This web app collects the data automatically and updates each day from Octopus Energy using its public API. It then uses that data to perform calculations based on the data you add to the form.
When you switch to Octopus you are placed on the fixed tariff - email them immediately and asked to be switched to the tracker tariff
When you don't have a smart meter your costs are based on your average daily consumption.
If you want to use electricity at any time of day or night then the tracker tariff is by far the cheapest tariff at the moment ( May 2020 )
The Octopus Tracker will take your annual consunption and estimate how your consumption varies over the year. This might be fairly accurate for gas consumption for cooking, hot water and central heating, but I doubt if their consumption estimate is accurate for charing an electric car, which will probably be more constant through the year.
Electricity cost with Octopus tracker
Gas costs with Octopus tracker
You can also compare the costs for Octopus Agile tariff