Using car as generator for house power

There are more than one way to save money with a Prius.

Good enough for a trade-study that compares requirements versus specifications:

	Column 1	Column 2
0	[th]Tri-Fuel Generator[th]Prius Inverter[th]Specification
1	[tr][td]$1	199+shipping[td]$100-300[td]cost
2	[tr][td]10kW[td]1kW (12V) / 2kW (200V)[td]available peak power
3	[tr][td]extra fuel source	often manual[td]same as Prius[td]fuel handling
4	[tr][td]small engine shop[td]Toyota service[td]maintenance
5	[tr][td]heavy to lift	trailered or ramps[td]anywhere a Prius can go[td]transportable
6	[tr][td]unavailable[td]available[td]usable when driving Prius
7	[tr][td]hazardous[td]2-10% less CO[td]generator carbon monoxide kills every year
8	[tr][td]nosy[td]nearly silent	intermittent engine[td]noise
9	[tr][td]during next outage[td]daily[td]reliability	test frequency

Source: specifications provided by anti-Prius power skeptic

The only specification where the generator exceeds the Prius is in peak power. In every other metric, the generator takes: more fuel labor; small engine support; less transportable; no AC power during Prius trips; makes a poisonous gas; loud; and tested at the beginning of the next power outage.

So there are trade-offs so let's go to a primary requirement, the power needed, where the dedicated, 10kW generator exceeds and see the effect:

	Column 1
0	[th]Watts[th]Load[th]Prius 12V[th]Prius 200V[th]10kW Gen
1	[tr][td]10[td]Clock radio [td]X[td]X[td]X
2	[tr][td]20[td]VCR/DVD [td]X[td]X[td]X
3	[tr][td]20[td]100W CFL[td]X[td]X[td]X
4	[tr][td]25[td]VCR/DVD [td]X[td]X[td]X
5	[tr][td]50[td]Aquarium [td]X[td]X[td]X
6	[tr][td]50[td]Laptop [td]X[td]X[td]X
7	[tr][td]55[td]Fans Window [td]X[td]X[td]X
8	[tr][td]60[td]Electric blanket [td]X[td]X[td]X
9	[tr][td]65[td]Fans Ceiling [td]X[td]X[td]X
10	[tr][td]65[td]TV 19" [td]X[td]X[td]X
11	[tr][td]70[td]Radio[td]X[td]X[td]X
12	[tr][td]100[td]Electric blanket [td]X[td]X[td]X
13	[tr][td]110[td]TV 19" [td]X[td]X[td]X
14	[tr][td]113[td]TV 27" [td]X[td]X[td]X
15	[tr][td]120[td]PC CPU - awake[td]X[td]X[td]X
16	[tr][td]120[td]TV Flat screen [td]X[td]X[td]X
17	[tr][td]120[td]Water bed [td]X[td]X[td]X
18	[tr][td]133[td]TV 36" [td]X[td]X[td]X
19	[tr][td]150[td]PC Monitor - awake[td]X[td]X[td]X
20	[tr][td]170[td]TV 53" - 61" Projection [td]X[td]X[td]X
21	[tr][td]175[td]Fans Ceiling [td]X[td]X[td]X
22	[tr][td]240[td]Fans Whole house [td]X[td]X[td]X
23	[tr][td]250[td]Water pump [td]X[td]X[td]X
24	[tr][td]250[td]Fans Window [td]X[td]X[td]X
25	[tr][td]350[td]Clothes washer [td]X[td]X[td]X
26	[tr][td]380[td]Water bed [td]X[td]X[td]X
27	[tr][td]400[td]Radio[td]X[td]X[td]X
28	[tr][td]500[td]Clothes washer [td]X[td]X[td]X
29	[tr][td]725[td]Refrigerator [td]X[td]X[td]X
30	[tr][td]750[td]Fans Furnace [td]X[td]X[td]X
31	[tr][td]750[td]Heater[td]X[td]X[td]X
32	[tr][td]750[td]Microwave oven [td]X[td]X[td]X
33	[tr][td]750[td]Fans Whole house [td]X[td]X[td]X
34	[tr][td]785[td]Dehumidifier [td]X[td]X[td]X
35	[tr][td]785[td]Window AC[td]X[td]X[td]X
36	[tr][td]800[td]Toaster [td]X[td]X[td]X
37	[tr][td]900[td]Coffee maker [td]X[td]X[td]X
38	[tr][td]1000[td]Clothes iron [td][td]X[td]X
39	[tr][td]1000[td]Vacuum cleaner [td][td]X[td]X
40	[tr][td]1100[td]Microwave oven [td][td]X[td]X
41	[tr][td]1100[td]Water pump [td][td]X[td]X
42	[tr][td]1200[td]Dishwasher [td][td]X[td]X
43	[tr][td]1200[td]Hair dryer [td][td]X[td]X
44	[tr][td]1200[td]Coffee maker [td][td]X[td]X
45	[tr][td]1210[td]Aquarium [td][td]X[td]X
46	[tr][td]1225[td]Toaster oven [td][td]X[td]X
47	[tr][td]1400[td]Toaster [td][td]X[td]X
48	[tr][td]1440[td]Vacuum cleaner [td][td]X[td]X
49	[tr][td]1500[td]Heater[td][td]X[td]X
50	[tr][td]1800[td]Clothes dryer [td][td]X[td]X
51	[tr][td]1800[td]Clothes iron [td][td]X[td]X
52	[tr][td]1875[td]Hair dryer [td][td]X[td]X
53	[tr][td]2400[td]Dishwasher [td][td][td]X
54	[tr][td]4500[td]Water heater[td][td][td]X
55	[tr][td]5000[td]Clothes dryer [td][td][td]X
56	[tr][td]5500[td]Water heater[td][td][td]X

