All the electricity in my city to normal households are from solar/wind/hydro power so using old hardware is definitely better for the environment for me to use old hardware over buying new. It hurts the wallet though.
Hydropower uses massive amounts of cement, and the cement industry is responsible for about 5% of all carbon emissions. Similarly, if you're counting the environmental impact of manufacturing the more energy-efficient computer, you must also count the environmental impact of the solar panels or wind turbines that do not have to be manufactured because of the increased energy efficiency.
Surely the one-time emissions in cement required to build a dam that lasts for decades amortizes down to nothing compared with the ongoing outputs associated with coal or gas fired electricity production? (not to mention the upfront emissions associated with constructing those facilities as well...)
Most of those global cement emissions are surely in building sidewalks, highways, bridges, and skyscrapers? Seems weird to blame an otherwise pretty green electricity source for this carbon.
Instead you are hurting the global environment (not your local environment).
If you use an extra kW, the city doesn't get to sell the extra kW into the national grid. So the national grid needs an extra kW, which is most likely produced by gas!
In a nationally connected electricity grid, each extra kW you use, increases the usage of the next marginal kW of power on the network, which is most likely gas (unless you use the kW during off-peak, when it might be nuclear depending on your country).
No. This is a fallacious misunderstanding of how markets work.
The hypothetical user of the older hardware is not damaging anyone else by consuming "green" electrons. Their demand provides a market for green projects, and the fact that there is non-green supply still available is simply an opportunity for new green supply to supplant it.
If the demand for green electricity is there, supply will appear, as long as it is economic to do so.
So you are suggesting there is two types of electricity markets: one for green electricity and another for say black electricity. Let's say their prices are in equilibrium.
So you increase your green electricity demand, and green power generation capacity is increased and more green electricity is made.
However the demand for black electricity hasn't decreased.
But you have created an arbitrage opportunity e.g. someone decreases their green electricity usage, and increases their black electricity usage.
Your fallacy is that you think it is possible to create two separate electricity markets (maybe separate grids, or strong regulation) for a good that is quite fungible.
For at least 10 years I have had a contract for "green energy" from my municipal supplier. They, in turn, contract to buy power from solar and wind suppliers to fulfill the consumption of those who are part of that program.
It does indeed work as I describe. And, because the wind and solar providers are among the lowest-cost providers at this point, "black" energy is losing market share quite quickly.
I understand electricity markets quite well and live and work in one of the most dynamic ones in N. America. This is how it works.