Solar power & AC current direction help, please! - Page 1
Forum section: electronics / general

author: technolaser
author_rank: Newbie
timestamp: June 19, 2025, 09:04:17 am
content: Hi everyone,I understand the basics of electricity but I'm stumped here and hope someone can help me out. All I'm trying to do is lower my bill as electricity is expensive here.I have 3 phase supply to my house and 3 separate sets of solar panels (about 600w each), each with its own grid-tie inverter connected to the 3 phases individually. Nothing huge, max 2 amps (@220) per inverter. I simply want to make sure that I'm not being charged for some of my solar generation, which I suspect is happening. I have a digital, non-smart meter outside the house which according to the manual, can only monitor current flow into the house.I installed current monitors with a toroid on each phase coming into the house. Some experimenting shows the following. If phase A reads 6.5A for example and I turn on the inverter, the current drops to 5A. Great so far. If phase A reads zero and I turn on the inverter, current goes up to 1.5A and the outside meter displays a flashing arrow (pointed right to left). If I'm not drawing anything on that phase, where is the power going? Am I being charged because the meter ticks up, even though the power flow is reversed?I'm thinking of installing 3 power monitors (with WiFi) to show whether power is generated or consumed and how much. Would this show me what's happening?I'd appreciate any input or suggestions for checking.TIA

author: fourtytwo42
author_rank: Super Contributor
timestamp: June 19, 2025, 01:29:53 pm
content: You need to check with your utility and/or publish the make & model of your meter together with a picture (always helps).Some meters consider export to be fraudulent and some charge it as import!I bet our electricity here in the UK is more expensive than yours, after all we are leading the world in climate charges on consumers

author: Siwastaja
author_rank: Super Contributor
timestamp: June 19, 2025, 01:59:20 pm
content: You can't just connect a power plant to the grid. You need a permit, and proper contract with the utility, and at that point they will install bidirectional metering, which is the key component for billing. What exactly are the billing rules and how export is compensated for you can be discussed at that point.Some unidirectional meters indeed register production as consumption, which is a sane thing to do because then it Just Works even if wired up "the opposite way", when you only have consumption.If getting the permit / new bidirectional meter is expensive for you, and you want to work around that on your own, you need to come up with some kind of control system which prevents export (by including its own bidirectional metering; can't be done with current transformers alone, need voltage measurement, and commanding the inverters to stop and/or turn on extra loads) but then it's still a question how quickly it can react and how much it will export anyway due to non-ideality of the system.

author: technolaser
author_rank: Newbie
timestamp: June 19, 2025, 02:10:32 pm
content: The meter says Foetec Reallin E3006-01 (https://www.reallin.com/related-products/three-phase-electricity-meters/three-phase-whole-current-electricity-meter.html). No manual on their website for me to check what the symbols mean. Will post a picture soon."and some charge it as import" is what I'm afraid of! I have no intention of exporting, just hoping to reduce my consumption.I just paid 15p per KWh. How does that compare to yours fourtytwo42?I too want a greener world, but I only wish that some of the money went to genuine impact reduction on the environment, not some virtue signaling fad.Siwastaja - For me to get permission to connect my 1800W of panels to the grid would cost me in the region of $25k. If the meter does register production as consumption I might have to rethink it all. I'm not looking for a perfect system, just that whatever I generate might be used to reduce my consumption. Surely I'm not the only person trying to do this??

author: Siwastaja
author_rank: Super Contributor
timestamp: June 19, 2025, 02:41:36 pm
content: Quote from: technolaser on June 19, 2025, 02:10:32 pmSurely you are not the only one, and therefore I suspect your $25k figure is bogus. Here it is 0EUR, for example. Actual meter cost is around $100 in large volumes (when utility buys it) and replacement work takes 15 minutes, so the real cost of that is in ballpark of $150-250, depending on how well trips between customers are organized.We are in oursecondround of bidirectional meter swaps here. Have had bidirectional metering for basically everyone for 10 years now. No cost to customer, the real $200 cost is amortized to every customer, which if done every 10 years is then around $20/year.Of course, it is possible that for political reasons it is made artificially difficult. If that's the case, then I don't see other options than export limits. That requires that you install an additional bidirectional meter after the utility meter, connect that meter to the inverters (usually with RS485 bus) and configure the inverters to zero export mode. I'm not sure if your microinverters support this, probably not since microinverters are often pretty limited in fundamental features.

author: technolaser
author_rank: Newbie
timestamp: June 20, 2025, 09:56:08 am
content: Thanks for all the input.This is a picture of my meter. Hopefully someone can tell me whether or not it'll charge me when I generate power. This is supplied by the elec company and even if I paid the £130 for a new meter, there's no guarantee that the new one will only charge for consumption. I have no say in what meter they install.Yes, the cost to connect panels to the grid is exorbitant. First I need a special electrical engineer to design the system which has to be approved with planning permission from my local council. Then I have to apply for a permit by the elec company. Once the system is installed I need approval by the council and also the elec company. Each step is a huge amount of money. I pay £0.15 per KWh and if I generate, I get paid slightly less than this.

