotments in the electrical grid could have could happen simultaneously (Sidewalk Labs, 2017). enabled residents and businesses to self-select their preferred (26) https://www.torontohydro.com/about-us (accessed on 9 June 2021). (27) http://145881801-Sustainability-part-2-optimizing-building-energy-systems-part-1-creating-low-energy-buildings-part-3-making-full-electrification-affordable. html (accessed on 8 May 2020). 183 Quélin and Smadja | HEC PARIS | SMART CITIES | The sustainable program of six leading cities | 2021