New Grid Connection

[charlieroper]

Firstly I'd like to start by saying I have read a number of the other forums covering this topic which have been very useful but I'm hoping for some specific advice on the particular circumstances we have on site. 

We are converting some old stone barns into a new home which will have PV panels, MVHR, ASHP and EV charger. Our DNO (Northern Powergrid) have told us we need a new connection and that this will require "work to our high voltage network" so requires an initial £800 design fee. Before they come on site I'm trying to get my head  around what is actually required so have drawn a schematic below, which is very basic but hopefully conveys the salient points.

 

 

 

Power comes in over the 2 phase high voltage (HV lines, 2 cables, I think that means 11kV) to the transformer about 100m from the house. This is a 15kVA transformer which connects to the low voltage lines (230V) which connect to the cottage up the hill (on our site) and 3 buildings (2x cottages and 1x small pastoral farm) over the road. All of the lines and poles etc are on our land. My understanding of what needs to happen is this: the newly converted farm buildings will need their own LV connection (currently comes off the cottage as shown by the dotted line) and given the increased power demands from the converted barns the existing transformer needs to be upgraded.

 

My questions are as follows:

What capacity should the transformer be? Given 15kVA has been fine for the existing setup (total of 3 cottages and a farm), I would assume that upgrading to 50kVA would be more than sufficient however if we want all houses to have their own 80A circuit then at most you would need a 100kVA transformer (5 circuits x  80A x 230V = 92kVA). Given realistic load demands this is very conservative but if I have understood correctly that is a realistic worst case scenario.

Does the 2 phase (2 cable) HV line need upgrading? My hope is that it wont but I have no idea here. The closest 3 phase (from which our 2 phase branches off) is probably 400m away.

Does the LV cable coming from the transformer need upgrading? Again I have no idea here. 

Can the connection for the new buildings come from the existing pole? This I imagine also ties into the question above but can we connect from that pole to the house by way of underground cables?

Sorry for such a long post but I would be so grateful for the thoughts of those more experienced than me!

[garrymartin]

32 minutes ago, charlieroper said:

What capacity should the transformer be? DNO will work this out based on your supply requirements. If an upgrade is required, it will be at their cost

Does the 2 phase (2 cable) HV line need upgrading? Again, the DNO will work this out, and if anything needs to change, it will be at their cost

Does the LV cable coming from the transformer need upgrading? DNO will advise. It sounds like you will just need a new supply cable to the converted buildings. 

Can the connection for the new buildings come from the existing pole? The DNO will advise on the best route. There are regulations relating to cable heights etc., so they may suggest an underground route, especially if the existing cables may be damaged by construction work. If you're lucky, they may want to put it all underground at their cost, but you'd need to be very lucky for this one... But you do own the land, so it might be something to consider...

 

 

See comments above, but also check out 

for some information on how the charging structure for connections changed from the 1st April 2023 and the differences between reinforcement assets (things the DNO pay for) and extension assets (your connection that you pay for).

[charlieroper]

Thanks @garrymartin

 

Perfect timing as the DNO called me half an hour ago and you are bang on! They think the transformer upgrade will be their expense so we just need to pay for the new connection and dig the underground trench from the final pole to the new house which is through a flat field which is a great result. 

Annoying that I have to pay £800 for them to confirm what I already knew but frankly I'm so relieved I don't have to pay for HV/transformer works that I'll take it!

[charlieroper]

Update on this - we ended up paying £2800 to Northern Powergrid for the work to upgrade the transformer and install a new connection into a kiosk we put in next to the existing pole. We then sorted the connection to the house ourselves which saved us something like £5k.

[Roger440]

Late to the party on this.

 

I got a quote for a conection , close to £20k from pole in my field. It was 3 months PRIOR to the change. They were charging me for a new double pole and transformer.

 

Thanks for the posts and links. Ive gone back to challenge that.

[Roger440]

Back again. National Grid say no on the following basis:

 

"As per National Grid current policy; for reinforcement concerning three-phase upgrades :-Where a customer requests a 3 phase connection and it is necessary to add a third conductor*the customer will be required to pay the full cost as it is not considered a shared asset.* includes apparatus/plant etc…"

 

Im unable to locate any document with such words via google.

 

Does anyone have a view please, on if this is worth challenging before i throw in the towel and buy a bigger generator?

