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→‎Short answer
(Accounted for the different GHG of different fuels. I still plan to refactor the calculations so the steps are less awkward.)
 
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==Short answer==
==Short answer==
<big>'''Yes.'''</big>


'''Yes.'''
The carbon emissions, compared to a gasoline car, are approximately:
* 135% for coal power plants
* 89% for ''older'' natural gas power plants {{light|(more common)}}
* 56% for ''newer'' natural gas power plants {{light|(less common)}}


The carbon emissions are '''about the same''' as gas cars, if the electricity is generated by
==Long answer==
* coal power plants
* ''simple'' natural gas power plants


For ''advanced'' natural gas power plants, which are more efficient, best-case carbon emissions are about '''half''' of what they'd be from driving a gas car.
The following calculations compare the average gasoline-powered vehicle with the average [[lithium-ion battery]]-based electric vehicle. Greenhouse gas emissions are in tonnes CO<sub>2</sub> equivalent (CO2eq):


==Long answer==
<!-- TODO: add a popup box for assumptions:
* no jevons paradox
* battery is the main difference in production emissions (EV as compared to gas car) (amortized over lifespan)
-->
 
'''Usage emissions''' <!-- not technically a heading. we don't want mediawiki to generate a table of contents. -->


''For coal power plants:''
{{dp
{{dp
|<nowiki>electric_car.efficiency</nowiki>
|<nowiki>electric_car.fuel_economy_equivalent</nowiki>
|<nowiki>100 miles per 34.6 kWh</nowiki>
|<nowiki>100 miles per 34.6 kWh</nowiki>
|<nowiki>The "gas mileage" equivalent for an average electric car.</nowiki>
|<nowiki>The "gas mileage" equivalent for an average electric car.</nowiki>
Line 39: Line 45:
|<nowiki>coal_power_plant.efficiency</nowiki>
|<nowiki>coal_power_plant.efficiency</nowiki>
|<nowiki>33%</nowiki>
|<nowiki>33%</nowiki>
|<nowiki>How much of the coal's heat energy becomes electricity</nowiki>
|<nowiki>How much of the coal's combustion heat energy becomes electricity</nowiki>
|<nowiki>Transformative Power Systems | Department of Energy</nowiki><br /><nowiki>
|<nowiki>Transformative Power Systems | Department of Energy</nowiki><br /><nowiki>
https://www.energy.gov/fecm/transformative-power-systems</nowiki>
https://www.energy.gov/fecm/transformative-power-systems</nowiki>
}}
{{dp
|natural_gas_power_plant.efficiency
|33%
|How much of the gas combustion heat becomes electricity
|This stat is for simple (older tech) natural gas power plants. The efficiency is the same as for coal and nuclear power. The process is the same: Heat boils water, creates steam to drive a turbine.
}}
}}
{{dp
{{dp
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|<nowiki>25.4 miles per gallon gasoline</nowiki>
|<nowiki>25.4 miles per gallon gasoline</nowiki>
|<nowiki>Gas mileage of an average American new car</nowiki>
|<nowiki>Gas mileage of an average American new car</nowiki>
|<nowiki>This datapoint is conformable with [electric_car.efficiency], because the calculator understands 'gallon gasoline' as an energy unit.</nowiki><br /><nowiki>
|<nowiki>This datapoint is conformable with [electric_car.fuel_economy_equivalent], because the calculator understands 'gallon gasoline' as an energy unit.</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
Citation:</nowiki><br /><nowiki>
Citation:</nowiki><br /><nowiki>
"The average fuel economy for new 2020 model year cars, light trucks and SUVs in the United States was 25.4 miles per US gallon (9.3 L/100 km)."</nowiki><br /><nowiki>
"The average fuel economy for new 2020 model year cars, light trucks and SUVs in the United States was 25.4 miles per US gallon (9.3 L/100 km)."</nowiki><br /><nowiki>
- Fuel economy in automobiles - Wikipedia</nowiki>
- Fuel economy in automobiles - Wikipedia</nowiki>
}}
{{calc
