solar grid tie/meter electrical questions (UK)

[jimmyhackers]

i currently have 2000w of panels going to a grid tie inverter....this feeds a seperate WH meter that we read off the number and tell the electric company and they reimburse us for our solar energy.

this is seperate to our electricity bill which we get still charged for on the WH number on our main meter.

After the solar meter it feeds into our fuse breaker box. which is pre our main electric meter.

my question is.....does the grid tie inveter, when its pumping juice into the system....slow or stop our main electric meter, or at least reduce our apparent electricty usage/cost?

i know the new fancy digital meter we have wont run in reverse "annoyingly", but im wondering if i get a double whammy on my solar setup or not?

thanks in advance.

 

[jimmyhackers]

been thinking....maybe i should ask a different way.

say my house load is 500w, and my gridtie solar is pumping 1000w into the grid.

what percentage of my house load is coming from the grid, and my grid tie system?

 

[bananu7]

my question is.....does the grid tie inveter, when its pumping juice into the system....slow or stop our main electric meter, or at least reduce our apparent electricty usage/cost?

Most likely not. It's hard to tell without specifics, but what you're describing is a scenario where you effectively have two separate systems: consumption and production. You consume from the grid and get billed from the full amount. Additionally, you produce some back into the grid and you get somewhat reimbursed for that. Those two can, AFAICT, run completely separate from each other.

Personally I think those setup are suboptimal, as they rely 100% on the energy company policies for production. Hybrid inverters, where you run both the PV line and the grid line through the inverter, allow actual auto-consumption and operation in island mode. This means that the inverter will present as no load or positive input if the PV setup can satisfy the consumption requirements. This requires a single meter that can handle such a device, though.

 

[Hillhater]

i currently have 2000w of panels going to a grid tie inverter....this feeds a seperate WH meter that we read off the number and tell the electric company and they reimburse us for our solar energy.

Really ?, ..they trust you to tell them how much to pay !
That sounds like a very unique set up. Most grid tied RT solar systems i know of just have one common meter that totals a “Net” supply figure ,..either +ve or -ve,…
For us, these “smart meters” are manditory for RT solar installations.

 

[E-HP]

this is seperate to our electricity bill which we get still charged for on the WH number on our main meter.

After the solar meter it feeds into our fuse breaker box. which is pre our main electric meter.

Here's a few questions.
If there is a power outage, does your solar still power your house?
On the bill/statement, are you charged at the same rate as you are paid for energy?
By pre main meter, do you mean the inverter circuit operates through a breaker on the panel, so the connection is on the house side of the meter? or does pre mean on the grid side of the meter?

If they call it a grid tie inverter, it implies that power from the inverter is going directly to the electrical grid. But, if it's going through the meter (connected on the house side), then the output is already being netted against the house load, so the meter would just read less, and you'd be getting credit through a reduced bill, rather than a separate payment for solar contribution. So, the reason for them asking for the read, is likely to support billing.

As crazy as it sounds, there are even generators tied to the grid that have mom and pop owners (little stream out back with a mini hydro generator, etc.) that are so remote, that installing a secured line for metering is too costly, so they call in their usage, and the utility company goes out and checks once in a while. These are from Jimmy Carter era (PURPA).

In your case, I suspect that the house meter read already "nets" the solar contribution if the solar is connected on the house side of the meter. So the reasons for asking for the meter read is either to pay you less for your solar contribution, or it's a way of charging you more for what you would have used without it (they usually charge you for energy as well as distribution charges to get the energy to your house). They may want to pay you "as though" you were directly tied to the grid at a lower rate, so they can add back the numbers to charge you those other volumetric fees for transmission and distribution based on what you would have used if the solar were grid connected. I'd study your bill carefully to see what volumes and rates apply. It usually works out so they pay you the least and charge you the most. It might even work out that you could minimize how much you pay, if you report zero for the solar.

Also note, there has to be some sort of automatic disconnect switch if your solar is running through your house's connection to the distribution system, since if there were a real outage, the solar needs to separate from the grid so the utility workers don't get electrocuted while fixing the issue. Transformers work both directions.

 

[d8veh]

Here's a few questions.
If there is a power outage, does your solar still power your house?
On the bill/statement, are you charged at the same rate as you are paid for energy?
By pre main meter, do you mean the inverter circuit operates through a breaker on the panel, so the connection is on the house side of the meter? or does pre mean on the grid side of the meter?

If they call it a grid tie inverter, it implies that power from the inverter is going directly to the electrical grid. But, if it's going through the meter (connected on the house side), then the output is already being netted against the house load, so the meter would just read less, and you'd be getting credit through a reduced bill, rather than a separate payment for solar contribution. So, the reason for them asking for the read, is likely to support billing.

