whole house monitoring

Re: whole house monitoring

Brock,

How will that unit work for Grid Tied Inverters... Nothing on their web site says anything about the ability to log power direction, but I would guess if it is a simple current clamp that the TED cannot tell the difference between incoming and outgoing power... I.e., when I use 10 amps, and when I generate 10 amps, the TED will read the same thing (no minus sign, etc.) and just add up generated power as power usage.

-Bill

Re: whole house monitoring

Thank you Brock,

Interesting it went to zero... If it can do that (read zero when power is being pushed back to the utility), then it should be able to measure reverse power too. Perhaps it is worth an email to them to ask and inform them of this new thing called "grid tied" solar (perhaps, they are trying to prevent very low power readings from ever reading negative and confusing the owner).

In California, there is only one utility meter required for Net Power billing/usage... And in my case, the grid tied inverter is just another two pole (240vac) breaker in my main panel--so I can read the inverter power, but everything else is simply added together in the main panel's bus bars.

From what I understand in a few emails to Darell, he had two meters--one was the standard E7 Time of Use meter for residential power (now restricted to current customers only as the rate is really too good for the solar PV user and not so good for the utility), and he had a second meter just for charging his electric vehicles (with a very deep discount for middle of the night usage).

But (I am sort of guessing a bit here), he gave up the second meter because of the way PG&E calculates base line rates (first 300 kWhr/month is one rate, next 100-120% another, 120% to 200% a third, 200% over is another rate, 300% is even a higher rate)...

The crazy part about the rate is that, one would think that baseline would be credited (or at least ignored) for the periods you are generating power... However, what really happens is that the power you generate also pushes up your baseline total.

For example, two meters (one residential TOU, one special Electric Vehicle TOU), two time of use periods. During peak-residential TOU (noon-6pm/off peak), I am net positive generation by -183/-115 = -298 kWhrs (peak = $0.29 / off-peak = $0.09/kWhr). (real numbers from last July from my system).

Now, I take the Electric Vehicle rate E-9... One would think that Darell could charge at $0.05/kWhr--but no... In my case, I would be at ~300 kWhrs of total usage (no matter that I GENERATED THIS BASELINE USAGE POWER, NOT CONSUMED THIS POWER). Take the E-9 EV charging meter, and at 131% of baseline (300 kWhrs in my case), if I use anymore power than 90kWhrs that month to charge my vehicle, I would be paying $0.15/kWhr, and if more than 300kWhrs of EV meter use, I would be paying $0.29/kWhr of energy use...

So, basically, in my case (using my best summer numbers), I generated an extra 300kWhrs of power, and if I used the E-9 EV meter, I would have to pay upwards of $0.15 per kWhr for power I generated (at $0.29 and $0.09/kWhr).

If, however, I charged from my E-7 OPk meter, I would only pay $0.09/kWhr and I would be reducing the -115 kWhr off-peak baseline, and I could go another ~115 kWhrs of usage, and still be at baseline paying $0.09/kWhr. And I could play more games to figure out if I would be better paying the next higher tier in E-7 OP of $0.19/kWhr or using more of my (generated PK baseline) that the utility "paid" me $0.29/kWhr instead (which reduces my -183kWhrs baseline amount, and gives me more $0.09/kWhr baseline to consume)...

And, in reality, from what I understand, it even gets a bit more complicated than that during the billing... They allocate the baseline rates, based on percentage of usage, across the all of the meters and TOU's periods--So (for example) 1/3 for E-7 TOUPk, 1/6 for E-7 TOUOPk, 1/6 for E-9 TOUPk, and other 1/6 for TOUOPk. And, you you will end up paying higher prices for off-peak power (even though you were generating, not consuming, power from noon-6pm).

It hurts my head to figure out the mess of the interaction between the meters, baseline, rates, etc... And, from what I have read from Darell, if there is a question or confusion in the way the rates are applied, the method that is most favorable for the utility is chosen (like, who would of thought that baseline would be used up by both consumption and generation).

In the end, Darell yanked his E-9 EV TOU meter a while ago (for the above reasons--I think).

At this point, I don't think I could even write a spreadsheet or computer program that would allow me to enter "what-if" numbers at the beginning of the month so that I could manage my power among all of the TOU + two rate schedules + baseline to optimize my usage.

And, you have to be very aware of what you are doing here--The lowest price is around $0.05/kWhr and the highest is $0.53... Do something wrong, and you could be paying 10x the price if your baseline/timer/branch circuits are used incorrectly. And, you really don't know what you did wrong until the next bill arrives in the mail.

-Bill

Re: whole house monitoring

When I first connected with the grid tie (a little over 1 year ago)--there was a week or so overlap between the approval and changing out my meter... So, I had 100-200 kWhrs of generation on the old meter.

Apparently, the meter reader read the meter correctly, but there was a software hack that attempts to correct miss-reads. So, I would guess, if there is a "negative power usage recorded" that they add 1, or 10, or 100, or 1,000, etc. until the readings are positive again (assuming that was the digit that was miss-read). My first bill for 1-2 weeks of usage was for 800-900 kWhrs (or ~$400) instead of a credit of ~100-200 kWhrs... They refused to credit the bill, but did knock it down to the minimum payment.

Needless to say, my wife was none too happy. Darell said that almost everyone had a 1st month bill horror story with solar PV and PG&E.

Also, I did drop the folks at "TED" a question about their whole house monitor and grid tied systems (with a link to this thread). I will let you know what they say.

-Bill

Re: whole house monitoring

And they are almost two years behind the date they told me a net metered version of this unit would be available.

-Bill

Re: whole house monitoring

Just a couple warnings that apply to most whole house monitors:

1. Some clip onto the meter and watch the disk spin or on the optical port (one blink per revolution). At least one utility took a bi-directional link off of the meter and threatened service (guy programmed up his own two way interface that could read the "public" data registers).
2. None of the systems that I have seen (I have certainly not seen all, or have read all of the manuals), at this time, will work with net metering... At best, they appear to add up energy consumed and energy generated into the "energy consumed" bin. T.E.D. has been promising a Net Meter unit for years.

Perhaps the "T.E.D." like system that WindSun said (in another thread) that will be out in the next few weeks will address some of these issues. Might be worth waiting to see what this new product looks like.

The other thing to watch for (perhaps, "look out" for--assume that this going to increase our overall rates)--Smart Meters. Sounds like, for California at least, that these will be rolling out over the next couple years--may include a web based interface (through the utility).

-Bill