Hi Everyone,

Received quotes back from DNO for New Build, they have come in at over 16k for single phase, 23kVA import capacity with 25kVA transformer or over 23k for 3 phase, 40kVA import capacity with 100kVA transformer.

Both require a post and relevant transformers. Power lines run along one side of our plot so distance isn't a factor.

Our set up will be 12Kw ASHP

21 x 510w solar panels

12Kwh back up battery

Fast charge EV charger

Induction Hob

Small workshop

Usual household appliances etc.

These costs seem excessive, frustration is there is already 3phase to existing barn but we cannot use this to reduce cost according to DNO, their quote to upgrade existing transformer came in more expensive.

My question is, do we go with the single phase or 3 phase given this is our only source of power and we want to future proof as much as possible?

Quote between contestable and non-contestable costs are less than 1k so not sure where savings can be made.

Is the barn yours and on the same site ?

If so I do not understand why you cannot come from there.

Is it worth talking to your electrician?

I had a similar initial quote and quibbled it it came down. Read up on what should and should be chargeable on the no-contestable sometimes some costs of upgrading which should not be charged to the customer are slipped in. There are some good threads here already to assist with this. For the contestable we made some really good savings doing dig and duct ourselves and then finding suitable licensed contractor for cable install and meter works. Ended up paying roughly half. All in.

Not actually finished yet so there could be some surprises.

A 12kw heat pump for a new build is a lot. What's the size of the property? Minimum/regs insulation or a higher standard?

What's the size of the existing 3-phase?

I wouldn't be surprised if your overall energy estimates are pushing the DNO to overspec your needs and you couldn't just get away with sharing the existing supply with no upgrade at all. You have a lot of solar going in and if needed you could likely leverage that + batteries to offset peak demand if it's borderline. Some inverters will have a mode to allow this (ie, it will use power from the battery to limit the overall draw on the utility) and if not then there are plenty of other options if you can redirect some of the 16k into solar stuff.

If the current spec is minimum insulation then bumping that to high spec might cost a few k extra but reduce energy requirements and long term bills.

Not done this myself but DNOs tend to get quite concerned when you say 'workshop' and they tend to want to specify the supply to power everything at once whereas for a hobbyist/one man small business it's unlikely you use more than 2 machines at once.

That sounds very similar to my quote.

Like you, 3 phase was near. In fact 50ft away on my own land.

Unlike Badger Bodger, they point blank refused to budge.

Theres lot of talk about them not being allowed to charge the end user for "upgrades that are required". As i quickly discovered, that statement was largely PR and government spin and only applies in certain very specific circumstances. The book of exemptions from that policy is considerable.

They did confirm had there been 3 houses on the supply, not 2, it would have been just a minor cost. Book of excuses deployed succesfully there.

I didnt go ahead as i have a limited 60a single phase supply any way. Its just means i need to stick with oil for some of my heating requirements and i cant use the 3 phase equipment i wanted to use.

If the barn is yours, i cant see why you cant use that? Its probably on a commercial suply (ie much more expensive) but in my discussions with DNO, they were quite happy to change that to domestic if it was. This would be my line of attack in the first instance.

Thanks everyone for your replies, lets work through them.

FarmerN - Yes barn is ours, the supply running to it is from the adjacent farm who originally owned the barn, we must now separate that supply.

The transformer supplying the farm is 3 phase, 50kVA, I hoped it would be a case of upgrading to 100kVA and running a new cable for us. DNO has quoted for this, however that quote is even higher than a completely new pole and equipment for us, isn't making a lot of sense as existing pole is only about 20 metres away.

BadgerBodger - Our contestables have been priced at less than 1k by DNO so very little wriggle room, the new post will be about 6 mtrs from where our Kiosk will be sited.

Please point me in the right direction regarding threads on this, all advise welcome.

-rick- Had the ASHP provisionally priced by well known, fairly local company and two others, all said around this figure. To be fair this was very early days, we hadn't finalised our method of insulation at that time. As you say this figure needs updating.

Aim is to use approx 300mm Hemp-lime insulation with external insulation wrap. Aiming for near Passivhaus standard without the hassle of certification.

Totally agree about the workshop, I did make it clear it was more hobby use.

The push for 3 phase has been coming from me, primarily. I've spoken with 3 local electricians early on as DNO needed our diversified power requirements, they all shook there head.

Two electricians said 3 phase was the way to go at this stage, given it's our only source of energy and the likely need for fast chargers etc in the future. One said single phase was adequate.

I'm also looking to export back. DNO has said we can export 16amps per phase, doesn't mean a lot to me to be fair. Any advise?

