Standby Generator Efficiency Testing

[ChrisOlson]

Due to the claims made on inverter generators and all the marketing hype surrounding how supposedly fuel efficient they are, a friend and I tested one yesterday.  It was a Yamaha, owned by him.  We tested it against an ancient Generac GP3250 that has over 4,000 hours on it.  The Generac is not in real good shape anymore, but I put new valve guides in it so it doesn't smoke (the valve guides were really bad).  But the valves and seats in the head are shot.  It was the only unit I had in the same size class that we could test against the high-tech Yamaha.

Amazingly, it kicked the Yamaha's a$$ for efficiency.  In the mean time I got hold of a Yanmar YDG3700 diesel to test, and a Honda EM4000 that I can add to the data after I test it.  I'm trying to find somebody that's got a Honda inverter gen I can test, but so far haven't found anybody.  I think I can get a rental unit to test though.

We ran the generators on a measured 10 ounces of premium 91 octane pump gas with no ethanol in it, and measured the run time on that 10 ounces of fuel with various loads.  We also did some surge testing, but it wasn't even worth recording any data on that.  It would take 2 or 3 of those Yamaha inverter gens to match the Generac for raw surge power.

The results of the test we did yesterday are below



Edit to add some info:
The claims on the small inverter gens is that they're more fuel efficient, and that's why we tested these two units.  The claims are false, at least in the case of the Yamaha.  What sparked my interest in testing them was that after working as a mechanical engineer in the engine business for close to 30 years I know that an Otto Cycle engine is least efficient at low mean piston speeds.  They use the so-called "Eco Throttle" on the inverter gens to idle them down, and this is supposed to save fuel.

From our test, it appears that it only saves fuel at no, or very light, loads.  It was interesting to see in the test, that the efficiency of the Yamaha continued to increase with loading and gains in rpm.  But it cannot keep up to the old Generac because the losses in the SCR's and inverter electronics of the Yamaha outweigh engine efficiency gains as the load is applied.

The old Generac, OTOH, gained significantly in engine efficiency as the load came up (it's a constant 3,600 rpm generator).  But with no losses in electronics, it's overall efficiency is much greater than the inverter unit.

These are both about 3,000 watt generators, and only if you had loads that are below about 25% of rated power would the inverter unit come out on top.  And then it's not by very much.

The test also shows the importance of sizing your standby generator for off-grid use when it runs an inverter charger to charge batteries.  When it comes online it should be running at as close to full load as possible to get the most kWh from every gallon of fuel.  This is not possible for grid connected standby generators - they have to run at 50% load continuous to have reserve capacity to start heavy surge loads.  For off-grid that's not an issue as the inverter takes care of that even when the gen is running - at least my inverters do.
--
Chris

[rossw]

The results of the test we did yesterday are below

How can you say "Output: 744.2 watts", yet 0.744 kWh if it only ran for 24.2 minutes??

Surely that'd be 0.300 kWh ??
This inconsistency continues through all recordings.

[ChrisOlson]

Hi Ross,

The calculations done in the spreadsheet are arrived at based on the run time on 10 ounces of fuel, then that is converted to BTU or kW input in one hour.  The load was measured to determine watts, and the kWh column is the amount of actual power that would delivered to the load in one hour.  The efficiency is calculated by taking the difference between the input in BTU or kWh, vs output.
--
Chris

[rossw]

Hi Ross,

The calculations done in the spreadsheet are arrived at based on the run time on 10 ounces of fuel, then that is converted to BTU or kW input in one hour. 

OK, that wasn't clear when I looked.

In the light of the additional information, might I respectfully suggest that displaying column 'I' is unnecessary and misleading, drop it entirely and do the conversion from measured instantaneous load (watts) to kWh in the efficiency calculation.

[ghurd]

"From our test, it appears that it only saves fuel at no, or very light, loads"

That was my personal understanding of the entire concept.

When I (and most people I know) run a generator, it runs for 30 minutes screaming its head off, just to power a small circular saw for long enough to cut a couple 2x4s.

