Grid-Tie with "Smart Meter".

[Andy Rhody]

We got our 2000 watt windmill all legally grid-tied with a REAP agreement and started making power around the 2nd week of October. Although we've made 175 KWh's of power so far, we haven't seen anything about it on our billing statements so the wife and I stopped at our utility's office (REA) this week and talked to the secretary.

A little hard to follow but here goes:

The smart meter unlike the old type meters will not run backwards. If we are using 1000 watts and the windmill is making 400 watts, then only 600 watts runs through the meter to the panel box so we are only charged for 600 watts. Now if we're using 1000 watts and the windmill is making 1600 watts, then the extra 600 watts will be added as a credit. In other words we only accumulate credits when we are pumping power back into the grid.

So how does the credit thing work? Credits are awarded in increments of "10". You need to produce 10KWh's of credits to be credited to your bill and then you need to wait until you get 10 more berore you can be credited again. As of our last bill, we had less than 10 credits so nothing was credited to our bill but she informed us that we are now over 10KWh's or credits so our next bill should reflect that.

Below the meter on the left is the windmill meter. She said that they don't even read it but they can. I asked her how the meters are read and she said that she didn't know. In the middle is the lockable shut-off switch and on the right is the regular meter which blinks between the regular reading and the "credit" reading.

http://i41.photobucket.com/albums/e295/andy47bottles/Science/001-4.jpg

Here's a vid of it blinking.

Blinking Smart Meter. - YouTube

[Rob Beckers]

Andy, how is that second (windmill) meter connected? Do I read correctly that current flows from the windmill through that new meter, to your distribution panel, and then back out through your original meter (so in effect the two meters are in series)? Or is the new meter connected in parallel with the old one?

If it's the first one (series) then the story of your electrical company is correct. Whatever your windmill produces will be used locally first, offsetting your local electrical loads (lights, TV, A/C, etc.). The energy from the windmill never goes through your electrical meter (the original meter), so it doesn't register your production and the power company doesn't know how much you're producing (they would have to read that new meter to find out). Only if you produce more than you're using will the meter "spin backwards", if it was an old one, the new ones as you noted just register the direction. It would be rare for a relatively small windmill to produce enough to offset your entire household loads at any moment, so your old meter will rarely show any power flowing out to the grid. These meters blink between use and production (big number is how much you've used, small number is what you produced) so you can find out how often net-production happened.

Most places won't even bother to install a second electrical meter for net-metering; They simply look once a year at how much your (single) meter says you used, and how much you produced, subtract the two, and you pay for your net-use.

By the way, these new meters are read out wirelessly. Since they are reading your old meter I'm pretty sure they are also reading your new one (if it's registered in their system it'll be read), so they have the production info somewhere in their system. Not sure why they want to know production, it's not needed for billing nor refunding, your original meter is all that takes. Maybe they want statistics on what people produce locally?

-RoB-

[Andy Rhody]

Yes Rob, I guess that you would say that the meters are in series and I agree with your explination of everything else.