Roger440 - DNO has given reason as to why utilising existing pole nearby is more expensive. "The existing transformer within your neighbour’s land has a service cable connected to it, therefore will not allow for a new connection without further chargeable network augmentation".

I see why you have the problem using the barn. Can't offer any suggestions to that situation. Having the farmer supply you long term is fraught with difficulties.

18 minutes ago, E A West said:

-rick- Had the ASHP provisionally priced by well known, fairly local company and two others, all said around this figure. To be fair this was very early days, we hadn't finalised our method of insulation at that time. As you say this figure needs updating.

Aim is to use approx 300mm Hemp-lime insulation with external insulation wrap. Aiming for near Passivhaus standard without the hassle of certification.

Unless you are building a 500m2 mansion then 12kw is way way too much for that. See other threads on here about heat pumps. A lot of 'very good' installers aren't very good at thinking about low energy homes and just do what they know (which is retrofit on old, inefficient, homes).

Another thing to note is to ensure the calculations provided to the DNO are for the electricity actually used by the heatpump not it's nameplate 12kw (or more likely 6kw or less once you've done the calcs). A heat pump outputting 12kw won't consume more than 6kw unless something is very wrong. DNO would need to know it's soft-start/inverter driven too (though that should be assumed these days its good to check).

18 minutes ago, E A West said:

Totally agree about the workshop, I did make it clear it was more hobby use.

Also worth considering starting current. If they are assuming you have a big 3 phase something or other than doesn't have soft start/inverter drive they will overprovision

18 minutes ago, E A West said:

The push for 3 phase has been coming from me, primarily. I've spoken with 3 local electricians early on as DNO needed our diversified power requirements, they all shook there head.

Two electricians said 3 phase was the way to go at this stage, given it's our only source of energy and the likely need for fast chargers etc in the future. One said single phase was adequate.

I'm also looking to export back. DNO has said we can export 16amps per phase, doesn't mean a lot to me to be fair. Any advise?

I'm sure you could get away with single phase if need be but personally I think 3 phase is the way to go if you can, but not necessarily worth a major cost uplift.

16A per phase is approx 3.7kw per phase. If you have 21 panels at 510W each, that's a total of 10.7kw. So if you have a 3phase supply you would be theoretically able to export your full solar generation without special permission from the DNO. On a single phase supply you'd have to apply for that export and be approved. Having said that if you are getting a new supply anyway I think the point is somewhat moot as they can add restrictions as part of agreeing to provide the new supply.

Edited 5 hours ago5 hr by -rick-

19 minutes ago, -rick- said:

I see why you have the problem using the barn. Can't offer any suggestions to that situation. Having the farmer supply you long term is fraught with difficulties.

Just thought to add, if you have no choice but to get a new supply then there is not much point optimizing what you ask for unless if affects the cost of new supply and I would guess that the DNO might not want to offer a smaller 3-phase transformer (even if they did that might not affect the cost by a huge amount). Still, may be worth exploring if there is an option for a smaller 3 phase transformer and what that impacts.

Edit to add: but a downside of 3phase if having a small overall supply is that balancing the phases becomes harder, which may cause your electrician headaches.

Edited 4 hours ago4 hr by -rick-

I see. So, realistically, the barn route is off the table.

Given my experience with a single connection, i cant see much alternative than to dig deep in the piggy bank.

They will charge you for everything, because the rules allow them to do so. I think its all wrong, its a bit like going to get petrol, and being charged for the pump installation..

By all means challenge it, i suspect it is what it is. I didnt get anywhere at all. When challenged they just referred me to the appropiate documents that confirmed they could indeed charge me for every cost involved.

I'm not sure why you should have a more expensive quote to upgrade the existing transformer - that appears to be classic reinforcement, and I would have expected your costs to only cover your connection, not the transformer upgrade. The second scenario where you are the only person being supplied (single or three-phase), I would expect you to pick up the full cost as they are allowed to pass that on.

It certainly feels like they're using the first quote, which they've presented as being more costly, to get you to accept one of the second quotes. The issue would be that the costs should be mostly with the DNO in the first quote, but they can transfer them all to you if you accept the second.

Ask the DNO for an itemised breakdown of both approaches, making it clear which elements are extension assets, which reinforcement, and what is contestable versus non-contestable work. Ask them to tell you which section of their Connection Charging Methodology justifies each line.

Try submitting a lower demand requirement.

We only have single phase here but when I enquired about our supply they offered me a 12KVA single phase supply at a good price. They said anything more they would have to upgrade the transformer. I accepted. So try say a 24KVA 3 phase supply as your requirement?

The reality is I have the same cable and same 100A DNO fuse as every other house so could draw the full 23KVA. Nobody would even know.