You cannot give one figure here. The only comparable metric is cost per km or equivalent consumption (which is basically the same thing in different units), which is function on 4 variables: ICE/BEV consumption and electricity/fuel price.
Fuel cost equivalent BEV consumption (expressed in fuel per distance, e.g. l/100km) is equal to [C_e * P_e] / P_f = C_e * [P_e / P_f]; where C_e = BEV electricity consumption; P_e = Price of electricity; P_f = Price of fuel.
With C_e = 20 kWh/100km; you need [P_e / P_f] ~= 0,35 to break even. With fuel prices in the [1.7 -- 1.9] range you need electricity prices in [0.59 -- 0.67] range.
Sibling comments list UK prices to be P_e = 0.65; P_f = 1.9; yielding equivalent consumption is 6.8 l/100km. (34.5 mpg according to google)
In my country prices are roughly P_e = 0.59; P_f = [1.65 -- 1.75] giving equivalent consumption of roughly [7.15 -- 6.75].
BEV consumption is a bitch for comparison. Your trip computer displays battery-to-controller consumption, which is what you pay at public charger, but when charging at home you pay for grid consumption which includes charging losses.
Fuel cost equivalent BEV consumption (expressed in fuel per distance, e.g. l/100km) is equal to [C_e * P_e] / P_f = C_e * [P_e / P_f]; where C_e = BEV electricity consumption; P_e = Price of electricity; P_f = Price of fuel.
With C_e = 20 kWh/100km; you need [P_e / P_f] ~= 0,35 to break even. With fuel prices in the [1.7 -- 1.9] range you need electricity prices in [0.59 -- 0.67] range.
Sibling comments list UK prices to be P_e = 0.65; P_f = 1.9; yielding equivalent consumption is 6.8 l/100km. (34.5 mpg according to google)
In my country prices are roughly P_e = 0.59; P_f = [1.65 -- 1.75] giving equivalent consumption of roughly [7.15 -- 6.75].
BEV consumption is a bitch for comparison. Your trip computer displays battery-to-controller consumption, which is what you pay at public charger, but when charging at home you pay for grid consumption which includes charging losses.