Hawaii has some of the highest commercial electricity rates in the country, which changes the maths on lighting retrofits considerably. Payback periods that look marginal on the mainland are often short here.
Where the payback is fastest
Warehouse and high bay lighting. Replacing 400 watt metal halide fixtures that run long hours with 150 watt LED high bays cuts both consumption and the cooling load they were adding to the space.
Exterior and parking lighting that runs every night. Long hours plus high wattage is exactly the combination that pays back quickly.
Refrigerated display lighting in retail and grocery, where you save the lighting energy and the cooling energy spent removing that heat.
Where it is slower
Spaces with short operating hours, back of house areas, and anywhere already running efficient fluorescent tubes on electronic ballasts. The saving per fixture is smaller and the labour per fixture is the same.
That does not make it wrong, it just means it should be bundled with the fast-payback areas rather than done on its own.
Retrofit or replace
Ballast-bypass tube retrofits are cheap and quick but leave you with a fixture designed for a different light source. Full fixture replacement costs more per unit and gives better distribution, better control and a longer warranty.
For high bays and exterior lighting we almost always recommend replacement. For office troffers, a retrofit kit is often the sensible middle path.
Controls are where the second saving is
Occupancy sensors in storerooms, restrooms and back of house. Daylight harvesting near glazing. Scheduling for exterior and signage. These routinely add another meaningful reduction on top of the lamp change, and they cost very little when installed during the same visit.
Doing it without closing
We schedule commercial lighting work overnight or in staged zones so the business trades normally. For retail and restaurants that is not a convenience, it is the only way the project is affordable, because lost trading hours cost more than the fixtures.