[Nickfromwales]

14 hours ago, Roger440 said:

Back again. National Grid say no on the following basis:

 

"As per National Grid current policy; for reinforcement concerning three-phase upgrades :-Where a customer requests a 3 phase connection and it is necessary to add a third conductor*the customer will be required to pay the full cost as it is not considered a shared asset.* includes apparatus/plant etc…"

 

Im unable to locate any document with such words via google.

 

Does anyone have a view please, on if this is worth challenging before i throw in the towel and buy a bigger generator?

What's the cost of buying a genny, and servicing and maintaining, and then replacing it (and buying fuel to run it) going to be vs the chunk they want for a solid, reliable, maintenance-free hookup? Lifetime costs (yours) etc etc.

[Roger440]

On 24/05/2025 at 23:50, Nickfromwales said:

What's the cost of buying a genny, and servicing and maintaining, and then replacing it (and buying fuel to run it) going to be vs the chunk they want for a solid, reliable, maintenance-free hookup? Lifetime costs (yours) etc etc.

 

I can get a decent silenced genny for circa £3-4k. Got batteries. Need a 3 phase invertor. So would be up and running for say £6k, with a lower cost per unit. Thats ignoring any solar i will add. Would service the genny myself.

 

3 phase isnt price capped either, so could go up much more than a regular domestic supply (as it did llast time). Standing charge much higher too.

 

The reality is, it wont get used much overall. The batteries can run the stuff like the ramp. Very short periods of use. The big load will be a new, bigger compressor. I might use that for a decent chunk of a day, then not use it for 3 weeks. So genny run time will be small.

 

My current supply isnt reliable now, never mind in future if Ed gets his way. There is something to be said for my own security of supply, though thats not the driver here as i already have and have used, a small standby genny. Which is great if rather noisy!

 

Just pondering my options as £20k is daft.

 

Before i do anything i need to understand if National Grid are correct, or if i should be challenging it as others here have done?

 

One person on here got it down from £26k to £450!!! So clearly they engage in piss taking in the hope you just stump up!

[ProDave]

@Roger440  What is the cost they are quoting you for a single phase supply?

 

If that is reasonable, then would a good compromise be single phase for most of the time then fire up the genny for the few times you need to run a 3 phase load?

 

What do you have that needs 3 phase?

[Roger440]

34 minutes ago, ProDave said:

@Roger440  What is the cost they are quoting you for a single phase supply?

 

If that is reasonable, then would a good compromise be single phase for most of the time then fire up the genny for the few times you need to run a 3 phase load?

 

What do you have that needs 3 phase?

I already have a single phase supply. Albeit, it's only rated at 60 amp.

 

I just want/need 3 phase in my workshop which is currently fed from the house. There's 3 phase on a pole in my field, 50 feet from the workshop!!! So near, yet so far. 

 

Main loads would be a big compressor, extract fan (big) ramp, bead rolling machine, woodworking thing. If I had 3 phase id be adding a lathe to that at least.  

 

Maybe three croc clips is the answer 😂

Edited Monday at 08:34 by Roger440

[garrymartin]

On 24/05/2025 at 09:02, Roger440 said:

"As per National Grid current policy; for reinforcement concerning three-phase upgrades :-Where a customer requests a 3 phase connection and it is necessary to add a third conductor*the customer will be required to pay the full cost as it is not considered a shared asset.* includes apparatus/plant etc…"

 

1 hour ago, Roger440 said:

There's 3 phase on a pole in my field, 50 feet from the workshop!!! So near, yet so far. 

 

If there is a 3-phase transformer and connection on the pole in your field, why do they need to add a third conductor for reinforcement? Surely there are already three? At the moment, your two quoted comments are contradictory.

 

How many wires connect to the pole and transformer?

 

Here's the one at my plot. You can see that three conductors are available (underground cable, up the pole), but only two are currently connected to a single-phase transformer. So in my case, the replacement of the single-phase transformer with a 3-phase transformer should be a network reinforcement that I am not charged for. The 3-phase cable is already available at the pole.

 

 

[mjc55]

4 hours ago, Roger440 said:

 

I can get a decent silenced genny for circa £3-4k. Got batteries. Need a 3 phase invertor. So would be up and running for say £6k, with a lower cost per unit. Thats ignoring any solar i will add. Would service the genny myself.

 

3 phase isnt price capped either, so could go up much more than a regular domestic supply (as it did llast time). Standing charge much higher too.

 

The reality is, it wont get used much overall. The batteries can run the stuff like the ramp. Very short periods of use. The big load will be a new, bigger compressor. I might use that for a decent chunk of a day, then not use it for 3 weeks. So genny run time will be small.

