Self-Consumption of PV power: grid tied, no net metering, no batteries

[Ampster]

This would seem to be illegal as they are charging you for using your own energy that would be self consumed without touching their grid.

Your best bet is to not do an interconnect and just work with a grid zero system. You would ONLY ever get self consumption though.

And that would only require a building permit if no interconnection was requested. Just to be clear that also assumes UL approved equipment in order to comply with codes. No permission needed from the POCO since everything is behind the meter. I think that is the workaround that people have used in Hawaii when the POCO was stonewalling them on approvals. I don't know if that is still the case in Hawaii. I do know that is possible in California according to my County Building Department.

[ButchDeal]

I haven't seen an actual wiring diagram, but I've heard back from the installers and they are now agreeing that it's "A". Austin Energy says:

I'm guessing that means that the PV system will be just connected to this meter which measures total production before any of that electricity can be consumed or fed onto the grid. The the existing utility meter still measures total consumption regardless of what the PV system is doing. This is unfortunate and seems unreasonable (see prior example where I would end up paying austin energy for putting 12kWh onto their grid for them) but is the way it is. Boo.

I was hoping it was "A, unless you use a special type of inverter like StorEdge (even without a battery) in which case it would be B" or something.

This would seem to be illegal as they are charging you for using your own energy that would be self consumed without touching their grid.

Your best bet is to not do an interconnect and just work with a grid zero system. You would ONLY ever get self consumption though.

[evolknuj]

I haven't seen an actual wiring diagram, but I've heard back from the installers and they are now agreeing that it's "A". Austin Energy says:

On a wall near your existing utility meter and electric service panel, you will have an additional meter called a PV meter. This measures how much energy your solar system is producing.

I'm guessing that means that the PV system will be just connected to this meter which measures total production before any of that electricity can be consumed or fed onto the grid. The the existing utility meter still measures total consumption regardless of what the PV system is doing. This is unfortunate and seems unreasonable (see prior example where I would end up paying austin energy for putting 12kWh onto their grid for them) but is the way it is. Boo.

I was hoping it was "A, unless you use a special type of inverter like StorEdge (even without a battery) in which case it would be B" or something.

[ButchDeal]

IT is going to depend on how they are measuring the production.

Your comparison to Hawaii is not accurate. They do NOT have a similar schedule at all. Hawaii restricts new applications to ZERO feed in. That means they can not produce ANY more power than they are consuming at any moment. They do get to self consume and basically because of that they get full retail value for the power they generate.

[Ampster]

I am sure someone else will chime in with a similar answer, but the most accurate answer you get will be from a published tariff or rate scheduled approved by the Utilities Commission. No matter the answer you understand from the explanation from your vendor or POCO it is best to verify in writing.

[evolknuj]

Austin Energy is my provider and they do not use net metering. Instead they use VOST to pay solar owners 9.7c/kWh of generated PV while still charging for my total consumption using tiers (it's hot in texas, we often hit the top tier unfortunately). E.g.: https://news.energysage.com/austins-...g-solar-power/

Quote [emphasis added]:
Under a VOST program, a solar power system user still pays for all electricity from the grid, consumed in their home as they did before. Then the utility gives the user a credit for each unit of electricity (expressed in terms of Kilowatt Hours or kWh) produced by the solar energy system whether used onsite or pushed back to the grid.


I'm getting two different answers from installers as to what that means, so I came up with a simple scenario to ask:

It's the last day of August and I've consumed enough already to get into Austin Energy's Tier 5 rate (lets say 15c/kWh after all the extras). It's clear and sunny and my PV is generating 7000w constantly between 9am and 3pm, and my AC is running constantly consuming 5000w for the same 9am-3pm interval. What is the end result for those 6 hours?

A: Austin Energy's meter registers 42kWh of PV (7kW*6h) and I get a $4.07 credit (42kWh*9.7c/kWh). Austin Energy's meter also registers 30kWh of consumption (5kW*6h) and I get a $4.50 charge (30kWh*15c/kWh). In the end, I need to pay AustinEnergy $0.43c for those six hours, even though I was pushing 12kWh more electricity to the grid than I consumed. Boo for the tariff difference and VOST scheme!

B: My AC self-consumes the PV electricity available without it even touching Austin Energy's meter. Austin Energy's meter sees 12kWh of PV ((7kW-5kW)*6h) and I get a $1.16 credit (12kWh*9.7c/kWh). Austin Energy's meter sees zero draw from the grid in those 6 hours, so I get a zero charge. In the end, I get the $1.16 credit for those six hours. Yay for self-consumption!


Lots of simplifying assumptions in there of course, but it's a valid question I think. I think Hawaii is another market that has similar issues, except their prices are often high enough to justify battery storage so even more of their generated power could be self-consumed in the evenings. What's the answer? (I'm double-asking the installers too, and prodding them to ask Austin Energy reps as well).

I don't think it makes any difference to the answer, but I'm looking at either Enphase IQ7 microinverters or SolarEdge string inverters with DC optimizers, panasonic HIT panels, and about 12-15kW roof mounted if/when I pull the trigger.

Thanks!