Electric Generators

Brooke Clarke 2001 - 2019

Mode of Operation
Generator Interlock Kit
Honda EU7000iS
Fuel Choice
Fuel Consumption
Honda Generator Codes

Mode of Operation


A classical AC generator determines the output frequency by regulating the RPM.  As the generator is loaded the RPM falls and the regulator opens and sends more fuel to the engine to speed it up.  Lower cost 60 Hz generators run at 3600 RPM and the better ones run at 1800 RPM.  Running at a slower speed translates to quieter and half the wear or twice the life.  The regulator mechanism to do this dates back to steam engine times and can be as simple as a fly ball governor (Wiki).


This is where the engine turns an alternator with AC output that varies in frequency with the engine speed.  The AC output is rectified into DC which in turn is converted back into AC at the desired output frequency which is typically 50 or 60 Hertz.  In this case when there's no load the engine is throttled down to an idle RPM and as the load increases the engine speed is raised to supply the needed power. 

Parallel Operation

It seems to be easier to connect the outputs of these generators in parallel so that they share the load.  This is very difficult to do with a classical generator where any slight electrical phase difference will cause them to fight each other.

Fuel Economy

Since the RPM of the engine depends on the power delivered the engine slows down for light loads thus greatly reducing fuel consumption.  This also lowers the noise.


The inverter mode makes for a more expensive generator, but I expect that's going to be paid back by the benefits listed above.

Generator Interlock Kit (less expense than full transfer switch and just as safe)

Sliding metal plate prevents main breaker and adjacent generator breaker from being on at same time.

YouTube: How to Connect a Full Size Portable Generator To Your House Safely - Storm Ready - using Honda EU7000iS Generator, burning 5 gal gas per day.
YouTube: How to Install a Generator Interlock Switch  - notice different style than above interlock switch.

Interlock Kit - carries various configurations to match entrance electrical panel as well as the Inlet Box and 30 or 50 Amp generator cable.

Honda EU7000iS

This Honda generator gets a lot of good reviews. Excellent fuel economy (ECO mode) and ability to parallel with other Honda "i" Inverter generators.
The ECO mode (turned on after starting and running for a few minutes) saves gas by allowing the engine to throttle down if less than full load.  This only will work with an inverter type system.  

The EU7000iS has fuel injection rather than a carburetor.  Since carburetor fouling from sitting gas is the number one problem starting after a year of sitting this is an excellent idea.
The solution to the problem for small gas engines with
carburetors is to keep the engine running until the gas tank is empty just prior to storing the engine.  If you store a gas engine with gasoline in the carburetor there's a good change you will plug some of the orifices and it will not start next year.

Fuel Choice

Gasoline contains varnish (coloring) and hydrocarbons that can cause it to go stale after sitting for many months or years.  This may lead to problems starting.

The solution to the problem for small gas engines with carburetors is to keep the engine running until the gas tank is empty just prior to storing the engine.  If you store a gas engine with gasoline in the carburetor there's a good change you will plug some of the orifices and it will not start next year.  Putting 1 ounce of Sea Foam per gallon of gas may stabilize the fuel.
YouTube: How to store gasoline & fuel long term - Stabilizer DIY for 1 week of Fuel - Sea Foam motor treatment - [1 oz/Gal] - Stabilizes gas & diesel fuels up to 2 years

 Propane does not have that problem, but as explained in the Fuel Consumption paragraph below, may take more gallons for a given number of kW hours.
Modern diesel also has additives that may degrade it's ability to be stored.

Wiki Gasoline gallon equivalent:  1 Gal Gasoline = 0.88 Gal Diesel #2 = 1.54 Gal Natural Gas = 1.25 Gal Propane = 33.4 kW hours of electricity

So let's see if there's data on fuel consumption for propane generators.
Champion - 8000-Watt Dual Fuel Generator - gasoline or propane - no on line fuel consumption data.

Fuel Consumption

2019: Thinking about house backup generator considering the lesson learned from the fires the past couple of years (2017 Redwood/Potter, 2018 Ranch & River) that the ionized air above a fire is conductive and will short out the AC power lines.  This blows a system wide fuse resulting in power loss.  Or . . .  if the firemen see that a fire is about to blow a fuse then notify PG&E and they shut down the grid.  In either case the power is out for a few hours.  But in cases where wooden power poles burn and the lines fall to the ground there will be no power for days.  If that happens then a generator that uses propane from a 250 gallon tank will require refilling from a truck, it is not something you can refill yourself.  Gasoline as a fuel is a poor choice for a standby generator because it goes bad when sitting for long periods of time.  The optimum fuel choice in this case seems to be diesel since you can go to any working gas station (might need to be out of the area) and get it in 5 gallon cans.

Diesel fuel consumption Gallons per hour & [Gallons per kW hour varies between 0.7 and 1.4 Gal/kWhr at full load]

No Load
Cummings Onan
RV QD 12500




Kubota GL7000

Kubota GL9000

DA7000SSA3 6

Note to get Gal of propane per kW hour multiply by 1.42.  So at full load a propane generator will need about 0.1 Gal Diesel/kWh or .142 Gal Propane.