I see people in RVs run a giant genny to power a 60W 32" LED TV, but I just thought they were.... uh... "uninformed".
G-

[ChrisOlson]

There's no doubt the little Yamaha is a nice generator.  It has super clean output and will run HDTV's and other sensitive electronics that would have problems on the output of the Generac.  It's very quiet too.  That old Generac sounds like some sort of hammer press running compared to the Yamaha   

We just got interested in whether or not the fuel efficiency claims are true or not.  It appears that they CAN be if the load is light enough.  But the generator is still terribly inefficient at light loads.  And it looks to me like if you buy an inverter gen to run light loads, you'd probably be better off to just buy a smaller conventional gen to run those loads, assuming you don't need the super clean output of the inverter.

We got hold of a Honda EM4000, which is a conventional generator but it has an "Eco Throttle" on it, and it's a very quiet running generator.  We also got a Yanmar diesel - YDG3700 that we're going to test.  The Yanmar is not as quiet as the Honda, but we already had it running and tested it for surge power - and you'd swear you got a 5 kW unit because it will start stuff the Honda won't.  That little Yanmar diesel is a pretty impressive generator.

We're going to test the Yanmar next.  Yanmar claims these little diesels are supposed to be more efficient than a gas unit.  So we're going to test it with the same setup and see if it's true 
--
Chris

[bob g]

Chris

come back and tell me when you have tested and returned in the 9-10kw/hr range per gallon of pump diesel

the whole idea behind the inverter/generator thing comes down to cleaner power via the inverter, and the ability to run at low speeds with less noise when the load either is non existent or very low.

these little units really shine in motorhome use,  other places where you don't need significant amounts of power continuously, rather you need very small amounts of power over a run time with the ability to ramp up to cover heavier loads at will.

your test really is an example of apples to oranges, don't you think?

i would expect an inverter generator to be less efficient than a standard generator at near
peak load, the standard does not have the additional losses of the inverter section no matter how low those losses might be. however i would expect that the inverter generator to be significantly more efficient than the standard genset "if" a test is designed to illustrate the inverter gensets strong point of being able to deliver higher quality power over its range, be able to do so with lower noise and provide for low amounts of power for protracted periods of time.

one thing i know from experience is this, an inverter generator "can" kick the snot out of any standard generator in overall efficiency, surge capacity, noise reduction "if" it is designed and built to do so, however it won't be cheaper than a standard.


bob g

[taylorp035]

First off, I would like to say that it is awesome to see someone doing a test like this

I wouldn't say that a 0.2% difference is statistically different in efficiencies, but it's good that you are using 10 ounces of fuel. 

The run time is fairly long too, so any irregularities with block temperature and AFR should average out between the two.


One reason why the yamaha could be dropping in efficiency could be that you have gotten past the point where the AFR can be held at its normal level (~13:1).  I bet if you test the Generac at something a bit higher, like 3000 watts, you would see the efficiency drop too.  Last week during my engine testing of our supermileage 3.5 hp briggs engine, we hit 2 hp at 16:1 and we could not go any higher (AFR or hp).  At power levels above 2 hp, the AFR needed to be lower to get more power.

Our analysis of our briggs engine has shown that max efficiency doesn't change much with power levels, so its fairly steady between 1 and 2 hp.


My dyno tests I'm doing for my car peak at ~13% efficiency at the electrical output, and that's before you convert it to AC.  I'm also betting that your generators aren't running at 16:1 AFR either  .  I always wondered if a small 500 or 1000 watt generator would be more efficient than an L-head briggs was, now you answered my question.

[oztules]

"your test really is an example of apples to oranges, don't you think?"...... no I think it was a test over 4 different power ranges of two similar power range machines.

"i would expect an inverter generator to be less efficient than a standard generator at near peak load," ... read the results, you won't have to guess any more.

"however i would expect that the inverter generator to be significantly more efficient than the standard genset "if" a test is designed to illustrate the inverter gensets strong point........"      .......yes we can prove anything we want if we really want to ... ask an economist, or environmentalist.

"one thing i know from experience is this, an inverter generator "can" kick the snot out of any standard generator in overall efficiency, surge capacity, noise reduction "if" it is designed and built to do so"..... what on earth does that mean?  .... so what, I can build a non-standard generator to do what ever I want...cleaner power, quieter, better surge, no electronics.... ........ but  that wasn't the test that was done.

This was a user diary where a man tested two machines of similar range in a real world test for his circumstances.... you have to live with the results I'm afraid.




................oztules

[Norm]

"From our test, it appears that it only saves fuel at no, or very light, loads"

That was my personal understanding of the entire concept.

When I (and most people I know) run a generator, it runs for 30 minutes screaming its head off, just to power a small circular saw for long enough to cut a couple 2x4s.

