This is a wiki Anyone can contribute, therefore we don't vouch for its accuracy.

# VII.b Electricity grid distribution costs

This includes:

It does not include electricity generation or end use. Transmission costs from power stations to the grid are assumed to be part of the power station costs. This includes the cost of cabling offshore wind, wave and tidal.

It does not include the cost of interconnection with other countries. This is assumed to be part of VII.a Electricity imports Costs and of VII.c Storage, demand shifting, interconnection Costs.

Gas distribution costs are covered as part of XVI.a Fossil fuel transfers Costs.

## Technical Assumptions

The electricity grid is modelled on sheet VII.b of the excel model.

It has a single technical assumption: that the grid loses 7% of the electricity that is fed into it.

## Costs methodology

The electricity grid is assumed to be sized so as to be able to carry the peak generating capacity.

The cost of the grid is assumed to increase linearly as a function of this generating capacity. See:

It is assumed that 1/20th of the capital cost of the grid would need to be invested each year to maintain its performance.

Where relevant for conversion, it has been assumed:

• That The GB transmission grid consists of around 25,000 kilometres of high voltage overhead lines (the national grid) and 800,000 kilometres of overhead lines and underground cables (the regional distribution networks).[1]
• That the grid is currently sized to carry 77 GW of capacity.

### Methodology concerns

#### Grid sizing

By sizing the grid to carry peak generating capacity we may be over-sizing. Is this significant?

Transmission: If peak generating capacity includes intermittent plant such as wind then most probably. It may be better to give intermittent plant a capacity value of say 10% and then use this to determine peak generating capacity or alternatively increase the transmission grid capacity in proportion to the increase in peak demand.

Distribution It would be better to size distribution systems in proportion to changes in in demand.

#### Relationship between cost and size

Is a linear growth with capacity a reasonable starting point?

#### Lifespan of the grid

Some grid assets have very long lifespans, and there are expected to be peaks and troughs in replacement rates. Do we need to model this more carefully?

#### Consistency of geography

Are we sure we are correctly capturing Scottish costs?

Are we sure we are correctly capturing Northern Ireland costs?