efficency and inverter generators

The highest RPM is faster, because it lets them use a smaller cc engine, just turn it faster 4300 vs 3600 of the larger engine

Same is true for the CPE 2000 inverter which uses an even smaller displacement cylinder

Same thing automotive MFG have been doing for a number of years

Wayne Dohnal wrote:
1,600 watt load: Run time 2.97 hours/gallon. 4.75 kWh/gallon, RPM = 4,300
465 watt load: Run time 8.92 hours/gallon. 4.15 kWh/gallon, RPM = 3060
555 watt load: Run time 8.06 hours/gallon. 4.47 kWh/gallon, RPM = 3150

Those are interesting RPM numbers for Honda inverter generators.

My two small non-inverter portable Hondas of course turn at a constant 3600 RPM. I wonder why Honda has to spin their inverter models so much above 3600 RPM to get maximum power output?

If Honda would have topped their variable RPM inverter generator models out at 3600 RPM, like their earlier non-inverter models run constantly at, then at their maximum power RPM speeds their noise specs could have been lower.

For example one of my 3600 RPM Honda generators runs at only 54dB all the time, even when putting out it's 550 watt maximum power.

If the Honda inverter generators could have been designed to deliver their top power at a maximum of only 3600 RPM, then they could have been really quiet all the time. :h

Howzabout tossing in a 30VA load just for chuckles?

BurbMan wrote:

Wayne Dohnal wrote:
With all those disclaimers, the general result was that the load level didn't make a whole lot of difference in fuel consumption.

1,600 watt load: Run time 2.97 hours/gallon. 4.75 kWh/gallon, RPM = 4,300
465 watt load: Run time 8.92 hours/gallon. 4.15 kWh/gallon, RPM = 3060
555 watt load: Run time 8.06 hours/gallon. 4.47 kWh/gallon, RPM = 3150

What am I missing here....yes, the EFFICIENCY stays pretty constant at 4.xx kWh/gal, but the CONSUMPTION varies with the load according to your results, ie, the 1600w load uses 3x the fuel compared to the 465 watt load.

I don't think you're missing anything. The question was how to get the most watts per gallon; loaded or not. Seems that it doesn't make much difference. Efficiency is more or less constant, you'll use fuel in direct relationship to the wattage you use.

Regards,
Doug

Wayne Dohnal wrote:
With all those disclaimers, the general result was that the load level didn't make a whole lot of difference in fuel consumption.

1,600 watt load: Run time 2.97 hours/gallon. 4.75 kWh/gallon, RPM = 4,300
465 watt load: Run time 8.92 hours/gallon. 4.15 kWh/gallon, RPM = 3060
555 watt load: Run time 8.06 hours/gallon. 4.47 kWh/gallon, RPM = 3150

What am I missing here....yes, the EFFICIENCY stays pretty constant at 4.xx kWh/gal, but the CONSUMPTION varies with the load according to your results, ie, the 1600w load uses 3x the fuel compared to the 465 watt load.

Commercial generators use pounds of fuel per hour (Decimal fractions) per kWh.

See if Honda can furnish an efficiency chart it's called PERCENTAGE LOAD EFFICIENCY. You'll have to write to the authorized North America importer.

In a critical economy situation high in the Sierras (11,200 ft altitude) I had to engineer the best compromise between 600 watts and 9 KW load. A Perkins turbo diesel was selected, but it could not be direct drive to be efficient. I had to underdrive a twelve turn two bearing AC alternator to get good results. This was long before the advent of inverters.

I used a division-marked gallon jug, inverted feeding the genset to calibrate my efficiency charts. On a little Honda, a quart jar (in liters too) would have better resolution. Combine the measurement device with a clock and a Kill-A-Watt set to kWh and you'll have a pretty fair test bench.

Hi,

I get 7 hours 55 minutes when I'm running mine "flat out". I.E. running the fridge (325 watts), air conditioner (1200 watts), and converter (max 725 watts).

Interesting that a on a 1500 watt load fuel only lasts 8 hours.

That implies I may as well grab as many watts as I can while the air conditioner is running.

I can't run the water heater (1200 watts), the air, the converter and the fridge, at least not in the Rocky Mountains. Mind you, at that time the generator had only 20 hours of run time on it.

I also use the inverter to run the water heater when I'm needing to air condition. Sounds as if that is a good approach.

From the website: " It will run up to 19 hours at ¼ rated load on a tank of gas. "

As a rule of thumb, I've found generators tend to be most efficient at half a load.

With my Yamaha iSE (similar to the SEB but sans battery): If I run just the 55 amp excuse for a converter, I can get 15-20 hours from one tank of gas on econ throttle. If I use my 15,000 watt A/C, I end up with about eight hours of generator life.

With more than a 1/2 load, econ mode is pointless, so I click it off.

So, those are two data points... 550 watts for 15-20 hours, 1500 watts for about 8 hours. Not perfectly linear, and not really that accurate, but just rough guesstimates of what I end up using. Were I to say what gives the best bang for the amount of fuel used, I'd go with the 1500 watts, which seems to be at the best performance point.

At FULL IDLE and no load any fuel powered generator is running at zero percent (No power delivered, still burning fuel)

At some point it peaks, With inverter generators this is fairly fast,, From there on increasing load will increase fuel consumption in a near linear fashion, that is double load, double consumption.

With traditional generators.. I varies depending on who designed and tuned the thing.