|electric_car.efficiency * li_ion.charge_discharge_efficiency * (100% - power_grid.losses) * coal_power_plant.efficiency
|car.fuel_economy
|fuel_economy_if_coal
}}
<!--SCRAP: In other words, there's a ''very slight'' increase in overall fuel efficiency, but it's not much.-->
''For natural gas power plants'':
Some have the same efficiency as coal power plants (33%). Results would be about the same as above. {{x|Although in theory, coal and natural gas have different GHG emissions per unit energy{{x|which we didn't factor in, and maybe we should for best precision}} - in practice, they're about the same, due to [[natural gas#fugitive emissions]]. Both are close enough to gasoline, for the purpose of the calculations on this page.}}
''Other'' natural gas power plants {{light|(the more advanced "combined-cycle" type)}} are more efficient: up to 60%:
{{dp
|<nowiki>natural_gas_combined_cycle_power_plant.efficiency</nowiki>
|<nowiki>60%</nowiki>
|<nowiki>How much of the natural gas's heat energy becomes electricity, in an advanced "combined cycle" power plant</nowiki>
|<nowiki>This is considered a "maximum" value - the best natural gas power plants achieve this.</nowiki><br /><nowiki>
Simpler/older natural gas plants (no combined cycle) have only an efficiency of 33%, same as [coal_power_plant.efficiency].</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
Read more: https://energyeducation.ca/encyclopedia/Natural_gas_power_plant</nowiki>
}}
{{calc
|electric_car.efficiency * li_ion.charge_discharge_efficiency * (100% - power_grid.losses) * natural_gas_combined_cycle_power_plant.efficiency
|car.fuel_economy
|fuel_economy_if_advanced_natural_gas
}}
<!--SCRAP: In this case (electric car + advanced natural gas power), we do in fact cut our emissions in half. But this doesn't apply to older, simpler natural gas power plants.-->
{{dp
|<nowiki>ev.battery</nowiki>
|<nowiki>65.2 kWh</nowiki>
|<nowiki>Energy capacity of the average electric vehicle battery</nowiki>
|<nowiki>Useable battery capacity of full electric vehicles</nowiki><br /><nowiki>
https://ev-database.org/cheatsheet/useable-battery-capacity-electric-car</nowiki><br /><nowiki>
</nowiki>
}}
{{dp
|<nowiki>li_ion.ghg_by_energy</nowiki>
|<nowiki>73 kg / kWh</nowiki>
|<nowiki>Greenhouse gas emissions (CO2eq) of producing a lithium-ion battery</nowiki>
|<nowiki>"by energy" here means "by the size of the battery, defined by how much energy can be stored".</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
What is the environmental impact of lithium batteries? - Changeit ...</nowiki><br /><nowiki>
changeit.app › blog › 2021-03-26-environmental-impact-of-lithium-batteries </nowiki>
}}
}}
{{dp
{{dp
Line 163: Line 125:
}}
}}
{{dp
{{dp
|<nowiki>car.fuel_economy</nowiki>
|<nowiki>natural_gas_combined_cycle_power_plant.efficiency</nowiki>
|<nowiki>25.4 miles per gallon gasoline</nowiki>
|<nowiki>60%</nowiki>
|<nowiki>Gas mileage of an average American new car</nowiki>
|<nowiki>How much of the natural gas's heat energy becomes electricity, in an advanced "combined cycle" power plant</nowiki>
|<nowiki>This datapoint is conformable with [electric_car.efficiency], because the calculator understands 'gallon gasoline' as an energy unit.</nowiki><br /><nowiki>
|<nowiki>This is considered a "maximum" value - the best natural gas power plants achieve this.</nowiki><br /><nowiki>
Simpler/older natural gas plants (no combined cycle) have only an efficiency of 33%, same as [coal_power_plant.efficiency].</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
Citation:</nowiki><br /><nowiki>
Read more: https://energyeducation.ca/encyclopedia/Natural_gas_power_plant</nowiki>
"The average fuel economy for new 2020 model year cars, light trucks and SUVs in the United States was 25.4 miles per US gallon (9.3 L/100 km)."</nowiki><br /><nowiki>
- Fuel economy in automobiles - Wikipedia</nowiki>
}}
}}


