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I would really think of putting in a under counter LED solution or some dimmer LED lights. Dimming 50% most light sonly saves you about 10% of power. Where as you put in a LED light or strip it saves you 95% of the power. When we remodel rooms now as a course of action we alwas put in a "night light" one led bulb or strip or whetever to keep on at night for walkthrough traffic.
Those early rheostat dimmers were really early - I have never seen them in use in residences; I built myself a few triac dimmers in the early sixties. I agree with "stusviews" that they wasted a lot of power (I saw them to dim flood lights in theaters). Unfortunately, the math is wrong. If set in the middle, the rheostat would consume as much power as the load and the total load would be 50% of the load with no dimming. A 100W light dimmed to 50% with a rheostat would consume 25W and the rheostat 25W. The math applies equally even if the load changes with temperature - then the "middle" is no longer 50% but some other ratio that could be manually tweaked to 50%. Triacs or back-to-back thyristors (SCRs) waste energy as heat only when they have fired and conduct current to the load. There is a drop of about 1.6V across the triac (or back-to-back SCR). So let's say we have turned on a 60W lamp supplied by 120V at full brightness. The lamp draws 0.5A and this causes the triac to dissipate at 1.6V voltage drop 0.8W as heat. The lamp now actually gets only 118.4V but that's a negligible error). If we dim the light, conduction angle will decrease, so at 50% dimming (assuming that the voltage, conduction angle and brightness have linear relationship) the heat dissipation will be 0.4W. I wouldn't assign triacs just to low cost designs. It all depends how the load system and especially its EMP characteristics are designed. There are triacs rated for 800V/40A, that means they can handle loads up to 4.8 kW at 120V. That's a lot of load for residential use - for an aircraft system where a 60kW load had to be handled I had to go with back-to-back "puk" thyristors. But then there were triggering issues I wouldn't have had with a triac.
LEDs for sure saves a lot of energy. I read somewhere very recently that with electric bulbs only around 40% of the power consumed is converted into light .. the rest is dissipated as heat. so you can imagine the amount of energy wasted. Even windows installation is critical to reducing energy consumption.