I see people in RVs run a giant genny to power a 60W 32" LED TV, but I just thought they were.... uh... "uninformed".
G-

....And to think about 70 years ago people like my Dad used to use a really sharp hand saw....no square or guage
and saw a perfectly square cut on a 2x4 in about 15 ...20 seconds? and it didn't impress me....then 
Norm.

[tanner0441]

Hi

I have one of the inverter generators on my motor home. It is a Chinese copy of the 2 KW Honda, why did I buy it when I have a 2.5 KW portable generator?

1 It is smaller and lighter. I can lift it in and out of the cupboard with one hand.
2 It is much quieter.
3 For the type of use I give it, it is better, it runs all the facilities in the vehicle, with the intelligent throttle, (seems everything is intelligent but me these days) it sits quietly at a fast idle, when I fire the kettle, microwave, or induction hob up. It blows a little puff of black smoke out and revs its nuts off, when the load goes off the revs drop back.

If I use it to work for its living with say a fan heater I switch the throttle to manual, that cute little puff of black smoke is unburned fuel, and is sooting my plug up.
It's a pity your not closer Chris you could borrow this one to play with. It would be interesting to see how a cheapy compares to a branded one.

One thing I do like is, the output waveform. I couldn't resist putting the scope on it. The waveform is clean, no obvious harmonics or wobbly phase angles, and no AVR transients, the overshoot and frequency drift from no load to full load is insignificant.

I have used it for a full weekend on only one occasion, and it used well under a tank full and ran about four hours a day over three days, At full load the tank is rated at five hours.

When I first had it I ran it into a 2 KW fan heater for a few hours to try it while it still had a guarantee on it.  It does what it said on the can.

Brian.

[ChrisOlson]

We tested the little Yanmar today and this is the results we got from it:



With the 750 watt element hooked up for a load, the thing ran, and ran, and ran - and it didn't look like it was using any fuel out of our graduated container.  It took it almost 40 minutes to use 10 ounces of fuel with a 750 watt load.

It beats both gas units across the board for efficiency.

And as a side note, that Yanmar is a NICE generator.  It runs smooth, it's got a good governor and doesn't surge.  It doesn't smoke, it's relatively quiet, and it starts with the engine bone cold with one tug on the starter rope.  Just a little puff of smoke when it starts, and then it runs clean.  I wouldn't mind having one of these.

Interesting to see  - the BTU content of #2 diesel fuel is higher than gasoline.  But the BTU input of the Yanmar is less than either of the gasoline units at the same load.  It's a diesel - it's more thermally efficient than the spark ignition engines.  And it beats the pants off the inverter gen for efficiency even at the very light 750 watt load.

The Honda is next.
--
Chris

[tanner0441]

Hi Chris.

I used to fit pairs of Yanmar engines in some of the boats I worked on and it literally was a case of fit and forget, we used the four cyl. 250 HP ones. I did fit a few six cyl models and at idle you could balance one of our pound coins on edge on the rocker cover and it would just turn gently.

All the Yanmar generators I fitted were electric start even the single cylinder models, the air cooled ones had a water cooled fin block in and the cooling air was circulated through this and round and round inside the silencer cover, the exhaust had water introduced just after the riser to shut the pop pop up from the exhaust.

The one problem we did have with the 4 cyl engines was if the sea water strainers became blocked they quickly boiled of the cooling water and melted the exhaust manifold through into the inlet manifold, it was a single aluminium casting. It was only a couple of hours to replace the manifold but the customers visibly paled when you gave them the bill................
All the exhausts on marine engines have water introduced to cool and silence the exhaust.

Brian

[bob g]

Oz:

my point about the test being apples to apples, instead of apples to oranges
in that you need to design a test that  fairly represents what the inverter generator
is designed to do.

you surely wouldn't take a ferrari and pair it with a john deere, connect it to a plow
and see how the two compare out in a field, would you?

conversely you wouldn't put the john deere on a road course and expect it to compete with the ferrari, would you?

comparing a standard generator to an inverter/generator  using only the criteria typically used for the standard generator just isn't any more fair than comparing the standard against the inverter/generator using the criteria that the inverter/generator is designed to run under.

it just isn't an apples to apples test.

unless your only concern is how does one compare against the other in a heads up test
at some fixed load value, in which case the standard should outperform the inverter/generator in fuel consumption per kw/hr in most cases, at least when comparing engines of similar size, type, etc.  At a fixed and more or less continuous load, there is no reason for an inverter/generator design, and i highly doubt that yamaha or any other manufacture of good standing would advertize anything differently.

for what they are designed for there is little doubt that the inverter/generator will do the job using less fuel, while making less noise, and probably last longer in the process.

that is the point i was trying to make.

bob g

[ChrisOlson]

Bob,

While much of what you say is true, I think the test is fair.  We found some heater elements to use for dummy loads, as we do not have an infinitely variable AC loading device.