 

My current supply isnt reliable now, never mind in future if Ed gets his way. There is something to be said for my own security of supply, though thats not the driver here as i already have and have used, a small standby genny. Which is great if rather noisy!

 

Just pondering my options as £20k is daft.

 

Before i do anything i need to understand if National Grid are correct, or if i should be challenging it as others here have done?

 

One person on here got it down from £26k to £450!!! So clearly they engage in piss taking in the hope you just stump up!

 

Didn't know this (3 phase costs highlighted above).  Just to clarify, are you saying ongoing electricity costs (unit cost & standing charge) will be higher for us as it will be a 3 phase connection, or am I misunderstanding what you are saying?

[Roger440]

1 hour ago, garrymartin said:

 

 

If there is a 3-phase transformer and connection on the pole in your field, why do they need to add a third conductor for reinforcement? Surely there are already three? At the moment, your two quoted comments are contradictory.

 

How many wires connect to the pole and transformer?

 

Here's the one at my plot. You can see that three conductors are available (underground cable, up the pole), but only two are currently connected to a single-phase transformer. So in my case, the replacement of the single-phase transformer with a 3-phase transformer should be a network reinforcement that I am not charged for. The 3-phase cable is already available at the pole.

 

 

There argument is that the transformer is a "conductor" as defined in the documents. Which I'm currently unable to find. 

 

Which sounds like weasel words hence I really want to see the document that spells this out.

 

Ive requested that or a link to it 

[Roger440]

4 minutes ago, mjc55 said:

 

Didn't know this (3 phase costs highlighted above).  Just to clarify, are you saying ongoing electricity costs (unit cost & standing charge) will be higher for us as it will be a 3 phase connection, or am I misunderstanding what you are saying?

You have not misunderstood.

 

I didn't know this either, but googling suggests that's the case. As ever with our ridiculous electricity market, you can't actually find out real numbers unless you make contact with a supplier to get a quote. I think we know how that will go given I don't have a 3 phase supply.

 

Quite why it needs to be a secret, I don't really know ?

 

I don't know anyone with a domestic 3 phase supply to ask. Maybe someone on here can tell us what they are paying.

Edited Monday at 12:02 by Roger440

[mjc55]

I am just in conversation with Southern Electric about our supply, I want to make some changes to the route (slated for install in July as it is coming across a lane) I will ask him about this.  

 

It is shocking (no pun intended!)  if it is more expensive as this has never been mentioned.

[Roger440]

11 minutes ago, mjc55 said:

I am just in conversation with Southern Electric about our supply, I want to make some changes to the route (slated for install in July as it is coming across a lane) I will ask him about this.  

 

It is shocking (no pun intended!)  if it is more expensive as this has never been mentioned.

Do let us know how you get on please.

[garrymartin]

43 minutes ago, Roger440 said:

There argument is that the transformer is a "conductor" as defined in the documents. Which I'm currently unable to find.

 

Rubbish. A conductor is the overhead or underground cable.

 

5 hours ago, Roger440 said:

3 phase isnt price capped either, so could go up much more than a regular domestic supply (as it did llast time). Standing charge much higher too.

 

 

Also not true.

 

Doesn't matter whether it is single-phase or three-phase. What matters is that it is a residential connection. Standing charges are the same for single-phase and for three-phase on residential connections.

 

I think you may be confusing conversations about non-residential connections, i.e. three-phase for businesses.

[SBMS]

1 hour ago, Roger440 said:

You have not misunderstood.

 

I didn't know this either, but googling suggests that's the case. As ever with our ridiculous electricity market, you can't actually find out real numbers unless you make contact with a supplier to get a quote. I think we know how that will go given I don't have a 3 phase supply.

 

Quite why it needs to be a secret, I don't really know ?

 

I don't know anyone with a domestic 3 phase supply to ask. Maybe someone on here can tell us what they are paying.

We requested 3 phase and were told the transformer couldn’t cope so it’d be 10k or so cost for us to foot for the transformer upgrade. They also offered us an alternative though which was a 40kva connection (3x60 amp) whereas they normally offered 55kva (3x80amp). 
 

Is there sufficient capacity for a 40kva connection?  

[garrymartin]

16 minutes ago, SBMS said:

We requested 3 phase and were told the transformer couldn’t cope so it’d be 10k or so cost for us to foot for the transformer upgrade. They also offered us an alternative though which was a 40kva connection (3x60 amp) whereas they normally offered 55kva (3x80amp).

Possibly before the latest OFGEM changes to clarify cost apportionment between network reinforcement versus connection.

