UK plans to ban the sale of new diesel and petrol cars by 2030 to be replaced by electric vehicles (EVs). The question is, will the UK’s electrical grid infrastructure ready for this change? This comparative study investigates the effect of UK green vehicles on the electrical grid and presents a new insight into improving their energy demand and carbon dioxide (CO2) emissions to the electrical grid. The results show that even when there is a very high level of market penetration of EVs, the overall effect on annual energy consumption may seem minimal. On the contrary, the effect that EVs may have on the electrical grid is dependent on the time-of-day EVs are being charged. Therefore, this study concludes that measures need to be put in place to control charging times of EVs and this would help restrict the total daily electricity and electrical energy demands. The introduction of EVs reduces the overall CO2 emissions mainly because a proportion of petrol and diesel cars are replaced by EVs. However, CO2 emissions can only reduce up to a certain level and this reduction of CO2 will have less effect due to an increasing number of EVs in the electrical grid. To reduce CO2 emissions further, the electricity that relies on high-carbon fossil fuels in the electrical grid should be set at the minimum level.