PV details for my own reference

I have three electric meters separated by about 1/3 mile.  The electric provider, BlueBonnet Electric Coop, treats them as essentially three different customers.  That is, PV (photovoltaic) over production on one meter can not be transferred to an under producing meter.

The three PV systems:
"RV Building" first install about 2011
       41 Enphase microinverters.  40 working, one dead

"Guest House", aka "PV Shed", aka "Big Barn" first install about 2014
       57 Enphase including 39 converted from SolarBridge microinverters which were orphaned by the manufacturer.

"House" first install about 2015
        27 Enphase plus 26 on a string inverter
        This meter is due to soon receive a Tesla "PowerWall" battery which should allow "grid down" operation.

So, right now, I have a total of  40 + 57 + 53 working panels.  150.  Maybe 37kw.

Each of the above three installations has portions that were professionally installed on roofs at a cost of around $4/watt.  I've installed all ground mount portions at a cost of less than $1/watt.  All panels are around 250 watts.  That is, they might produce 250 watts under ideal conditions.  In practice, they produce no more than about 200 watts.  That peak production lasts only a few mid-day hours on sunny days.

The "pay back" period for the professionally installed portions are 8-10 years.  That is, after 8-10 years the value of the power produced has covered the cost.  For self installed, the pay back is 2-3 years.  The "pay back" period is somewhat complicated by the fraction of the energy that is bought by the utility.  If I over produce consistently, I am paid only about $.04/kwh.  Energy that I avoid using from the grid is worth more like $.11/kwh.  Note that the "RV Building" system is now mostly paid.

On average, I over produce on each of the three meters.  But not enough to cover the ~$25 per month per meter connection fee the utility charges.  On average, each meter costs me about $10/month.

With daily BlueBonnet data, I keep track of meters in danger of under producing and shift my car charging to meters that are clearly over producing.  I can also adjust demand with two water wells, one on the "RV Building" meter and one on the "Big Barn" meter.  The "Big Barn" meter supports some seasonal cooling which is a fairly large load.

All current PV is "grid tie" which means when the grid goes down, so does my local production.  I expect soon to be experimenting with "islanding" using the PowerWall; the PowerWall will allow local PV production while the grid is down.  With a reliable grid, such islanding is economically unattractive.







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