At the lightest load, which is a 750 watt automotive block heater, the inverter gen did beat the Generac.  But it didn't beat the Yanmar.

We decided to try the test because of the manufacturer claims that they save fuel.  Right here on Honda's page, for instance, they make the claim that it saves fuel and they even got a little graph there that shows it:
http://www.hondapowerequipment.com/products/generators/content.aspx?asset=gg_inverteradvantage

But is it true, or is it just marketing?  It certainly sounds logical.  But where they say, quote, "Because the engine does not have to run at full speed constantly, Eco- Throttle reduces fuel consumption by up to 40%." is totally false in the case of the Yamaha unit we tested against a conventional generator of the same size class.  And just to be sure, Yamaha also makes a claim of greater fuel efficiency:
http://www.yamaha-motor.com/outdoor/products/modelfeatures/444/0/features.aspx

My friend is coming back over tomorrow and we're going to test the Honda to see how it fares.  And then we're going to try another test with the Yamaha vs the Generac with powering two of the kitchen circuits in our house for one day with each one and measure how much fuel they burn doing it.  The loads on the kitchen test will range from running the 'fridge, lights, microwave oven, toaster, coffee maker and what ever other small appliances my wife pulls out and uses.

My gut feeling is that the manufacturer claims on fuel economy are false across the board.  They're selling these things like hotcakes because they're small, portable, quiet, etc..  And they have a lot of good attributes.  But saving fuel isn't one of them.  If they'd quantify the claims by saying, "at loads less than 25% the Eco Throttle CAN save fuel over a conventional generator", that would be different.  But I think there's a heap of marketing involved here and marketing teams tend to bend facts.
--
Chris

[bob g]

Chris

fair points all...

the kubota being a diesel is going to be very hard for any gas engine to beat, at least in this class (3kwatt)

as for marketing, i would agree that they take (how shall we say?) artistic license? and play a bit loose with the facts, however if they state up to 40% fuel savings, my bet is there is some condition where this might be true.

my thinking is the reality might be somewhere around 10% would be the reality for most folks under conditions favorable to inverter generator operation.

even a 5% decrease in fuel consumption is something to crow about in my book.

look forward to seeing how things work out in testing for you.

bob g

[ChrisOlson]

as for marketing, i would agree that they take (how shall we say?) artistic license? and play a bit loose with the facts, however if they state up to 40% fuel savings, my bet is there is some condition where this might be true.

Oh, I'm sure there is.  Start up your generator and plug in a light with a 13 watt CF bulb in it as the only load on the gen.  That might do the trick.

But the marketing people tend to use methods of portraying this to make the consumer believe that the generator uses 40% less fuel than a conventional one.  And since nobody actually checks it, or compares it, the consumer BELIEVES it uses 40% less fuel just because it's so quiet and little.

There's kind of an old adage in the engineering world - "The best engineered products rarely succeed in the marketplace.  The best marketed ones do".
--
Chris

[ChrisOlson]

This is what we got with the Honda EM4000SX.  It's not the worst of the bunch, but it trails well behind the Generac on fuel efficiency.  None of them can beat the Yanmar.

I think the Honda's big 270cc engine hurts it on fuel economy.  The Generac has a 206cc engine with a higher compression ratio.  The Honda does put out very impressive stable voltage and frequency with its electronic governor.



--
Chris

[ghurd]

the whole idea behind the inverter/generator thing comes down to cleaner power via the inverter, and the ability to run at low speeds with less noise when the load either is non existent or very low.

