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effects. Usually, this type of tariff applies a surcharge if the power demand is higher than a certain
threshold. Such tariff has been tested or applied in various experiments and cases to constrain peak
demand (Baldick, 2018; Zarnikau, 2014, 2013) but remains a poor indicator to coincide a customer’s
maximum demand with the system or local congestions (Borenstein, 2016; Hogan and Pope, 2017).
Peak-coincident pricing is more suitable for solving congestion problems, associating the peak
rate with consumptions occurring during system congestion hours (MIT Energy Initiative, 2016;
Morell-Dameto et al., 2023). Abdelmotelleb et al. compare the response outcome of four different
network charges, including the peak-coincident charge, showing that this design led to higher system
economic efficiency (Abdelmotteleb et al., 2018). When applied to large industrial consumers with
foreseeable peak load patterns, peak-coincident pricing drives is close to welfare optimizing behavior
(Baldick, 2018). Azarova et al. test such tariff components on households showing that coincidental
peak charges are the main factor for savings due to the random and short-term overlapping usage of
several appliances (Azarova et al., 2018). However, the dataset (765 households) limits the scope of
the analysis and only partially reveals how tariff designs affect categories of households. Peak-
coincident pricing is efficient enough to apportion system costs across users in times of scarcity, but
they do not distinguish between individual load contributions that effectively cause aggregated
scarcity. Furthermore, while literature has covered optimal peak tariffs approximating them to
forward looking long term marginal cost (Morell-Dameto et al., 2023), the cost distributional effects
among consumers and the pathway towards them has not been in detail.
Time-based volumetric tariffs take their point of departure into system conditions reflecting
system peaks, while individual pricing, whether coincidental or not, departs from individual peak
loads. However, existing literature on grid tariffs neglects to investigate the notion of “peak” itself.
To our knowledge, there is no clear definition of what a peak is, or rather when a system or
household's demand is considered in a peak state. The closer a system operates on the technical
boundaries, the likelier it is in a peak state. An aggregated system peak is the sum of all individual
contributions, while some individuals use more capacity than others. Most time-based volumetric
tariffs, however, treat each individual contribution the same. Consequently, the pricing mechanism
in time-based volumetric tariffs treats the potential exclusion of certain grid users due to limited grid
capacity in a uniform manner through marginal pricing. This approach doesn't differentiate
adequately between individuals who contribute significantly to the scarcity and those whose
contributions are comparatively lower.
The notion of using 5% to define system peaks in the U.S. and Europe has been well established
in the policy literature, thanks to the work of Faruqui et al. (Faruqui et al., 2010, 2007). Koranyi
justifies this threshold by explaining that the 5% corresponds to approximately 400 hours during
which 90% of the total installed capacity in the U.S. is utilized (Koranyi, 2011). Past studies also use
peaker capacities on the supply side as a reference to define the number of hours when peak rates
should apply (Milligan et al., 2017). Many time-based volumetric tariffs build upon the load duration
curve as their foundation. They achieve this by designating a subset of hours that surpass a specific
aggregated installed capacity threshold. This subset of hours is used to symbolize the proportion of
annual hours linked with peak periods.
The notion of threshold is also relevant at the individual level. In this case, the underlying
question becomes how to define individual peak usage, which comes down to deciding what
differentiates a “normal" consumption behavior from a peak behavior. Concretely, a consumer's
maximum capacity threshold is limited by her physical capacity connection to the grid. Nevertheless,
suppose each consumer connected to the same line can consume up to the limits of their individual
physical capacity. In that case, it is not true that they can all do so simultaneously. Fausto et al. and
Pérez-Arriaga et al. suggest symmetric pricing varying across consumers dependent on the state of
the grid but also factoring in varying contributions to the aggregated peak (Fausto et al., 2019; Pérez-