Off Grid Home Forums Technical Discussion Gas Generator Comparison Re: Gas Generator Comparison


There are two waya to reduce fuel burn with a generator. One of them is the Honda version where the speed varies with load. This is often called VST for variable speed technology. The other approach is to configure the system so the engine is fully loaded so it runs at optimum BSFC point as indicated by engine manufacturers curves.

You can see that the BSFC curve rises as engine speed slows down. What this tells you is that maximum fuel efficiency occurs when the engine runs faster at a point that typically falls on the peak of the torgue curve. In most small engines such as is used for gensets this is around 2400 RPM especially if the engine maxes out at 3000 RPM. Some manufacturers chose to run an AC genset at 3600 RPM by shortening the stroke. It means they develop the required torque /HP to deliver the rated watts output at 3600 RPM instead of 1800 RPM. It makes for a smaller, lighter engine but. . . . The downside is reduced service life between rebuild interval due to higher wear factor.

If you are going to run an AC output generator select a charger that can absorb 80% of the max output. Dedicate the genset to charging the battery at maximum rate. The alternative is A DC generator which can more easily be adapted to VST. Balmar introduced the VST concept some 15 years ago. Since then it has been copied by several manufacturers including Honda.

There are several propane conversion companies marketing adaptor kits. Tell them which engine model you have and they will give you the exact metered kit for it. They offer both dual fuel or straight non reversible conversion kits. I can’t look it up while doing this message or it gets dumped. Just google “propane conversion kits” to find them.