Bob,
That's exactly what I was talking about WAY back via PM/email.
The electrickery works.  Most of the parts have been aquired.  Waiting for time to small square holes over large round pegs. 
G-

[bob g]

Ghurd:

sorry i had forgotten that interchange, guess it comes with age?



at least in my testing and development an inverter generator can compete very favorably
with a standard generator, most especially when used in a typical offgrid home environment where one has all the conservation measures in place and has his head in the game on how to do the equivalent of "hyper-mileing" his/her system.

i will state this much, it took a considerable amount of research/development and testing
(with all the problems associated with accurately measuring input and outputs) to finally get to parity and finally exceed the efficiency by 5 percentage points.  (inverter genset vs standard genset)

that of course is with a diesel engine as the prime mover.

i can't imagine how they figure a 40% reduction in fuel consumption for a gasoline engine driven inverter/generator unless the test is severely skewed to favor the inverter
genset?  (which is not to say that the inverter genset can't be more efficient, it just has to be run under certain guidelines to attain any gains in efficiency)

where "real" gains in efficiency come into there own is when you harvest and actually
"use" the waste heats available from the prime mover to offset things like domestic water heating, space heating, and if you are really good, refrigeration.  (cogeneration and trigeneration, "micro" in our case)

when you get to that point, you can start to make electricity competitively with the power company, or certainly very close to parity with the utility company.

guess this is something i am passionate about?



bob g

[rossw]

where "real" gains in efficiency come into there own is when you harvest and actually  "use" the waste heats available from the prime mover to offset things like domestic water heating, space heating, and if you are really good, refrigeration.  (cogeneration and trigeneration, "micro" in our case)

when you get to that point, you can start to make electricity competitively with the power company, or certainly very close to parity with the utility company.

When we found we couldn't (practically) get the grid the last 245 metres to our new place and HAD to roll our own, you wouldn't believe the amount of bashing my head against brick walls I had to endure trying to buy a cogen unit.

ONE company in Australia had one that they admitted to - made a great song and dance about. But when push came to shove, there was no way they would sell one. They were another one (I think) who only ever did enough work to get a sizable grant, then never did anything with it.

I spent ages trying to buy one from a company in Germany. They refused to sell their small units to Australia because they required maintenance every thousand hours of operation, and didn't have anyone in Australia to do it. Nobody in the USA would sell one at a price that was even in the same order of magnitude that I could get a bank loan for - and double it once you added freight. They also seemed to think they'd have to send engineer(s) to install/commission.

Spent 8 months trying to get ANYTHING better than an off-the-shelf air-cooled clunker.

In the end, I had to make it basically from scratch using a car engine... runs on propane but at least I scavange most of the heat out of the exhaust and block which provides heating and domestic hot water, and makes the inefficient conversion from propane->electricity bearable.

[ChrisOlson]

Nobody in the USA would sell one at a price that was even in the same order of magnitude that I could get a bank loan for - and double it once you added freight.

Ross, I know that one US-based company - Cummins (who I used to work for) - builds turn-key units as small as 30 kW.  And Cummins South Pacific, I believe, has at least four locations in Australia and one or two in New Zealand.  The Cummins units are all diesel, which may not work in your area depending on available fuel supplies and costs, however.  If LP is available and diesel is not, then obviously a diesel cogen unit will not work.
--
Chris

[rossw]

Ross, I know that one US-based company - Cummins (who I used to work for) - builds turn-key units as small as 30 kW.  And Cummins South Pacific, I believe, has at least four locations in Australia and one or two in New Zealand.  The Cummins units are all diesel, which may not work in your area depending on available fuel supplies and costs, however.  If LP is available and diesel is not, then obviously a diesel cogen unit will not work.

Yeah, that's the rub.  30kW !

Remember how you poo-hooed me for my "vastly overkill" 48V system, and "waste of money" pure-sine inverter etc - well, I only wanted a 5kW CHP unit.
I ended up building mine with a 14KVA 3-phase 1500 RPM machine, rewired to double-delta for a decent single-phase output at 8kW, which is plenty.

I can't touch diesel - after spending many years working on/with/in automotive, military and racing test, calibration, diagnostic and measuring systems, I ended up with such a case of petroleum intolerance that even now, almost 20 years later, I get itchy red whelts just from the fumes filling the car and need to apply cortisone, I can't use ordinary soap, or ointments that have petroleum jelly as a base, or most detergents etc.

[ChrisOlson]

well, I only wanted a 5kW CHP unit.

Ah - I wasn't sure what size we were talking about.