Source: Estimating Appliance and Home Electronic Energy Use | Department of Energy

With the Prius 12V solution, more load management as everything can not be run at the same time. The Prius 200V solution provides more capabilities. It is in hot water heating that the 10kW generator exceeds. If there were just some way a Prius could provide hot-water . . .



Bob Wilson

 

Among the idiotic things we found done by the previous owner here (he remodeled and added-on to the abandoned farmhouse to bring it to its present size) was that the gas furnace AND the wood stove were vented into the same flue! That's a huge no-no!

We chose to disconnect the gas furnace that winter and just ran on the wood stove, partly because we wanted to see how it would be. This was in January or something, the middle of the Nebraska winter. The gas technician asked us several times if we were SURE that we wanted our gas disconnected.

Since this was before we even knew what closed-cell foam insulation was, running on just the wood stove was pretty uncomfortable. Multiple layers of clothes and cut-off gloves in the house were the standard, but we survived.

Now with the upgraded insulation and a single 400W radiant panel in a far room it's comfortable. We *do* have a few more areas to re-insulate though, but tearing all the drywall (and taking all the cabinets out of the kitchen!) were a bridge too far. We still need to re-drywall from the last time, but I wanted to do some built-in storage and re-wiring before we cover up all the stud locations again.

 

Actually with my system I can run an electric water heater and/or well pump. I just chose not to move those loads over to my UPS/Prius subpanel. I would also have to do some load management, so I avoid that by leaving them on the big genset. But I only have to run it 1-2 hours a day now (during an outage).

 

At least the kitchen cabinets act as an insulative layer by trapping air while closed.

 

Yes, a little, but not very well, and they certainly do not have the air and moisture barrier properties that the closed-cell foam do!

Stopping air infiltration is a biggy. Fiberglass batting is tested assuming no air infiltration, yet this is not realistic in homes, so their actual performance is worse than their rating.

 

I installed a tankless water heater fueled by our natural gas utility line. That was six years ago. Does fine for two "endless" simultaneous showers. The electric load is tiny. In a small 1939 house, the space saved by eliminating the water heater barrel (along with other changes) allowed code-compliant installation of the 2d bathroom.

My AIMS 2kWatt inverter + PiP installation might - or might not - power the compressor for the ground-source heat pump. I'm waiting for better weather for a full install. If this 2KWatt base power can handle the GSHP's compressor surge without tripping the breaker, then we'll have both heat and A/C . if the GSHP will keep tripping the breaker even with load mgmt, then we'll have heat (backup gas furnace) but no A/C.

I agree the closed-cell insulation has to be lived with to be believed. We blew the 2-lb stuff onto the underside of the cement roof, and followed with the 1/2 lb stuff onto the underside, and in all the walls and also interior walls. Talk about a quiet house! in a major 1930's-era suburb too! We NEVER hear the street unless there's an ambulance with sirens right in front. And the Federal tax credit helped as well.

 

Love the concept picture! Mebbe it'll cool the exhaust enough to precipitate the carbon out so it'll also slow global warming...

 

By micro-inverters, I assume you are talking about the Enphase system? That's just to connect your PV to grid, doesn't do anything when the grid goes down.

Comparing a 10kw gen set to a 3kw prius inverter is unfair. Even still, that fuel consumption is wrong. This unit uses only 1 gallon an hour at 50% load:

Generac XG10000-Watt Portable Generator-5802 at The Home Depot

The web site UtterPower.com | Alternative Energy Solutions describes how to build your own 10kw gen set out of an old, heavy, cheap, reliable lister type 2 cylinder diesel engine that apparently uses less than half a gallon an hour, and can burn vegie oil.

 

You can not go to dinner because no restaurants are open because they have no power. If they are open, the house doesn't need power while you are out. Also the cost of the prius doesn't matter. The question is whether to spend $80 on an inverter, or much more on a generator that burns more gas.

 

Enphase and other grid-tie inverters can be tricked into operation when the grid is down. Sunny Boy has a system where they intentionally do this, others have been done ad-hoc using an XW as the frequency driver. Usually the system frequency is varied slightly to notify the grid-tie inverter of how much power to output.

Comparing a 10 kw with a 3+ kw Prius is entirely fair. Remember that the Prius can output much more than 3 kw. It will surge much higher than 10 kw, and it can maintain 6 kw for an hour. The ONLY thing my Prius can't run in my house is the 2-ton A/C units, which I haven't needed in the 8 1/2 years I've had my 12 kw Generac. My Prius system can run my 1 hp well pump, my 3 kw water heater, and everything else. Running "everything else" doesn't require load management, the well and water heater do.

The XG10000 is a gasoline unit which is why it only uses 1 gallon per hour. Gasoline has a higher energy density than LPG or NG. The 10 kw and 12 kw Generacs mentioned before are LPG and do use 1.25 and 1.5 gallons/hour respectively.

Sure, Listers are great. But diesel gensets are horrible for home power backup. You must keep a diesel engine above 40% load most of the time or you will encounter "coking". Unburned fuel builds up and kills the engine. Diesel is great for commercial loads where the building load is usually constant. Home loads can vary from 200 watts for 16 hours a day to 1500-3000 watts for a few hours, to brief spikes of 10 kw. If you size a diesel genset to handle the surge loads in a home it will run well below 40% load 98% of the time. Then the engine dies.

 

You definitely don't live where I do. 10 minutes north of me and you are on a completely different grid in a different state. 10 minutes south and they are on a different feeder than mine, in a highly dense area which always gets power back quickly because of the schools and fire houses. Besides, I didn't say I was going out for dinner, during a disaster I'd much rather stay home and fire up my own grill.

You are correct, the cost of the Prius is a sunk cost if you already own one. The question is whether to spend $80 for the cheapest piece of crap modified sine wave inverter you can find, $300 for a decent sine-wave model that will give you a few hundred watts at 120 volts single phase, or $500 for my complete setup (250 for the UPS, 250 for the step-down transformer) which gives me thousands of watts and 240/120 split phase output.

 

Good deal. I looked into the tankless systems a few years ago, but we have a high mineral content in our well water and I'm worried about the tubes clogging up. When my current water heater goes up I'll either change to a heat-pump water heater or a gas-powered water heater. I prefer to stay all-electric for the eventual day that we go solar.

 

The XW will change the line frequency when the batteries are full to cause the inverters protection to kick in and shut down to prevent over charging the batteries. It does not regulate power output.

Last I checked, LPG was measured in pounds, not gallons. Let's stick to comparing apples to apples.

The people on that site don't seem to have that problem. Also it seems to me that the time you get unburnt fuel, evidenced by black smoke, is under very high load, not low.

 

My 10KW unit will run 8 hours on 8.3 gallons of gas, 6 hours on a 20lb propane tank, or indefinitely on a natural gas feed. It is connected to natural gas.

Powerland Tri-Fuel Gasoline Propane Natural Gas Generator 10000 Watt 16 HP

It is 220V and powers the entire house including my 3.5 ton AC compressor.

 

The solar forum in my signature, newbies come by asking "how do I get power from my grid-tie system during a blackout" about twice a week. I've seen the discussions on how the Sunny Island and XW regulates the grid-tie inverters enough times to know of what I speak. The controlling inverter regulates the output of the grid-tie inverter by varying the frequency, which modifies the output to match the load. It isn't just an on/off thing, sorry. Just one thread on the Sunny Island (note the author is in Spain so he refers to the frequency limits between 51 and 52 Hz) SMA Sunny Island AC coupling
And a mention on this page about half-way down about the XW modifying its frequency In an AC-coupled system, a grid-tied inverter can work with certain battery based inverters to supply electricity for critical loads when the grid is down. | CivicSolar

Well, my bulk propane provider must be billing me improperly because my delivery receipts and bills are both in gallons. Even the US Energy Information Administration puts out its weekly propane pricing reports by the gallon. Heating Oil and Propane Update - Energy Information Administration Sounds like apples to apples to me!

Same forum as paragraph #1, lots and lots of talk about coking.

 

8.3 gallons of gasoline = 946,200 BTU
4 gallons of LPG (20 lb tank filled to 80%) = 382,255 BTU

Since you won't get to the bottom of a LPG tank - not under load - your run time numbers match up just about right. LPG needs enough liquid to boil off enough vapor to support the load, which is why under load you'll still have some fuel in the tank when the genset dies. Under a light load you'll get to use more of the fuel.

 

We bought a Rinnai tankless (natural gas) about eight-years ago and never looked back.

I don't think I'd ever consider electric, even with my plans to go solar.

Knowing what I do about solar from my photovoltaics design class and about heat transfer from my heat transfer class, heating is an energy hog.

Best to transfer what loads make sense to gas or geothermal heat pump supplemented with gas and minimize the size of the battery bank and solar arrays that you will need to truly get independent.

Regarding the mineral content, is there a reason that you don't install a water softener to save the pipes?

The modern ones don't put a whole lot of salt into the system. And for pipes that you don't want softened (external hose bibs for example) you can plumb those separate from the softened water.

 

I will never get to the bottom of either. It runs on Natural Gas connected to the utilitiy compay. If by a freak of nataure Natural gas fails those are just a backup.

There is a far better chance of not being able to get gasoline or propane during a disaster like Katrina then houses with Natural Gas.

 

Actually keeping a large LPG tank on-hand is the more sure option. In major disasters NG usually fails within a few hours because the electric supply died so booster pumps are also dead, or the pipes broke. Look at at the 1989 California earthquake - lots of video of fires all over the place from broken pipes and that was just the breaks that were ignited. The area 10 minutes south of me lost water service and NG service within 12 hours after one of the hurricanes last year when the area's electric feeder was severed.

Close behind that is gasoline - it isn't hard to keep 20 gallons on-hand, which assuming a half-full tank on the Prius would last me over a week for an unexpected disaster IF I ran everything 24/7. During a major disaster I would conserve by running fewer loads and only running for 6-8 hours a day. Then those 20 gallons would last me a month.

When I bought my Generac and I did my research on which fuel supply to use, it was clear to me then - and still - that relying on NG during a disaster is a disaster.

 

Let me get this straight.

2013 – 1989 = 24 years ago is the best example of an issue or as you put it “relying on NG during a disaster is a disaster”. I kind of get the feeling you just like to argue and your ok with with crazy facts like that to make your point.

I think we should both agree to disagree. Some people want a 3KW solution and they are willing to use their car for this. Some people are ok paying a 3x in fuel a day ($80 total) to power the entire house. Both are good solutions. Using the Prius as a power source is not the solution for me and my family.