Energy · Scope 2
Purchased steam, heat, cooling and CHP
Energy delivered to you by someone else's plant. Each is costed from the fuel or electricity the plant used, so Slate needs to know how efficiently it was made.
On this page you'll learn
- Steam with and without a known fuel
- How chilled water uses the plant's coefficient of performance
- How CHP output is split
- Scope
- 2
- Publishers
- US EPA, UK DEFRA, and your electricity source
- Category codes
steam_hot_water,chilled_water,chp
Steam and hot water
Fuel known (preferred)
The steam delivered is grossed up to the fuel burned using the delivery efficiency, then costed as that fuel through your source chain. EPA recommends this, and it's more accurate.
Fuel unknown
Costed from a published purchased-heat factor: DEFRA's district heat at 0.17529 kg CO₂e/kWh, or EPA Hub Table 7 at 0.2263 kg/kWh.
Watch out
EPA's Table 7 already assumes natural gas at 80% efficiency. Dividing by an efficiency again would under-report by about 20%, so the fuel-unknown path never does. And a UK site used to be costed at EPA's US figure here, 29% too high; it now resolves to DEFRA through the chain like everything else.
Chilled water
- COP
- coefficient of performance, default 4.2
- transmission loss
- default 10%
- COP × (1 − loss)
- 4.2 × 0.9 = 3.78
- Electricity used: 100 ÷ 3.78
- 26.46 MWh
- Costed at
- your grid electricity factor
The electricity goes through your source chain, so a UK chiller is costed on the UK grid, not EPA's eGRID. Absorption chillers are costed from the fuel they burn instead.
Combined heat and power
Electrical output from a CHP plant is costed as electricity through your source chain. Thermal output is costed like steam: from the fuel, divided by the delivery efficiency.
Note
No publisher issues a purchased chilled-water or purchased-CHP factor. DEFRA publishes neither, so these always need the plant's fuel or electricity.