The equivalent ton of oil (toe) is the unit of energy most commonly used and which is used to make calculations and comparisons.
1 toe = 11.630 kWh = 41,868,000,000 joules
I.e., the amount of energy contained in a ton of oil is 11,630 kilowatt hours. With this data and other calculations comes to the following data:
1 Natural Gas Toe = 2.1 tons of CO2
1 Carbon Toe = 3.8 tons of CO2
1 Diesel Toe = 2.9 tons of CO2
With these data we can conclude for instance. If we build a solar power plant that produces 40,500 kWh per year, we would save 7.3 tons of carbon dioxide at no longer produce those watts in a carbon plant.
In simple words and numbers
1 kWh produced from natural gas emits 0.18 kg of CO2
1 kWh produced from coal emits 0.33 kg of CO2
1 kWh produced with Diesel emits 0.29 kg of CO2
1 kWh produced by the combination of all sources of renewable energy emits 0.04 kg of CO2