Honda Generator Codes

The "i" suffix seems to indicate Inverter, as described for the EU. Quiet & efficient operation.  [EU1000i, EU2200i, EU3000i, EG2800i, EB2200i, EB2800i]
The "S" suffix seems to indicate the 10 second high power Starting capability for motors. [EM4000S, EM5000S, EM6500S] or maybe Self Start?
The "iS" suffix seems to be for both of these. [EU3000iS, EU7000iS]
The "c" suffix seems to be for CycloConverter technology [similar to inverter by there's no DC in between the input high frequency AC and the output low frequency AC]

EU Recreational

These make use of an AC generator running at whatever the engine speed needs to be to supply the load.  That AC is rectified into DC and drives an inverter running at 60 Hz in the U.S..
Very efficient and quiet.  Two generators can be connected in parallel with a special cable to double the capacity.  Typically only have 120 VAC and 12 VDC output, not 240 VAC.
EU1000i - 2019
EU2200i - 2019
EU3000i - 2019
EU3000iS - 2019
EU7000iS - 2019 (retail: $5,000, )

EG Home Backup & Construction

120/240 VAC outputs, HD frame.
EG2800i - 2019
EG4000 - 2019
EG5000 - 2019
EG5000CL - 2019 Home Depot  $1749
EG6500 - 2019

EM Emergency Home Backup

Electric starting, 10 second high power output to start motors, wheel and lifting kit, 120/240 VAC outputs
EM4000S - 2019
EM6500S - 2019

EB Commercial Industrial

Inverter technology similar to the EU series. GFCI and Wheel & Lift Kit.
EB2200i -  2019
EB2800i - 2019
EB3000c - 2019
EB4000 - 2019
EB5000 - 2019
EB10000 - 2019


Capstone MicroTurbine -
This company sells a 20 kW model with a stated efficiency of 27%, in versions for low and high pressure gas feed. The large fridge-sized cabinet of this system received the "Good Design" award from the Chicago Athenaeum Museum of Architecture and Design", the oldest industrial design prize in the world.
Elliott Energy Systems - Unison Alternators
Elliott is the only manufacturer to provide systems of different power output: in addition to 45 kW and 80 kW models, a 200 kW model is in the pipeline. The systems produced by the UK packager Bowman are also based on the Elliott microturbines.
Exide Technologies - GNB Technologies -

Foster Wheeler Corporation - for powering a city

GE Power Systems - GE Micro Gen -

Honda - Manes a number of generators that are much lighter than the competition.

CycloConverter Generators
2523090 Parallel Operation of Converters, Westinghouse, Sep 19, 1950, 307/47 - oldest patent with the word CycloConverter (named in this patent)
7952230 Cycloconverter generator, Honda, May 31, 2011, 307/47 - Honda model EB3000c

Honeywell Power Systems Inc.

Previously known as AlliedSignal, this is the only major turbine manufacturer engaged  in producing microturbine systems. Honeywell systems are sold under the name Parallon 75 and have a 75 kW output with 28% efficiency.
Hpower - Fuel Cells

Ingersol-Rand Energy Systems - micro turbine

International Fuel Cells -

K-tronik International Corp. -

Kohler - Generators -

Marathon Electric, Inc -

Turbec AB

Turbec is a Swedish company created in 1998 by Volvo and ABB to complete the development, and market, the 100 kW VT 100, previously developed by Volvo Aero turbines. The company claims an efficiency of 30%. This is the only microturbine produced which from the start has had a thermal recuperation system for cogeneration applications.


6707170 Inverter type generator, Yamaha Motor Power Products Co Ltd, 2004-03-16 - uses two alternators, one for normal loads and another for high loads.
8232777 Inverter generator, Honda Motor Co Ltd, Priority: 2008-07-25, Pub: 2012-07-31 - includes harmonic distortion minimization to give clean sine wave output
9077207 Parallel running control apparatus for inverter generators, Honda Motor Co Ltd, Priority: 2011-05-17, Pub: 2015-07-07 - 3 phase, 4 wire system.
9086044 Start control apparatus for engine generator, Honda Motor Co Ltd, Priority: 2011-05-17, Pub: 2015-07-21 - for starting piston engine; uses more starter current just prior to TDC.


MEP-25A 28VDC Military Generator (Gasoline) - to power the GRC-206 Pacer Speak radio system
Weeden-El-Mtr  Weeden DC Electro0magnetic Machine
ArCo Demonstration AC DC Generator
Permanent Magnet DC Motors, Testing Small DC PM Motors - these also work as DC generators


American Power Systems -
DOE - Summary of Micro Turbine Technology.pdf - Advanced Micro Turbine ystems.pdf -

Makelim Power Systems is Stockton, CA Kohler dealer

Natural Gas, Italy - Microturbines for cogeneration -
SMP Electric - Microturbine -

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