[tomxor]

I think you can swap "old desktop" for some smaller new power efficient mini desktop, which at idle (for basic home needs lets face it it's pretty close to idle) it's likely to draw way under it's max... but if you are so carbon conscious consider the total environmental cost, buying new shit (new mini desktop or consumer routers) that constantly needs replacing incurs a carbon cost through consumption that people rarely try to quantify because it's not so easy - but it's often still very big. Saving an old PC from the rubbish is free of this cost, it not only saves manufacturing carbon cost but environmental pollution.