How about an inverter-genset... with a battery

So inverter-gensets have established themselves in the market. They have advantages like lower gas consumption and less noise when your load is light. They do this by throttling down to an idle, fewer revs = less gas used. All of this is nothing new to most people here.

I get the most out of my (non-inverter) genset by loading it up as much as possible when its running, others here do the same, because they operate most efficiently that way. You get more kW per gallon of gas/LPG or cubic foot of NG. This includes using a battery bank + inverter to time-shift some of that energy. While there is a 25% efficiency loss between the charger and inverter, its 50% cheaper per kW to charge the batteries when the genset is fully loaded vs. half-loaded or even less-loaded, so overall there is a 25% savings. Priuses (Prii?) do the same when they are parked but on and running things like the A/C. Start, recharge a little, turn off, repeat.

That got me thinking, why not take inverter-gensets one step farther and add a battery? You end up buying something the same size as a Honda inverter-genset but you must add a 100 amp-hour deep cycle battery. I'm operating under the assumption that under a light load there is a greater fuel savings running at full throttle for spurts vs. idle. It is entirely possible the opposite is true, but I doubt it or else hybrid cars would always idle instead of turn off. You would have the option of either selecting for best fuel economy (FE) or the quietest operation (QO). When in QO mode it would operate the same as current inverter-gensets, with the benefit of electric start even on smaller models. The battery wouldn't do much except handle brief surges so the engine could stay at idle. In FE mode it would run full-throttle for a while to recharge the battery then shut off for a while, and repeat, when it is lightly loaded. Under a full load it would operate like any genset on the market and run at full throttle, throttling back as the load drops. Maybe at 50% load it would begin cycling on-off, tests would have to determine where it makes sense.

If you remove the QO option so the genset is always loaded up you could even move to a diesel engine and decrease the fuel useage that much more.

Maybe there wouldn't be enough fuel savings to make the additional size and weight of lugging around a battery worth it (but I keep thinking about hybrid cars and believe the fuel savings would be worth it). Additional complexity means a bigger chance of something going wrong, and more maintenance. Your average Joe wants to pull his genset out, start it, and forget it until the tank runs dry - and this system would require a little more "fiddle factor". Things could be made easier by adding something like an Andersen connector so the user doesn't have to mess with thumb screws all the time. I see many reasons for big companies to not bother producing something like this even if the fuel savings is decent. Running at idle is "good enough", so that is what Honda will produce.

But for some segment of the market fuel economy is paramount and noise is secondary. Thoughts?