''For a gasoline car'' {{light|(typical usage)}}:
{{calc
|average_us_vehicle.mileage_by_time / car.fuel_economy * gasoline.ghg_by_energy
|tonnes/year
|usage_emissions_if_gasoline_car
}}


'''So far,''' we still haven't counted the environmental impact of ''making'' an electric car, which is significantly more than for a gasoline-powered car:


''For an EV charged by '''coal''' power plants'' {{light|(same amount of driving as above)}}:
{{calc
|average_us_vehicle.mileage_by_time / electric_car.fuel_economy_equivalent * coal.ghg_by_energy / coal_power_plant.efficiency / (100% - power_grid.losses) / li_ion.charge_discharge_efficiency
|tonnes/year
|usage_emissions_if_EV_coal
}}


For simplicity sake, we're just going to count the emissions of making the batteries, and assume that making the rest of the car would take roughly the same emissions as making a gasoline-powered vehicle: {{x|Technically, the assumption is that the emissions ''divided by lifespan'' are about the same. Gasoline vehicles are more complex than batteryless EVs, but also have a longer lifespan.}}:


''Estimate for [[lithium-ion]] electric cars:''
''For an EV charged by '''natural gas''' power plants'' {{light|(same amount of driving)}}:
{{calc
{{calc
|ev.battery * li_ion.ghg_by_energy / ev.lifespan
|average_us_vehicle.mileage_by_time / electric_car.fuel_economy_equivalent * (natural_gas.ghg_by_energy + natural_gas.fugitive_ghg_by_energy) / natural_gas_power_plant.efficiency / (100% - power_grid.losses) / li_ion.charge_discharge_efficiency
|tonnes / year
|tonnes/year
|battery_ghg
|usage_emissions_if_EV_natural_gas
}}
}}


''Now compare for the gasoline a non-electric car would burn, on average:''
 
''For an EV charged by advanced {{light|(combined-cycle type)}} natural gas power plants'' {{light|(same amount of driving)}}:
{{calc
{{calc
|gasoline.ghg_by_energy * average_us_vehicle.mileage_by_time / car.fuel_economy
|average_us_vehicle.mileage_by_time / electric_car.fuel_economy_equivalent * (natural_gas.ghg_by_energy + natural_gas.fugitive_ghg_by_energy) / natural_gas_combined_cycle_power_plant.efficiency / (100% - power_grid.losses) / li_ion.charge_discharge_efficiency
|tonnes / year
|tonnes/year
|gasoline_ghg
|usage_emissions_if_EV_advanced_natural_gas
}}
}}


''Now, for coal power plants charging EVs, same amount of driving:''
{{calc
|coal.ghg_by_energy * average_us_vehicle.mileage_by_time / fuel_economy_if_coal
|tonnes / year
|coal_ghg
}}


''Now, for advanced natural gas power plants charging EVs, same amount of driving:''
'''Battery production emissions''' <!-- not technically a heading. we don't want mediawiki to generate a table of contents. -->
{{calc
 
|(natural_gas.ghg_by_energy + natural_gas.fugitive_ghg_by_energy) * average_us_vehicle.mileage_by_time / fuel_economy_if_advanced_natural_gas
So far, we still haven't counted the environmental impact of ''making'' an electric car, which is significantly more than for a gasoline-powered car.
|tonnes / year
 
|advanced_natural_gas_ghg
For simplicity sake, let's assume that ''batteries'' account for the entire difference between electric cars and gasoline cars, in terms of GHG emissions of ''production'' divided by vehicle ''lifespan''. {{x|A gasoline vehicle is a bit more complex than a batteryless EV, but the former also has a longer lifespan.}}
 