Seems to me that I've seen little Kubota cogen units about that size.  They're popular on semi rigs in place of the old "Hot Box".  I can't recall that I've ever seen a commercially built LP unit that size though in this country.
--
Chris

[rossw]

Seems to me that I've seen little Kubota cogen units about that size.  They're popular on semi rigs in place of the old "Hot Box".  I can't recall that I've ever seen a commercially built LP unit that size though in this country.

I couldn't find (and still can't) any Kubota cogen units. I can find 3rd-party assemblies of a Kubota engine in a cogen configuration, but just because it has a kubota engine doesn't make it a kubota CHP, if you know what I mean!

Seriously, I'm glad I built this thing, it's made me much more aware of exactly what I want in a commercial unit - but I doubt there will ever be one quite like I want!

Mine was also built with a 5-year life expectancy. Back when I made it, fuel-cell technology was really going places. Many people had ceramic and PEM based systems nearing market phase, several expecting to be on the market in 2-3 years. I figured that 2-3 more after that and they'd have the bugs ironed out and prices dropping.

Sadly, it looks like human greed stepped in about then, development stalled, there still isn't a working, affordable, practical unit I can buy or make.

My decision to build using a robust, solid mid-sized car engine, and a solid, industrial alternator, has proven to be a good one though, as the genset still hums along.
It's been in service now for 6 1/2 years. The engine had about 100,000km on the clock when I got it, and I've added the equivalent of about 600,000 more since then (based on hours run and RPM). It isn't using any more oil than it did when I first started. It doesn't sound much different. It's had virtually no maintenance apart from replacing the oil and filter every 400hrs or so, replace the plugs every couple of thousand hours, and it blew the ignition module 4 or 5 years back. (Not a repairable item - all potted up, fits in the bottom of the dizzy). At least I was able to talk them down in price a bit (check the invoice behind it! "Suggested Retail" is what the average mug would be paying, "Unit price" is what I had to fork over)

[ChrisOlson]

Well, yes I know what you're talking about.  The units I have seen have a little Kubota engine, but the CHP unit might not be made by Kubota.  I'll have to take a closer look at one the next time I see one.

Your setup, on propane, is a good setup though too.  LP has nothing to contaminate the oil, really.  It's kind of like my EcoGen on propane - they claim the engine lasts as long as a diesel because of the clean burning fuel.  And it actually starts in the winter time at 20 below zero, where a diesel needs pre-heat.
--
Chris

[ChrisOlson]

We got hold of a Honda EU3000iS inverter generator and tested it today.  The Honda is about the same as the Yamaha within a few tenths



I think I've seen enough to conclude that inverter generators are only slightly better than a conventional one at really light loads.  And they are worse, as far as fuel consumption, at anything above about 30% load.

And none of the gas units can beat a diesel.

The Honda, however, is the quietest one we tested, by far.  It's so quiet that if somebody is talking while standing by it you have to touch it to make sure it's actually running.
--
Chris

[bob g]

Chris

thanks for going to the trouble to do the testing, i for one appreciate numbers from other real world sources.

fwiw

a 6/1 listeroid driving an st5 can attain very close to 8kw/hrs per US gallon of fuel, some can do a bit better with serious tweaking.

a S195 changfa can exceed 9kw/hrs per US gallon with relative ease driving a ST7.5 genhead, and with some attention to detail one can get the setup to right at 10kw/hrs per US gallon @ full output @ sea level  @ 70 degree's F ambeint temp and with a close cooling system using a 195 tstat and an electric fan controlled with a temp switch so that the engine can maintain between 205 and 215 degree's F coolant temperature.

a S195 changfa so setup can compete very  favorably with the best of the commercial generators in its class (~8kva)

the same engine setup driving a hd alternator that is controlled to operate under different parameters coupled with a very efficient inverter can achieve very near the same 10kw/hrs per US gallon of diesel at a lower engine rpm than would otherwise be needed to operate at 60hz (1800rpm)

i have a link somewhere to some test results and a white paper that shows very detailed testing of small gensets in three classes, all diesel engine driven. ( 3-5kva, 6-10kva, and 11-14kva iirc)

will see if i can dig it up and post the link if there is interest.

test  results like those provide a benchmark for folks like us to aspire to or work towards.

bob g

[ChrisOlson]

will see if i can dig it up and post the link if there is interest.