author: fourtytwo42
author_rank: Super Contributor
timestamp: June 20, 2025, 10:06:35 am
content: Quote from: technolaser on June 19, 2025, 02:10:32 pm44.32p/Kwh last month, makes your eyes water doesn't it!!And they wonder why UK industry is un-competitiveI see what you mean about the chinesium meter site, not much information there.My utility did not know what I was talking about either so the only way I found out was to carefully compare my bill with the meter. Your meter has separate registers for import & export, so when you get your bill compare the utility reading with these registers to see if they are charging you the total or just import.

author: technolaser
author_rank: Newbie
timestamp: June 22, 2025, 07:11:31 am
content: I think 44p is insane!! Maybe covering all farming land in solar panels can reduce that 44pSometimes I wonder about the intelligence of humanity.After doing some experimenting this morning it looks like I have my (unwanted) answer. My meter does tick up no matter whether I'm generating or consuming power. I read the meter, then I made sure everything was off and nobody was in the house to turn something on. I then plugged in 1/3 of my panels and the meter kept rising.I now have to figure out some economical/reasonable way of using the power I can generate. Pity there's no such thing as an AC diode.

author: uer166
author_rank: Super Contributor
timestamp: June 22, 2025, 09:39:10 am
content: Zero export inverters are a relatively standard thing: you put a CT on your drop and the inverter tries to never feed current back to grid (drives it to 0A if you have excess solar).

author: technolaser
author_rank: Newbie
timestamp: June 22, 2025, 10:13:35 am
content: Thanks uer166, I'll look into this.

author: fourtytwo42
author_rank: Super Contributor
timestamp: June 22, 2025, 01:04:59 pm
content: Quote from: technolaser on June 22, 2025, 07:11:31 amUnfortunately that would probably make matters worse! The way the idiot's work is to guarantee a rate per Mwh to the provider (whether it's used or not) that pays for the amortization of capital costs plus a substantial profit, they keep raising the rate till someone bids! Hence on windy days we pay to have wind turbines not generating......Now we have the politically inspired great British energy in charge not only will prices go through the roof but the lights will go out as well, apparently that's progress to a greener and de-industrialized future lols

author: MF-jockey
author_rank: Regular Contributor
timestamp: June 23, 2025, 04:03:45 pm
content: The arrows on your meter indicate exactly what you've already measured. The upper arrow pointing to the right represents your electricity consumption from the grid. The lower arrow pointing to the left represents your feed-in—and this describes a reverse semicircle toward your energy consumption.You'll be charged for your feed-in because the grid operator has to set up balancing energy and possibly storage for this excess energy.

author: technolaser
author_rank: Newbie
timestamp: June 25, 2025, 08:50:59 am
content: Thanks MF-jockey, that icon now makes perfect sense given my actual consumption is about 350KWh per month, and on my last bill I paid for 980KW!Thanks to everyone who helped me wort this out.

author: fourtytwo42
author_rank: Super Contributor
timestamp: June 25, 2025, 09:51:15 am
content: Quote from: technolaser on June 25, 2025, 08:50:59 amOUCHHHHH!!!!!

author: Hr_Satch
author_rank: Contributor
timestamp: June 26, 2025, 09:35:10 pm
content: Hey, hello,I think the most stupid thing our so-called "leaders" could have done,is creating the power delivery feedback thing for money-money-money, . . .The insentive was utmost wrong !Same as The internet was released to inform the general public,however it missed for the most its intended purpose, and is mainly for banter.Solar power is until now one the most effective FREE energy source available nowadays.And what they did was rendering environmental friendly once again into profit, . . .I think, if you really want to be independant, and safe on the energy bills -during summer-is turn the mains inlet switch off- right after the Kwh-counter.That is your part where you are allowed access.However, than ofcourse you need some kind of energy storage, . . .A real concerning governement should invest research on that particular hickup: energy storage.So the guy with its three inverters ? At my country electricity comes always in with three phases,but there is only house hold use on one mono-phase, for most of us, . . .Instead of investing money in three inverters, three split solar panels, etc. . ..Go for mono phase, if you have enough power than, and look out for some means of storage:battery, Hydrogen, ... But disconnect from the grid when it is possible.And if keeping the three phase energy source, try spliting your mains circuits,like one phase for the general lightning, small power outlets for TV, VCR, PC, ...A 2nd phase circuit for a big consumer like laundry washer, and/or clothes dryier, . . .And the 3th one for lets say an electric oven, cookingplates, . . .Or even better, orient your three rows of panels in the three sunny positions: East-South-West.but please refrain from that stupid "I want just my counter to count back"because that is missing the whole point, once again, just for short notice profit.? Why, not creating for ex. a washing machine with a low voltage motor ?So no wastefull energy conversions, most people use and buy inverters for household lightning ? ?Just go for a Low voltage lightning circuit, . . .