{{dp
|<nowiki>ev.battery</nowiki>
|<nowiki>65.2 kWh</nowiki>
|<nowiki>Energy capacity of the average electric vehicle battery</nowiki>
|<nowiki>Useable battery capacity of full electric vehicles</nowiki><br /><nowiki>
https://ev-database.org/cheatsheet/useable-battery-capacity-electric-car</nowiki><br /><nowiki>
</nowiki>
}}
}}
 
{{dp
''Add the battery emissions:''
|<nowiki>li_ion.ghg_by_energy</nowiki>
{{calc
|<nowiki>73 kg / kWh</nowiki>
|battery_ghg + coal_ghg
|<nowiki>Greenhouse gas emissions (CO2eq) of producing a lithium-ion battery</nowiki>
|tonnes / year
|<nowiki>"by energy" here means "by the size of the battery, defined by how much energy can be stored".</nowiki><br /><nowiki>
|total_ghg_if_coal
</nowiki><br /><nowiki>
What is the environmental impact of lithium batteries? - Changeit ...</nowiki><br /><nowiki>
changeit.app › blog › 2021-03-26-environmental-impact-of-lithium-batteries </nowiki>
}}
}}
 
''For battery production:''
{{calc
{{calc
|battery_ghg + advanced_natural_gas_ghg
|ev.battery * li_ion.ghg_by_energy / ev.lifespan
|tonnes / year
|tonnes/year
|total_ghg_if_advanced_natural_gas
|battery_emissions
}}
}}


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'''''Now, for the final comparison:'''''
'''''Now, for the final comparison:'''''
{{calc
{{calc
|total_ghg_if_coal
|usage_emissions_if_EV_coal + battery_emissions
|% gasoline_ghg
|% usage_emissions_if_gasoline_car
}}
}}


{{calc
{{calc
|total_ghg_if_advanced_natural_gas
|usage_emissions_if_EV_natural_gas + battery_emissions
|% gasoline_ghg
|% usage_emissions_if_gasoline_car
}}
}}


Thus, with coal power, emissions are worse than driving a gasoline-powered car. But for ''advanced'' natural gas power plants, emissions are about half. In either case, this doesn't count the other environmental impacts {{light|(non-CO<sub>2</sub>)}} of mining lithium & cobalt.
{{calc
|usage_emissions_if_EV_advanced_natural_gas + battery_emissions
|% usage_emissions_if_gasoline_car
}}


<!-- TODO: redo this with more precision: coal.ghg_by_energy and natural_gas.ghg_by_energy? but then what about fugitive emissions? maybe make a datapoint "natural_gas.fugitive_ghg_by_energy" that factors it in -->
Thus, with coal power, emissions are ''worse'' than driving a gasoline-powered car. But for ''advanced'' natural gas power plants, emissions are about ''half''. In either case, this doesn't count the other environmental impacts {{light|(non-CO<sub>2</sub>)}} of mining lithium & cobalt.


Maybe there would be a good case for fossil-fuel-electricity-powered vehicles if [[carbon capture and storage]] could be fully & safely applied to the power plants.
Maybe there would be a good case for fossil-fuel-electricity-powered vehicles if [[carbon capture and storage]] could be fully & safely applied to the power plants.


<!-- SCRAP: When that's factored in, there's probably no benefit to having an electric car in the coal-power scenario, and only ''moderate'' benefit in the advanced-natural-gas-power scenario. -->
<!--
<!--
  TALK: add scenario where fuel-cell vehicles are powered by hydrogen gas made from fossil fuels?
  TALK: add scenario where fuel-cell vehicles are powered by hydrogen gas made from fossil fuels?
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