System Price
The imbalance cash-out price
What is it?
The System Price is the price at which imbalances are settled in the GB electricity market. If a market participant generates more or consumes less than their contracted position, they are "cashed out" at this price.
Since November 2015, the UK uses a single cash-out price, meaning the System Sell Price (SSP) and System Buy Price (SBP) are calculated as the same value.
Key Points
Unit
£/MWh (GBP per megawatt-hour)
Update Frequency
Every half-hour (48 per day)
Source
Elexon BMRS (official settlement data)
Typical Range
£30-80/MWh (can spike to £1000+ or go negative)
How It's Calculated
The System Price is based on the marginal cost of balancing actions taken by NESO:
- 1NESO accepts bids and offers to balance supply and demand
- 2Balancing actions are tagged (BOAs) with prices
- 3System Price = Volume-weighted average of accepted offers (if system was short) or bids (if long)
Note: The calculation is complex with various adjustments (NIV tagging, reserve scarcity pricing). See the Elexon BSC for full methodology.
When It's Used
Imbalance Settlement
The primary use. If you're a supplier and you contracted to buy 100 MWh but your customers only used 90 MWh, you sell that 10 MWh surplus at the System Sell Price.
PPA Reference Price
Some PPAs use System Price as a settlement index, especially for "as-generated" contracts where the generator sells all output into the balancing market.
Trading Signals
Traders watch System Price closely for arbitrage opportunities. High prices indicate system stress and potential for profitable balancing actions.
API Endpoint
GET /uk/prices/system/latestReturns the most recent system prices including SSP and SBP.
{
"data": [{
"settlement_date": "2024-12-20",
"settlement_period": 28,
"price": 52.34,
"system_sell_price": 51.20,
"system_buy_price": 53.48
}],
"unit": "GBP/MWh"
}