Maximum supply ever will be 500 millions but number of circulating will depend on few things like how many will be locked in smart contracts under borrowing definition in future to others. Once its usage goes at larger scale less token will be available which means increase in value automatically base on this and also token can be charged for 1Mwat energy now it is charged with 1KWat.
Red's MWAT tokens as I think the best energy tokens on crypto market now. Franshise and passive income opportunity shows this project like great long term investment.