In case it wasn't clear from earlier photos or descriptions, the above photo shows how the back of the Belkin has two board, the filter board and a much larger UPS sinewave inverter board underneath. In the middle are the inverter transistors in a heatsink and a transformer.
The above is a closeup of one inductor and capacitor used in the line filter, and off to the side you can see the chokes that the incoming ground (!) and powerlines run through. Good to see that the power is filtered right at the input. But the convenience outlet on the front panel is not only not filtered it can reflect noise back into the unit, as I discovered by plugging a tensor lamp into it. Plugged in there, the lamp created huge noises on stereo when being switched on and off. However plugging lamp into outlet beneath power conditioner shows the conditioner provides nearly perfect filtering from the outside, there is only just barely detectable noise (ear up to speaker) switching lamp then. So my advice is (ironically) only to use the front outlet for temporary convenience purposes like using a tensor lamp or soldering iron.
Above is the heatsink for the inverter transistors. Is this adequate for providing 1000W power? I suppose it must be, though it looks like the above heatsinks are only good for 100-200W actual dissipation at high temperature. Probably the transistors operate in Class D switched digital or Class G rail switching (like Carver amps) for maximum efficiency. I believe one of the most highly touted regenerators, the PS Audio Power Plant Premier also uses Class D. With these classes, much smaller heatsinks are required than for Class AB or Class A.
Above is another picture showing complete filter board.
Above are two photos showing the internal layout. Fortunately the heat sinks are in a mostly empty area of the unit. The transformer is also quite nicely separated from everything else.
Above is a view of the heat sinks from the side of the battery. Notice that on the left side of heat sink there are two medium size electrolytic capacitor within about a quarter of an inch. Perhaps they needed to be that close for electrical reasons, but the heat from the heatsinks is likely to shorten the life of the capacitors if the inverter is run to hot on a daily basis. Somebody might buy this unit thinking they can now run exclusively on battery sourced power...charge during the day and then disconnect and play at night, etc., powering amplifier and everything for 30 minutes at a time. But I think the construction of this unit does not look adequate for that kind of heavy duty cycle usage, only for occasional use for mostly short durations. With that kind of low duty cycle usage, it can probably last as long as typical electronics, about 20 years before needing repair.
The above is a picture of my living room where the previous pictures were taken, with my stereo and TV in the background. Notice on the far right of my stereo you can see the blue screen of the Belkin I am currently using there. The new unit being photographed is intended for the kitchen stereo. I recently rearranged the stereo putting most components as close as possible to the power conditioner so I can use short power cords and a minimum number of additional power strips. I think keeping AC wires as short as possible is useful because it helps to keep the EMI noise level down.
I bought a few short power cords recently (1 foot, 2.5 foot, and 4 foot) hoping to improve the current arrangement in which generic 6 foot cords are coiled somewhat in the corner. But the new cords were not shielded, and I decided it was important to stick with shielded cords. So I have now found a source of short shielded power cords and have ordered them. I might also choose to upgrade particular cords, like the 3 foot cord that connects to the Belkin itself, to something super premium like Cardas. I've spent some time recently looking at the designs of nice quality (e.g. Belden) and audiophile grade (Audioquest, Cardas, Valhalla). I generally like the approaches taken and the materials used by George Cardas. I'm strongly skeptical that you can actually hear the difference between using $200-$1000 power cord from Cardas and a standard 14 gauge shielded cord in a double blind test. But it looks to me like the Cardas cords and speaker cables are designed and made about as well as can be. In both cases of low lumped impedances, the chief performance issue is self-inductance, and Cardas deals with that through elegant Litz wire designs. This is not fake snake oil, it is the real stuff, the only question is whether you actually need it or not. (But if you're an audiophile, you know how that question is answered.)