You need service-providers-formerly-known-as-banks to manage issue/do due diligence in respect of producers, and a quasi-monetary authority by way of quality control.

That ensures that there aren't more sold than are capable of being produced.

You also need transparency in relation to the number in issue.

If speculators buy up and hoard units - which does not affect the physical market price btw - then they run the risk that when they want out the price they get is way below the spot price, because it will take years for buyers to consume that much, and they therefore require a discount in order to buy.

Units are Units are Units: KiloWatt hours are KiloWatt Hours. There is a common market custodian, and a single homogeneous pool of electricity production.

Re lots of different commodities it's no different to what we have now, except that instead of being exchanged for Units redeemable in intrinsically worthless fiat currency, we have a Unit redeemable in something with an intrinsic use value, that would be pretty much universally acceptable.

The exchange rate is whatever the market arrives at.

IMHO Bob Hahl makes a good case here for such a currency here

KiloWatt Cards

"The future is already here -- it's just not very evenly distributed" William Gibson