Increasing my electric service

snout71

My home is an old Georgian 5 bedroom house with a 2nd 3 bedroom house located in same property. 

My electrician told me a while ago that I am close to maxing out my board
i want to increase my capacity, I believe I have 100a (though there is a 125a fuse (?) as I want to add a 2nd 6kw solar set up with batteries and maybe even add heat pump(s) 
I believe I can ask for a 2nd 100a service from western power is this right? What sort of cost am I looking at? Do I really need a 2nd line? I have so many questions I am hoping to gain some clarity here

Robin9

Don't understand the ref to 125a.  The company's service termination may be rated at 100a but ii is often down fused to 80 or even 60amps.  

Are you saying that there are two properties involved ? Are you the consumer in both ?   Only one meter ?

What is your actual annual consumption ?

snout71

Since April of this year I have used 13,000 kWh. Not entirely sure how to explain but there seems to be a 125a fuse, then along the line there’s a 100a, then a 100a/80a/60a. The 2nd house/bbq area seems to have a 60a feed. Maybe these pictures will help. 

snout71

Yes two properties, one meter, there’s also several outbuildings

snout71

If it helps the layout looks like this

Qyburn

That looks like your supply fuse is 80A.

Aside from that, how much solar do you have at the moment, and have you asked the DNO whether an extra 6kW could be accommodated?  Our DNO only permitted 7kW total with 4kW export, but the limiting factor in our case is the length (76m) and size (25sq.mm) of the supply cable from our transformer.

Regarding upgrading your supply, as far as I'm aware the next step from 100A would be to three phase. But this should be confirmed with the DNO. It may be that the additional 100A that you speak about would be a completely separate supply, and all you gear would have to be connected to one or the other but not both.

Robin9

It would be most unusual to run a second cable into a property - that would result in a second point of isolation which I don't think the regs permit.

The solution would be a completely new three phase cable and disconnect the old one. You may need three phase for a heat pump - that would well be rated at 40kW (and cost a fortune)

snout71

Qyburn said:

That looks like your supply fuse is 80A.

Aside from that, how much solar do you have at the moment, and have you asked the DNO whether an extra 6kW could be accommodated?  Our DNO only permitted 7kW total with 4kW export, but the limiting factor in our case is the length (76m) and size (25sq.mm) of the supply cable from our transformer.

Regarding upgrading your supply, as far as I'm aware the next step from 100A would be to three phase. But this should be confirmed with the DNO. It may be that the additional 100A that you speak about would be a completely separate supply, and all you gear would have to be connected to one or the other but not both.

Currently I have a 6kw system (Solar and inverter) export is 5kw I believe. 

I almost upgraded to 3 phase last year but was quoted £11k to do the job by western power, should have been 4K but yup they would have to apply to two councils to close one lane of a dual carriageway and could only carry the work out on a Sunday which dramatically increased the cost. Looks like I might not have any choice, but I would need to upgrade the DNO if possible

Ectophile

Your main supply is only 80A according to the fuseholder.  But if you currently have 6KW of generation, and you want to up that to 12KW, then that's still only 52A.  Anything you generate subtracts from what you draw from the mains.

If you are currently limited to 4KW export, then that will be a decision that the DNO made after looking not just at your supply, but at everything else on the local transformer.  Maybe too many of your neighbours have solar too.

As for upgrading your supply, the DNO may offer you an upgrade to 100A at no cost, by swapping the fuse.  But that may not increase the amount you are allowed to export.  And they may say "no" because the local transformer couldn't handle it.

They may be able to offer a three phase supply, if you pay to replace the wiring back to the electricity main.  Or they may not be able to.

Worst case, the DNO will offer to uprate the transformer, and all the wiring from the transformer to your home.  All at your expense, of course.  That could run into tens of thousands of pounds.

doodling

Hi,

The DNO (National Grid) does not offer an upgrade path beyond 80A for single phase supplies, the next step up would be a three phase supply.  That would be rated at 60A per phase but in reality if you need more you could probably get 100A per phase if you needed it.

If the DNO has specified a maximum export of less than 18kW then that will be less to do with your supply arrangements but more related to their wider network in your area.  If you want more export then an upgrade to three phase is pretty much the only solution (and would probably offer you three times the export you currently have).

With respect to import, what makes the electrician say that you are reaching the limit of your supply?  I would be asking for evidence if that is the driving force for a supply upgrade.  If you have access to half hourly smart meter data then using more than 9kWh in any half hour period would be indicative that you are near the limit.

You would need significant demand to justify going beyond 80A.  A single heat pump plus a single electric car charger won't justify it in most cases.

Scot_39

Your main incoming fuse is labelled 80A - which is now the current standard for single phase supply.

And does itself look fairly modern.  So may have been upgraded recently - perhaps at same time as meter - if old was getting dubious.

So the 80A - plus any short term overload - e.g the 100A for 4 hours quoted in NG link below - is your current nominal max incoming limit.

80A at 230V = 18.4 kW.

100A at 230V = 23 kW

I have a 100A fuse - andmy electric shower, HW immersion and 3 NSH can pull 22kW - would be over the new limit - but as the showere never runs for 4 hours - wouldnt be a problem.

And the next stage is 3 phase 60A according to the NG decision notice - some here might be able to tell you about their metering arrangement and tariff - as will have gone 3 phase in similar properties - e.g. to move to ASHP heating.

https://www.nationalgrid.co.uk/downloads-view-reciteme/633928

But also says two single phases at 80A are still a suported option - I guess on those already with 2 supply lines.