As crazy as it sounds, there are even generators tied to the grid that have mom and pop owners (little stream out back with a mini hydro generator, etc.) that are so remote, that installing a secured line for metering is too costly, so they call in their usage, and the utility company goes out and checks once in a while. These are from Jimmy Carter era (PURPA).

In your case, I suspect that the house meter read already "nets" the solar contribution if the solar is connected on the house side of the meter. So the reasons for asking for the meter read is either to pay you less for your solar contribution, or it's a way of charging you more for what you would have used without it (they usually charge you for energy as well as distribution charges to get the energy to your house). They may want to pay you "as though" you were directly tied to the grid at a lower rate, so they can add back the numbers to charge you those other volumetric fees for transmission and distribution based on what you would have used if the solar were grid connected. I'd study your bill carefully to see what volumes and rates apply. It usually works out so they pay you the least and charge you the most. It might even work out that you could minimize how much you pay, if you report zero for the solar.

Also note, there has to be some sort of automatic disconnect switch if your solar is running through your house's connection to the distribution system, since if there were a real outage, the solar needs to separate from the grid so the utility workers don't get electrocuted while fixing the issue. Transformers work both directions.

I have a 5kw UK solar system. In order to get power when the grid is down, I had to install a separate circuit with its own earth rod. You get the choice of on-grid, but all power goes off if the grid goes down; off-grid, where you're completely independent with your own earth rod; or two independent circuits, where your solar and/or batteries can still supply when the grid goes down, but then you have to shift everything to the off-grid sockets.

To answer OP's question, it's difficult to say without knowing the exact installation. In most cases, the inverter is smart enough to do all the sums. when your solar is making power, it's used to power your house as much as it can. Any surplus is tipped into the grid, and any deficit is taken from the grid. Your export meter should be only measuring the surplus that you put into the grid.

I have two meters. My own measures export to the grid and was part of the solar installation. I also have a smart meter, that I think is a SMETS1 with software upgrade or something like that. It displays usage and export. Initially EDF couldn't read the export, so I had to give them the readings to get the credit. Now they've upgraded their system, so they can get it direct and bill me accordingly. I think export was like a separate department before because they always had to transfer meto a different phone line to deal with any queries about it, but now it's all integrated.

It's been a great spring for solar. I hope it goes right through the summer. I generated 500kwh last month, and have done 300 already this month. My best month in the previous 2 years was 700 in June.

 

[Hillhater]

My best month in the previous 2 years was 700 in June.

Wow !, i assume that was the total solar generation ?…23 Kwh per day average ?
How much did you feed back to the grid ?

 

[jimmyhackers]

maybe a crude picture done in paint will help you guys understand my setup.


no my solar doesnt power the house during a power outage.
i imagine i would have to put a regular inverter into my house system to trick the grid tie system to work...but its something im not testing anytime soon.
im unsure of actual costs as my father is obtuse and wont tell me exact mounts (bloody parents) ive been told we get paid 50p per kwh in the past for solar, but i am unsure of other amounts.

my real worry is the solar is actually running up my main meter. but again, trying to get my father to cooperate with experiments to find out is like getting blood from a stone.

 

[jimmyhackers]

update, did a little experimenting this afternoon

wifi main meter showed 330ish watts usage. solar meter showed 170 ish watts into grid.

turned off solar, wattage usage jumped to 500ish watts.

seems like we are getting the double whammy. i think i may add a fair few more pannels\inverters to our array

 

[d8veh]

Wow !, i assume that was the total solar generation ?…23 Kwh per day average ?
How much did you feed back to the grid ?

I use about 5kwh per day. That's pretty consistent. I've been getting nearly 30kwh per day from those clear days last week.

 

[Hillhater]

I've been getting nearly 30kwh per day from those clear days last week.

That is really amazing for a 5 kW system in the UK.
I only have a 2.4 kW panel system and on its best days here in sunny Oz only get 7-8 kWh !
Do you have any tracking systems on your panels ?

 

[d8veh]

That is really amazing for a 5 kW system in the UK.
I only have a 2.4 kW panel system and on its best days here in sunny Oz only get 7-8 kWh !
Do you have any tracking systems on your panels ?

You have to understand where I live too. It's the dullest and wettest place in the whole UK. We had some exceptional weather at the beginning of the month, where the skies were crystal clear every day. In April, the sun is lower and the days are shorter than June, but the air is clearer. The weather has gone back to normal now. Here's what I've had in April so far: