Solar PV doesnt seem to be reducing my bills!?

[Doing it for the kids]

So last month my 2 x 25kw PV's produced 1411 kwh.

In the same month we purchased 6601 kwh from the grid.

Almost all our circuits are metered, a few containers with a light in are not. the total sum of used units was 6603 kwh by all the sub meters - I can live with the difference.

most of our consumption is used during day light (working) hours.

this to me suggests that something is amiss. I would have expected my grid purchase to be less than metered amount by maybe 40 - 60% of my PV output - perhaps a gird purchase of 5250 kwh.

what could be wrong?

1) - the meters are not working / something is not being metered that's using a fair chunk (1000 kwh / month!?)
2) - the farm is not getting the right to us the home produced PV before its exported?

Its bugging me and I really want to fix it! at 16.09 p / kwh its also not earning me maybe £113 pcm but a lot more come the summer.

TYIA

@akaPABLO01
@Exfarmer

 

[Exfarmer]

So you have two systems? They are on independent circuits feeding into two import /export meters?
Or is it effectively 1, 50 kw array, split say on 2 buildings? Feeding into one meter?
What is the main use? Obviously lighting last month would not have had much draw, so we guess it is either motors or heating.
Are you heating water?
Have you got systems set up for night use, because you have day night tarriff.
Remember that in February nearly all production would be in the hours 11- 2 . However good this month was, it was huge for us in relative terms.
Do staff clock off for lunch say 12-1 meaning no use at peak.
Lots of questions hope they are not too intrusive, but you needto know all to provide good answers.

 

[e3120]

Certainly seems unexpected. Could you do us a simple single line drawing of the setup showing the various meters? Is there export metering as you're >30kW?

 

[Deereone]

The amount you produce is metered as though you were exporting it all. The amount you use is metered as though you were buying it all.

 

[Exfarmer]

one serious point. last month we did nearly double your output! I believe you are in Warrington and I am in Suffolk which may account for it. However it may be worth posting last years production.

 

[rollestonpark]

We had our main electric meter changed a couple of years ago (long story).
But the meter we had before that, used to measure the consumption on each phase and charge accordingly.
Thus in my case:
I had 1 phase with a much bigger draw than the rest.
This meant I was exporting on 2 phases and importing on the other.
The import price might be 16p (lets say)
Export (6 7 or 8p maybe)
This resulted in me paying the difference.
I tried hard to re-balance the phases, with some success.

My new meter doesn't do this. It's import export is calculated across the phases as a whole.
This could be what's happening to you.

On a lot of meters you can press the button on the front to see what your draw is on each phase at a moment in time.

Or of course it could be something else to do with time of day, such as if your buying electric at market rate, then the price changes every half an hour.
So if your drawing a lot of power at the 'wrong' time of day, this will be expensive power, at a time when your export is not covering your load.

Chris

 

[Badshot]

Surely the only way to know if the solar is reducing use is to compare it to previous years usage, assuming its fairly constant.

My partner can't understand why we still get bills at the grainstore.

Explaining that we put in a 10kw system that should generate £5k annually in fit, to cancel out our £5k annual bill, is beyond his understanding, he thinks it should run the fans meaning no bills,, 2x 30kw fans.
He never will get it.

 

[akaPABLO01]

According to your figures 100% of your solar was used on site and I expect your sub meter registered solar usage with grid supply. So, I would think your bill should have another 1400 units on if you didn’t have solar. The sub meters are the question, do they only measure usage for that unit, or are they official network meters on another supply?

Then get yourself a 3-phase owl, make sure you can get the correct size CTs to measure export?

I just think 100% solar was used.

 

[Exfarmer]

According to your figures 100% of your solar was used on site and I expect your sub meter registered solar usage with grid supply. So, I would think your bill should have another 1400 units on if you didn’t have solar. The sub meters are the question, do they only measure usage for that unit, or are they official network meters on another supply?

Then get yourself a 3-phase owl, make sure you can get the correct size CTs to measure export?

I just think 100% solar was used.

of course if the Arrays feed back through those sub meters then Pablo has hit the nail on the head.
if you are using sub meters to charge tenants then some may be getting a very good deal!

 

[Doing it for the kids]

thanks both. I have had this debate with SSE before. I have just had 2 new meters (off peaks and on peak) fitted so only now can I start this comparisons.

two roof top mounts, actually that's wrong, its 4 (2 on other farm!) but they all feed back to one FIT meter reading. as far as I am aware, they should both feed in to the grid but if I need power then they should supply me, excess then goes back out. I have not fitted export meters because my sums suggested there was no cost benefit given how much we use (or should be!) main use is a number of commercial units and a biomass boiler.

1. The boiler only used 689 kwh.
2. one has a production warehouse, 904 kwh
3. car repairs, 1068 with a small heater in the office.
4. One is mostly an office with electric heating in much of it, 2174 kwh
5. one has a lot of pumps and small porta cabin, all day time use - 1566 kwh
6. last is a porta cabin office and pressure washer - 201kwh

No HW heating. the off peak meter is used for Grain stores only. The one peak is for the whole farm. staff hours remain quite static.

I suspect its the bulk of the heating in the 2174 kwh unit above that's plundering power at night. it will be interesting to see how this develops as more PV is produced during the day?

 

[Exfarmer]

Many import meters also will register the export it would be worth checking this. if you get the meter make and model it is very easy to see on line if this is the case, assuming you are not already doing this

 

[Doing it for the kids]

According to your figures 100% of your solar was used on site and I expect your sub meter registered solar usage with grid supply. So, I would think your bill should have another 1400 units on if you didn’t have solar. The sub meters are the question, do they only measure usage for that unit, or are they official network meters on another supply?

Then get yourself a 3-phase owl, make sure you can get the correct size CTs to measure export?

I just think 100% solar was used.

of course if the Arrays feed back through those sub meters then Pablo has hit the nail on the head.
if you are using sub meters to charge tenants then some may be getting a very good deal!

good points (as usual from you guys!)

the main cable supplies are metered in their units. The PV all feeds back to the main control room to FIT meter. there should be no cross over before the main control room.

I wonder if the PV output has been installed 'after' the incoming feed (so it doesn't get a chance to be used) but from what I can see in there it does not.

I am not sure I can agree on the 'using 100%' of my pv on site.

ultimately if that was the case my usage from the grid should surely have been 6603 - 1411 = 5192 kwh. we instead bought 6601 so 1409 out?

 

[Exfarmer]

we assume that the new meters have been fitted the right side of the array feed in ?

if you have 4 arrays in different locations, you must have 4 FIT meters surely?

 

[Doing it for the kids]

Many import meters also will register the export it would be worth checking this. if you get the meter make and model it is very easy to see on line if this is the case, assuming you are not already doing this

the new meters are complex, I need to have a play with them. that would also shed light on this!

 

[Doing it for the kids]

we assume that the new meters have been fitted the right side of the array feed in ?

if you have 4 arrays in different locations, you must have 4 FIT meters surely?

no they all feed back from the 4 invertors to the main meter via 4 separate cables.

 

[Exfarmer]

good points (as usual from you guys!)

the main cable supplies are metered in their units. The PV all feeds back to the main control room to FIT meter. there should be no cross over before the main control room.

I wonder if the PV output has been installed 'after' the incoming feed (so it doesn't get a chance to be used) but from what I can see in there it does not.

I am not sure I can agree on the 'using 100%' of my pv on site.

ultimately if that was the case my usage from the grid should surely have been 6603 - 1411 = 5192 kwh. we instead bought 6601 so 1409 out?

The PV feed in , must be installed after the import meters
can you post a picture of the meters please

 

[Doing it for the kids]

off peak has the seasonal meter with it. I have to PV meters, one is FITs, one is Smart meter

 

[ifindoubtflatout]

Last month Feb my 8 kw system on my house did just shy of 600KWh total for the month

So that would mean equivalent to 3750 kWh on your 50kw system
Presuming all things being equal

I’m in Durham

So last month my 2 x 25kw PV's produced 1411 kwh.

In the same month we purchased 6601 kwh from the grid.

Almost all our circuits are metered, a few containers with a light in are not. the total sum of used units was 6603 kwh by all the sub meters - I can live with the difference.

most of our consumption is used during day light (working) hours.

this to me suggests that something is amiss. I would have expected my grid purchase to be less than metered amount by maybe 40 - 60% of my PV output - perhaps a gird purchase of 5250 kwh.

what could be wrong?

1) - the meters are not working / something is not being metered that's using a fair chunk (1000 kwh / month!?)
2) - the farm is not getting the right to us the home produced PV before its exported?

Its bugging me and I really want to fix it! at 16.09 p / kwh its also not earning me maybe £113 pcm but a lot more come the summer.

TYIA

@akaPABLO01
@Exfarmer

 

[akaPABLO01]

So last month my 2 x 25kw PV's produced 1411 kwh.

In the same month we purchased 6601 kwh from the grid.

Almost all our circuits are metered, a few containers with a light in are not. the total sum of used units was 6603 kwh by all the sub meters - I can live with the difference.

most of our consumption is used during day light (working) hours.

this to me suggests that something is amiss. I would have expected my grid purchase to be less than metered amount by maybe 40 - 60% of my PV output - perhaps a gird purchase of 5250 kwh.

what could be wrong?

1) - the meters are not working / something is not being metered that's using a fair chunk (1000 kwh / month!?)
2) - the farm is not getting the right to us the home produced PV before its exported?

Its bugging me and I really want to fix it! at 16.09 p / kwh its also not earning me maybe £113 pcm but a lot more come the summer.

TYIA

@akaPABLO01
@Exfarmer

So what was the reading on the main meter(s) if all the sub meter read your purchased electricity?

 

[Doing it for the kids]

Meter read given to them was 6601's worth of usage that passed through their meter for Feb.