Offset your power bill with your solar parked in the driveway? Probably not.

[fourstringfletch]

Right now I'm looking at the window at my beautiful 85w panel on my truck basking in the sun. I know the truck batteries are topped off as they are most of the week, and I wonder what it might involve to feed this unused potential though my meter at home.

Is this possible? I'm thinking no, but hoping you guys know something I don't. Here are my thoughts:

- Can I find a controller/inverter to add to my house that's designed to sync with the grid and then plug my panel in to that? As I understand it, these are pretty specific to the number of cells in the system and not likely to work with something as small as 85w.

- Can I run an inverter of some sort from the truck to convert 12v DC to grid tied AC? I'd somehow need to switch the inverter on only once the controller reaches float state.

The easy answer is to just run an extension cord from my 700w inverter into the house and power stuff from that. I'd rather not cycle my batteries though and I'd like this to be as automatic as possible - somehow feeding the house only after the truck is topped off and being able to come and go in the truck without a wiring project every time.

One final doubt is that the power company would buy back such a small amount of power. I average about 120 KWH / month, and I might produce 10% of that if I'm lucky.
This final point just came to me, and rather than scrapping what I just wrote, I'll throw this out there to save anyone else the time who has the same idea.

My conclusion: don't bother.

 

[pugslyyy]

I agree with your conclusion, you are just generating such a small amount of power that it would never be cost effective. Much more useful has a source of backup power (or backup living space) in the event of power failure.

 

[madmax718]

The short answer is yes.

The not so easy answer is.. maybe. It depends on your local laws, and your power company.

http://www.amazon.com/300W-Micro-Po...=1369436317&sr=8-5&keywords=grid+tie+inverter

Their called plug in grid tie inverters. I've never tried them, but the theory behind them is sound; convert 12v power into 120v (much like an inverter) but with electronics to detect grid voltage.

The basic way it works: You need 500 watts of power for your computer. You make 100 watts on solar. The grid tie would feed 100 watts of power, and then take only 400 watts from the grid.

The finiky part is to not A. Backfeed into the grid (use more than you make) and B. Make sure its legal in your area.

Your mileage may vary.

 

[dwh]

Just about anywhere in the states - if you feed power to the grid, your gear has to be UL approved, and the installation has to be permitted, inspected and up to code. Besides being approved in advance by the utility company. Which means those plug-in grid-tie inverters are probably always illegal.

How much power would you feed in? How much would you save? How long would it take to amortize the cost of the inverter and actually save any money?

If there's a fire, even if it wasn't caused by the inverter, your insurance company will probably jump all over that as illegal electrical and try pushing it as a reason to not pay off.

I wouldn't even consider using one of those plug-in grid-tie inverters. On a house anyway...I could think of a few backyard projects where it might be fun to play with.


If your solar charge controller has a low-voltage disconnect, you might try using that for something like charging a battery to run your Malibu yard lights or some such. But overall, I agree...

Don't bother.

 

[madmax718]

Grid tie power is actually quite safe- You just use less from the line. The problem comes when you generate more than your max capacity is to use it. Then your backfeeding into the rest of the grid.

This creates all sorts of potential "safety" issues- if they take the line down for maintenance and your still feeding power into it.

For such a small amount of power, it works fine. I'd be more concerned about the grid tie inverter frying or something than anything else.

 

[dwh]

This creates all sorts of potential "safety" issues- if they take the line down for maintenance and your still feeding power into it.

That's kind of a common misconception.

Grid-tie inverters require power coming from the grid so they have something to sync to. If the grid power goes down, then the grid-tie inverter shuts down as well. Highly unlikely to feed power into the grid in that situation unless the inverter is broken somehow.

 

[madmax718]

I say potential because the one I see for sale must have AC sync before it begins transmitting power. but I have seen ones that do not need it. :Wow1: The stuff you find overseas sometimes.

 

[Wicked 2007]

The short answer is yes.

The not so easy answer is.. maybe. It depends on your local laws, and your power company.

http://www.amazon.com/300W-Micro-Po...=1369436317&sr=8-5&keywords=grid+tie+inverter

Their called plug in grid tie inverters. I've never tried them, but the theory behind them is sound; convert 12v power into 120v (much like an inverter) but with electronics to detect grid voltage.

The basic way it works: You need 500 watts of power for your computer. You make 100 watts on solar. The grid tie would feed 100 watts of power, and then take only 400 watts from the grid.

The finiky part is to not A. Backfeed into the grid (use more than you make) and B. Make sure its legal in your area.

Your mileage may vary.

I could be wrong - but I believe the new "smart meters" (if you have one at your home) will detect these units.

 

[Gooseberry]

Your 12v panel will not work with the solar inverter. The inverter needs to see over 240 volts dc min to run and that's why those panels are set to higher higher dc volts and its how you series parallel them to get the current and voltage levels you need for the inverter to operate at it most efficient.


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[Wicked 2007]

Your 12v panel will not work with the solar inverter. The inverter needs to see over 240 volts dc min to run and that's why those panels are set to higher higher dc volts and its how you series parallel them to get the current and voltage levels you need for the inverter to operate at it most efficient.


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these particular small units will run off a 12v panel - that what they are designed for - my concern is smart meters will detect them and if not permitted correctly could be illegal

SPECS:
Normal AC Output Power:250W; Maximum AC Output Power:300W
AC Output Voltage Range: 90V ~ 130V; DC Input Voltage Range: 10.8V ~ 30V; Total Harmonic Distortion(THD):<5%; Power Factor: 0.99
AC Output Frequency Range: 46Hz ~ 65Hz. Peak Inverter Efficiency: 92%; Output Current Waveformure Sine-wave; Standby Power consumption:<0.5W

 

[dwh]

I doubt a smart meter would detect it unless there was a backfeed to the grid. If not permitted correctly, it will almost certainly be illegal.

 

[Gooseberry]

You need to make sure they have source sensing to match the line voltage from the utility and shut off when the power is lost so you do not back feed on the line and hurt a worker.

If you use a normal inverter it will let the smoke out.


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[Wicked 2007]

I doubt a smart meter would detect it unless there was a backfeed to the grid. If not permitted correctly, it will almost certainly be illegal.

Spoke with my buddy who work on smart meters at PGE in CA. He confirmed a smart meter will detect the use if these. Now what happens when it is detected - that's unknown.

 

[Crom]

There is an easier way, but not really what you want to hear. Use a 12v light at night instead of your AC porch or patio light. That's what I do in my back yard. When I go on an expedition ( camping ) battery and panels get loaded onto truck. My setup is portable and severable from the truck, it is one on the requirements when I designed it.

 

[madmax718]

That certainly works but invovles the use of a lesser efficient battery bank instead of letting the grid handle it. There's also more wear and tear on your battery bank system.