Bob, I'd be interested in looking at that.  I think a diesel would show some significant advantages over a spark ignition engine with an inverter setup.  Simply because a diesel can run at incredibly lean air/fuel mixtures at lower speeds that won't even make a spark ignition engine sneeze.
--
Chris

[bob g]

here you go Chris

http://www.victronenergy.com/upload/documents/VE_Marine_generator_test_RVA_07-jan-2008.pdf

i think this is it, however i have to run and didn't have time to read it all over, but looks right.

bob g

[ChrisOlson]

Thanks for the link, Bob.

We got hold of a Champion Model 46539 and tested it under the same conditions as the others.  The Champion is built in China but it's a very impressive little generator.  It beat all the gas units, including the Honda inverter gen, for efficiency at all but the lightest load.

What's really cool is that the little Chinese engine (196cc) is more efficient by a couple tenths of a percent than the Yanmar diesel under heavier load.  But the diesel still beat it for kWh/gal of fuel simply because diesel fuel has more BTU's per gallon than gasoline does.  The little Champion is by far the quietest of the non inverter gens and only about half as loud as the Generac.  It has 3500 continuous running watt and 4000 surge watt capacity.

On the surge load test the Generac is still king.  The Champion is about as weak as the Honda for powering surge loads.  The tag on the engine in the Champion said it's made by WangDong Machinery (or something like that) in China.  I know Champion Power Equipment is based in California but evidently they outsource their manufacturing to China.



--
Chris

[SparWeb]

You know me as a number cruncher...

Here's a little value added to the thread:



The X-axis uses each generator's "rated load" as the baseline for the percent load it was under for each step.
We all know how the "rating" is up to the whim of the designers, engineers, marketers, lawyers, etc....
But regardless, it really bears out the superiority of the diesel.

PS was that Champion always running the volts on the high side when idling?  123VAC isn't a problem, but it makes me wonder...

[ChrisOlson]

Spar - thanks for the graph.  That's really cool!

The Champion has a smaller engine than the other gas non inverter generators.  But they all have electronic AVR's and the voltage is really not adjustable.  The Honda EM4000 has an electronic governor and it has the best regulation of frequency and voltage of the non inverter units.  The others have mechanical governors and if you tweak up the governor you get higher frequency, but the voltage doesn't change.  It appears that they just got the AVR cranked up an extra volt on the Champion.

I didn't include the frequency numbers in the data, but the Champion also runs the highest freq at no load - about 63 Hz.  The others are about 62 Hz at no load (or very light load) except for the Honda EM4000, which is dead on 60 Hz all the time.  The Honda EM4000 has, by far, the best voltage and freq regulation of all the non inverter gens.

The inverter gens are as rock solid as you could possibly have a generator for regulation of voltage and freq.

I'd like to take one of those Champion engines apart and see what's in it.  I know it has a cast iron sleeve because it says so on it.  But I think it's also a high compression engine (higher than the other gas units).  You can tell by pulling the starter rope on it very slow that it has serious compression numbers because it virtually locks up when the piston hits the compression stroke and if you tug the rope hard at that point it will lift the generator off the ground before it  spins the engine.  The Champion has electric start with a wireless remote thing that is kind of cool too.  But the starter spins it really fast.  I think the Champion would be a bear to start with the recoil starter in the winter if it was really cold out.

But despite that, the tag on it says min 85 octane fuel.  So it must not be too far over 9.5:1 compression ratio.

As far as the "rated load" you really have to look at the circuit breaker on the output to determine what real rated load is.  The Generac has twin 13 amp breakers and I have them paralleled (that's the only one of the bunch I own).  So it's real world output at max is 25 amps @ 120 volts, or 3,000 watts.  If you try to push it to 26 amps it will blow one or both breakers.

The Honda has a switch on it for full 120 or 240 output.  It has a 30 amp breaker for the 120/240 "full" output, which means it's really a 3500 watt generator, not a 4,000.

The Champion has a 25 amp breaker on the 120 output, and I'm not sure if it will carry the full 25 amps continuous as we didn't try that.  So it's really a 3,000 watt generator, even though they call it a 3500/4000.

The Yanmar diesel is also limited to 30 amp output at 120 volt, which is 3500 watts with a little reserve, and that's what Yanmar says for continuous power is 3500.

So the Yanmar and the Honda EM are realistically rated.  The Generac and the Champion are both a little "optimistic" as far as what they claim they're rated at vs what they'll really put out.
--
Chris