 

However, at least for National Grid (ex. Western Power), single-phase is 80A standard now (they will only provide 100A in very exceptional circumstances), and three-phase is 3x60A.

[SBMS]

45 minutes ago, garrymartin said:

Possibly before the latest OFGEM changes to clarify cost apportionment between network reinforcement versus connection.

 

However, at least for National Grid (ex. Western Power), single-phase is 80A standard now (they will only provide 100A in very exceptional circumstances), and three-phase is 3x60A.

Sounds like we got a result then!

[Roger440]

2 hours ago, garrymartin said:

 

Rubbish. A conductor is the overhead or underground cable.

 

 

Also not true.

 

Doesn't matter whether it is single-phase or three-phase. What matters is that it is a residential connection. Standing charges are the same for single-phase and for three-phase on residential connections.

 

I think you may be confusing conversations about non-residential connections, i.e. three-phase for businesses.

 

Id like to agree its rubbish. They "claim" "apparatus and plant" is included in the scope of "conductor" as per my earlier post. Their words, not mine.

 

As i said, im awaiting the actual documents.

 

I hope you are correct re the connection. Ive also sought clarification if the quoted 3 phase connection is in addition to the existing single phase, or a replacement for it. Though id not thought about it before, if it just feeds the workshop, it could be deemed as non- resedential. Maybe. Who decides? If it feeds the workshop which then fed the house, does that matter? Is it still residential?

 

Though it is a "workshop" its NOT a business, its just for my hobbies and domestic use. Use "incidental to the enjoyment of the main dwelling house" to use the correct phrase.

 

Getting a clear understanding seems "difficult". Its essential its clear before i do anything. 

[Roger440]

5 hours ago, garrymartin said:

 

 

If there is a 3-phase transformer and connection on the pole in your field, why do they need to add a third conductor for reinforcement? Surely there are already three? At the moment, your two quoted comments are contradictory.

 

How many wires connect to the pole and transformer?

 

Here's the one at my plot. You can see that three conductors are available (underground cable, up the pole), but only two are currently connected to a single-phase transformer. So in my case, the replacement of the single-phase transformer with a 3-phase transformer should be a network reinforcement that I am not charged for. The 3-phase cable is already available at the pole.

 

 

 

For clarity, my circumstances at the pole are identical to yours.

 

Have National grid agreed to upgrade to 3 phase and not charge you for the transformer?

 

[garrymartin]

10 minutes ago, Roger440 said:

Ive also sought clarification if the quoted 3 phase connection is in addition to the existing single phase, or a replacement for it. Though id not thought about it before, if it just feeds the workshop, it could be deemed as non- resedential. Maybe. Who decides? If it feeds the workshop which then fed the house, does that matter? Is it still residential?

You need to clarify this with them. I would suggest it is best to get your current connection upgraded, but only you can decide the best course of action. If it is a second connection, then I'm not sure how you would be charged and whether you are allowed two residential connections for a single dwelling.

 

9 minutes ago, Roger440 said:

Have National grid agreed to upgrade to 3 phase and not charge you for the transformer?

Not at that stage. Still at the planning appeal stage. But my expectation based on the new OFGEM rules is that the transformer replacement should not be at my cost - it is network reinforcement and a shared asset. Furthermore, it is likely more properties served by the current transformer will want to move to having heat pumps and EV charging; it's not just me that will make use of it.

 

11 minutes ago, Roger440 said:

For clarity, my circumstances at the pole are identical to yours.

Are you the only dwelling served by this transformer? That may change things...

[Roger440]

18 minutes ago, garrymartin said:

You need to clarify this with them. I would suggest it is best to get your current connection upgraded, but only you can decide the best course of action. If it is a second connection, then I'm not sure how you would be charged and whether you are allowed two residential connections for a single dwelling.

 

Not at that stage. Still at the planning appeal stage. But my expectation based on the new OFGEM rules is that the transformer replacement should not be at my cost - it is network reinforcement and a shared asset. Furthermore, it is likely more properties served by the current transformer will want to move to having heat pumps and EV charging; it's not just me that will make use of it.

 

Are you the only dwelling served by this transformer? That may change things...

 

With reference to your last point, im one of only 2 dwellings. Theres no realistic prospect of any more being added.

 

[SteamyTea]

9 hours ago, Roger440 said:

I might use that for a decent chunk of a day, then not use it for 3 weeks. So genny run time will be small

Can you get compressors that run of ICE engines. Had one on the dive boat back in '72, so probably still get them.