Generator/Inverter generator options

photonboy · June 2022

Looking for help selecting/sizing a generator for my off-grid cabin. I have an Outback VFXR3524A which suggests 2230VA of power to charge. Is there a reason I need to get an inverter/generator or can I go with a just a generator (considerable cost savings); I was going to go with a Honda EM 6500. I planned on using the generator for battery charging through the inverter, 240V well pump, and power tools. My computers are laptops and I have an AC fridge. Any guidance/advice appreciated.

Chris

mike95490 · June 2022

Any well tuned conventional generator should be stable enough to work for you. An inverter-generator is an unneeded expense

photonboy · June 2022

Thanks Mike. That is what I was thinking. Appreciate the help

Chris

BB. · June 2022

When picking a genset... Sizing the genset to the load is also important....

For gasoline/propane type genset, the "standard" alternator type, is most efficient when running from 50% to 100% of rated output. When running a standard type genset below 50% of rated output, the fuel flow only drops a little from 50% loading to 0% loading (motor must keep generator spinning at 3,600 or 1,800 RPM for constant 60 Hz output).

Inverter type generators--They are fairly fuel efficient down to 25% of rated load... So if you spend lots of time with light loads, an inverter-generator can save you lots of money on fuel bill.

In your case, needing a 240 VAC genset--You are limited in how many "smaller capacity standard or inverter gensets" that have 120/240 VAC output...

So, what is the AH and voltage rating of your battery bank... Typically 10% to 20% charging current suggested for your battery bank. And I suggest that your load your genset for 50% to 80% of rated output (residential gensets should be derated to 80% for continuous loads like charging a battery bank).

Running the genset (when needed during bad weather) in the early mornings and letting solar take over the late morning/afternoon is fuel efficient. Also, charging the battery bank from 50% to 80% with genset (even if there is "no sun") is also fuel efficient and good for battery health (you only need to charge to >90% SoC once a week to even once a month--If you are daily cycling the battery bank). One need to charge >90% when putting system away for winter (and/or leave on solar charging during winter)....

The other option is to have two gensets--One large genset for heavy power needs (battery bank charging, running shop tools, etc.). And a smaller 2k-3kWatt or so genset for emergency backup / portable 120 VAC power. Years ago, Honda was (pretty much?) the only company that offered true sine wave inverter-generators. Today, PSW/TSW inverter generators seem to be the standard (MSW is "hard" on some AC electronics/induction motors/refrigerators/etc.).

Also for electric start generators--You might want to look at a small solar panel + charge controller to float charge the battery when not in use.

https://powerequipment.honda.com/generators/models/em6500

AC Output 120/240V 6500W max. (54.2/27.1A) / 5500W rated (45.8/22.9A)

iAVR Output 7000W (58.3/29.2A) for 10 sec.

Fuel Tank Capacity 6.2 Gallons

Run Time per Tankful 6.4 hrs.@ rated load, 9.8 hrs. @ 1/2 load

full power Watt hours per gallon = 5,500 Watts * 6.4 hours * 1/6.2 gallons = 5,677 WH per gallon
1/2 power WHpg = 5,500 Watts * 1/2 load * 9.8 hours * 1/6.2 gallons = 4,347 WH per gallon
Fuel flow full power = 6.2 gallons / 6.4 hours = 0.97 GPH
Fuel flow 1/2 to 0 power = 6.2 gallons / 9.8 hours = 0.63 GPH

https://powerequipment.honda.com/generators/models/eu2200i-companion

AC Output120V 2200W max. (18.3A) , 1800W rated (15A)

Fuel Tank Capacity 0.95 gal.

Run Time per Tankful 3.2hr @ rated load 8.1 hrs @ 1/4 load

full power WH per gallon = 1,800 Watts * 3.2 hours * 1/0.95 gallons = 6,063 WH per gallon (full power)
1/4 power WH per gallon = 1,800 Watts * 1/4 loading * 8.1 hours * 1/0.95 gallons = 3,837 WH per gallon (1/4 power)
Fuel Flow full power = 0.95 gallons / 3.2 hours = 0.30 GPH (full power)
Fuel Flow 1/4 power = 0.95 gallons / 8.1 hours = 0.12 GPH (1/4 power)

To run "light loads", the 6,500 Watt genset will use (0.63 gph/0.12 gph = ) 5.25 times more fuel -- So it is very important (fuel cost wise) to size your genset to your needed/expected loads & usage.

Charging a good size battery bank for hours at a time at 50% to 80% loading, a "standard" genset will be very nice and cost effective.

For building your cabin/home (as an example) where you are running circular saw and charging power tool batteries for relatively short periods of time, but running the genset 8-10 hours of day (at low power, or no power) a standard genset will just suck down the fuel.

I used Honda here as they have pretty good specifications (they tell you 100%/50%/25% fuel usage). But there are a bunch of other brands out there in standard and inverter genset types--And it makes it hard to ignore the cheaper brands out there...

Plus those of us in California--The present SMOG/Emmisions laws seem to have kicked Honda out of the market for now.

-Bill

Generator/Inverter generator options

Comments

Categories