3.1.4. Electricity Tariffs

In order to quantify the impact of different electricity tariffs on the flexibility potential of electric vehicles, three tariffs are used in this case study.

The first tariff is a constant tariff '*Con*' in which the electricity price does not vary. The price is set to 0.19 \$/kWh, which was the average electricity price in California in 2018 [23].

'*ToU'* tariffs are offered throughout the United States and in other countries to motivate the reduction of electricity consumption in peak demand periods. Southern California Edison offers multiple *ToU* tariffs for residential customers on their website. For the simulations, the 'ToU-D-Prime' tariff as published on the website in the beginning of 2020 has been used. The tariff differentiates between winter and summer, weekday and weekend, and hour of day. In the winter, weekdays and weekends are priced equally. Between 4 and 9 p.m. the mid-peak tariff is active during the entire winter (0.36 \$/kWh) and on weekends in the summer (0.27 \$/kWh). During the summer, on weekdays from 4 to 9 p.m., the on-peak tariff for 0.39 \$/kWh is active. From 9 to 4 p.m. the off or super-off-peak tariff at 0.14 and 0.13 \$/kWh is active. This tariff motivates customer to reduce their electricity consumption in the late afternoon and early evening.

The third tariff integrated in this analysis is *RTP*. California already implemented two *RTP* programs in 1985 and 1987. However, both *RTP* programs had been canceled by 2003 [16]. Nowadays, California only offers *Con* and *ToU* tariffs. Therefore, a publicly available *RTP* tariff from ComEd, an energy supplier in Illinois, US is chosen [24]. In order to equalize the electricity prices for all tariffs, *p*RTP,offset is added to the real-time prices. *p*RTP,offset is the equal to the constant electricity price of 0.19 \$/kWh minus the mean of all RTP. Since an analysis of the forecasting error of *RTP* is beyond the scope of this publication, the *RTP* tariff is assumed to be a perfect forecast of the electricity prices.

$$p\_{\text{RTP,offset}} = p\_{\text{Con}} - \frac{1}{N} \sum\_{t=1}^{T} p\_{\text{RTP,i}} \tag{17}$$
