How long does Class A have?

As my amps run on 230v I guess they draw 1/2 the current and 1/2 the power?

The current is halved, but the voltage is doubled since :

Power = Current x Voltage

and it is a wash.  You'll get a lower voltage drop though, since

V = Current x R

therefore the voltage at your outlet will sag less for the same power.

Fortunately for the planet, big iron Audiophiles are a dying breed. We’ll self select ourselves out of being important.

In California a combination of power crunch and environmental factors have caused the state to mandate energy efficiency for new pre-built PCs. Sales of those far outweigh the hobbyist PC gamer/builder. This is kind of an analog for the audio hobbyist.

They aren’t coming for your tubes let alone Class A amp for a long long time.

Lastly the issue isn’t how much you consume it’s how it is generated. Get yourself a nice solar power source and you’ll be just as environmentally conscious as anyone else.  Who knows maybe even the micro-pellet nuclear reactors will come into vogue. :)