Where I live in North Carolina, if i put more power into the grid then I use the utility company keep it and I get nothing for it.
But still, I use more then 250 watts per hour all day long. If I put in 1000 watts I could run electric heat and be happy about it.

LEDs don't just change color without some kind of signal. In most cases each LED is driven, usually red, blue, and green, just like a TV has so they can create any color. You should open it up and see how it drives the thing, unless you are worried about the warranty of course. (post pics of the insides!)

The only other way is if it has a USB interface and then you could monitor it with a laptop and maybe make a script to do what you want. Drive a relay from the parallel port or something. But that would also take some power, probably about 25W 24/7 for a small laptop.

I have another idea, you could wire in a small 5V wall wart transformer (or whatever you have laying around) to the AC in the back of your fridge so it comes on when your fridge does.

Then you have a nice, low voltage signal that could pull in a relay or something to turn on the GTI.

You could go wireless if you could find something that would send out a wireless signal to a relay as long as it's powered up. Like maybe some sort of wireless alarm or doorbell. You would have to make sure it sends a signal all the time, or get in there and modify it so it does. Like on the doorbell, maybe you could just short out the door bell button.

Maybe with that you could have several senders that trigger the GTI for other loads.

With wireless there's always the chance of RF interference that might trigger the GTI when you don't want it to.

It's too bad you can't get a KAW to do this, they are only $15 and so it's not a problem to take them apart. There is a circuit someone built to send out the volts /amps from a KAW wirelessly. "Tweet-A-Watt".

They attach to the KAW at the points where it senses the V/A at a op-amp. It might be possible to make a circuit like they had but it simply sends a continuous wireless signal at some V/A amount you set. A lot of trouble that way though.

http://www.ladyada.net/make/tweetawatt/

I see that the Wattson lights up green when you are putting energy into the grid, so it may be possible to connect into that circuit and if it goes green, you open a relay or SSR and that would stop the GTI.

You would also want to put some sort of delay in there and keep the GTI off for a while so it doesn't go on/off over and over. Possibly a simple one transistor circuit and a capacitor, just to keep things simple.

If the LEDs to create the colors are all separate it should make things easier.

Since a SSR is simply a LED for a driver, you might be able to connect it directly in place of the red LED, and as long as it is in the red mode then the GTI would be on. You may still need a delay, so since you need a circuit for that you probably want to just go for the green LED mode.

It looks like you will be configured for a 12V system, and if so then the GTIs you have ordered will only drop the batteries to 10.5V, which is a good thing.

You might want to consider going 24V someday, you will get more performance out of your system that way, and it looks like the GTIs will handle it but it will pull a 24V bank to 10.5V which probably isn't a good idea.

However, since the GTIs are isolated on the AC side it may be possible to connect them to each 12V battery in a 24V configuration. I don't know for sure and you would have to be very careful in doing that and measure everything to make sure there's no problems and both GTIs are really isolated properly.

Interesting project, keep me updated!

Hi Electron,

Thanks a lot for your long reply
Yes my meter is digital and won't turn backwards I was told,
I leave in France btw, so anythink I push back into the grid would be lost
I ordered from eBay two 250 power inverter to test this for real
Like I wrote I just got a great power monitor called Wattson and this mesure in Real Time my consumption, and my production, and it provides the net amount. Whith this information, as soon as it goes negative, I could lower the inverter's output to avoid wasting power

Hi all,

I have been playing with solar panels, batteries, solar charge controllers for a year and I recently got a Wattson (Energy monitor very well done) and can now see my real time grid consumption. I have also been looking at grid tie inverters.

I have an idea / goal: I would like to be able to match my grid consumption using a grid tie inverter and my 12 V AGM batteries (2 x Yuasa 65 AH)
I know how a GTI works, but do you think it would be possible to control its AC output so that I use just the required amount of battery energy to match my consumption;
For example: my fridge starts for 5 minutes, using 100 W, and I would like the GTI  to start and give an output of 100 W during these 5 minutes and then stop or reduce its output to match the remaining house loads
I thought of a "dimer" plugged on the GTI output, before plugging the socket into the wall

Any ideas ?
Thanks a lot in advance

Chris