Is it ok to have a 8Kw Solar System for home?

Hussein

My brother wants a 8KW Solar system for his property. His roof is big enough and he is a large energy user. He had an energy survey from a solar company and the advisor said that he can only have a 4Kw system because you would need approval for any system bigger than 4kw from your local grid and it would take too long to get approval.

Is the energy surveyor correct?


tia


PS

SailorSam

I don't think the surveyor is right, most showers are a lot more than 4kw.
The biggest restriction on the size of anything you put in whether that be a cooker; a fire; or a shower, is what size cables have you already got.

ChumpusRex

Yes.

The local distribution network operator must give permission to connect a solar system. Up to 4 kW, the permission is pretty much automatic and a tick box, unless the DNO have already said that the local area is overloaded by solar power.

Above 4 kW, they do not usually give permission if you have a normal domestic electricity supply at 240 volts (single phase), as the supply may not be strong enough to absorb the power effectively.

The DNO may agree or they may not, or they may require specific conditions, such as you pay to have the electrical supply upgraded to 415 volts (three phase). The approval can take time as the DNO will need to analyse the effect of your solar system on their grid and decide if any upgrades are needed to accommodate it.

Cardew

Agree 100 with above post#3


In any case the maximum rate of FIT(subsidy) for domestic users is only for a 4kWp system.

Martyn1981

Hussein wrote: »

My brother wants a 8KW Solar system for his property. His roof is big enough and he is a large energy user. He had an energy survey from a solar company and the advisor said that he can only have a 4Kw system because you would need approval for any system bigger than 4kw from your local grid and it would take too long to get approval.

Is the energy surveyor correct?


tia


PS

Are they correct .....yes and no, depends on the install.

Hi by the way.

Ok, here we go, there are no restrictions (other than physical) on how much PV you can install, but the subsidy tariff drops 10% if you go over 4kWp, most UK rooves could only fit 4kWp, and if you want an inverter than can generate (even if only theoretically) more than 3.68kW then you need prior permission from the DNO (district network operator).

Obviously the house connection is fine, typically 23kW (at a nominal 230V), but the DNO has to consider the impact on the neighbouring area, and the sum of other SSEG's (small scale electricity generators).

You say his roof is big enough, which suggests a single aspect install. I point this out as 6kWp spread half East and half West could share a 3.68kW capped inverter without too much capping. [Edit: 5kWp south facing wouldn't lose much pa to capping either. M.]

However, 8kWp all south facing would lose quite a bit to capping if limited to 3.68kW, so logically you'd want to ask to go bigger. As the government has proposed cutting the FiT by 87% in January, then it might be too late to get an answer from the DNO in time. They may answer very fast (yes or no) but their official response times are often something like "upto 6 weeks".

The government review is currently swamped, and they are getting criticised from all sides, even foreign onlookers concerned at the govt's reversal on most of the renewable schemes. So, it's taking longer, and what ever the result will need to sit for 40 days (I think) in Parliament, which I think takes us into mid Jan now.

For more info on rules and regs on going big, have look at section 10 of the FAQs. It's about extensions, but the info is still relevant.

Mart.