Power consumption is less of an issue, considering how "overpowered" 055 is, in any case a 300kW laser is not going add a lot more burden to a 4X28MW ship.
Space though is an issue. IMO only when lasers are considered to be superior to CIWS will we start to see lasers on board replacing things like 1130.
Another possibility is perhaps redesigning the integrated mast to leave room for lasers system, this would be the optimal solution giving laser turret the topmost position with clear los and better range against sea skimmers
I think you may have confused ship propulsion system with ship electrical generation and usage.
The 055 DDGs use COGAG propulsion system, where 4x CGT-25M gas turbine engines provide ~27MW each (or ~108MW total) to propel the ship forward in water during full speed dash (30+ knots).
However, these gas turbine engines are only meant for the ship's propulsion, and is not connected to the shipboard electrical grid that powers everything else (i.e. radars, sensors, computing systems, weaponry etc etc). The latter is powered by a separate, yet-to-be-publicized number and models of diesel and/or gas turbine engines.
Only in the case of IEPS configuration would the CGT-25Ms be responsible for both the propulsion and electrical grid systems of the ship, of which the 055 DDGs are clearly not the case.
Moreover, a "300-kW laser CIWS" does not mean that only 300kW of power supply is needed to power said platform. The actual required power supply is actually much greater, considering that there are plenty of parts of the platform that would require power as well (with the cooling functions being one of the most prominent), as per calculations by the US Navy on the power and effectiveness of DEW systems some years ago (posted by SOYO on Weibo):
As can be seen, a 300-kW laser CIWS actually requires a 1.2MW power supply.
Last but not least - Laser CIWS is only meant to be complementary to the existing gun-based Type 1130 CIWS and missile-based HHQ-10 CIWS, and not to supersede, let alone replace them.
