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.