Scope 2 Purchased Steam & Hot Water Calculator
Compute Scope 2 emissions from purchased steam, hot water, and district heat on both the location-based and market-based methods required by the GHG Protocol Scope 2 Guidance, using a supplier-specific factor where you have one or a DEFRA 2026 default where you don’t.
Dual reporting. Purchased steam and hot water are Scope 2 energy, and the GHG Protocol Scope 2 Guidance requires two parallel figures: a location-based number using a grid- or region-average heat factor, and a market-based number using the factor that reflects the energy you contractually purchased. Both are reported.
Location-based = heat consumed (kWh) × average district-heat EF
Market-based = heat consumed (kWh) × supplier-specific EF
Supplier EF (efficiency method) = fuel EF ÷ generation efficiency
The efficiency method. Where a supplier discloses the fuel and conversion efficiency of the plant that produced your steam, the emission factor per unit of delivered heat is the fuel’s emission factor divided by the plant’s thermal efficiency — a boiler running at 80% efficiency emits more per kWh delivered than the fuel factor alone implies, because a fifth of the fuel’s energy never reaches you as heat. This is the supplier-specific factor that drives the market-based figure.
Where no supplier factor exists. If the supplier provides no disclosure, the market-based method falls back to the same average factor as the location-based method. The two numbers converge, and the absence of a supplier factor is itself a reportable data-quality limitation under the Scope 2 Guidance.
Reference: GHG Protocol Scope 2 Guidance (location/market dual reporting + the Scope 2 quality criteria) · GHG Protocol Corporate Accounting and Reporting Standard · DEFRA 2026 UK Government GHG Conversion Factors (district-heat and fuel factors).
Multi-site mode aggregates per-meter steam and hot water into a portfolio total with a per-site breakdown.
Applies to all sites uniformly.
Annualised: result × (12 ÷ period months).
Audit mode exposes the per-site, per-method calculation chain.
Enter purchased steam or hot water above to calculate
Location-based always shown. Market-based appears alongside when you supply your boiler fuel + efficiency or a contractual factor. Steam mass converts via saturated-steam enthalpy; a Scope 3 Cat 3 companion and a confidence rating are computed automatically.
Results are estimates based on the GHG Protocol Scope 2 Guidance and the EPA purchased-steam method. Steam mass is converted to delivered energy using saturated-steam enthalpy (ASME steam tables) net of the condensate/make-up return; hot water uses mass × specific heat × the supply-minus-return temperature difference. The supplier-fuel method recovers fuel input from delivered energy and the boiler/generation efficiency (EPA default 80%, gross-CV basis) and applies the boiler-fuel combustion factor. UK published factors are DEFRA 2026; other European countries use a EUROSTAT renewable-share-derived factor against a natural-gas-dominated fossil baseline (0.215 kg CO₂e/kWh) — refine with your network’s actual fuel mix or a supplier-specific factor where known. On-site combustion (Scope 1) and fuel well-to-tank / distribution losses (reported separately as Scope 3 Cat 3) are excluded from the Scope 2 figure. Full methodology notes.
Most companies meter the steam that arrives at their site and stop there. But the carbon in a kilowatt-hour of purchased steam depends entirely on what burned to make it and how much was lost in the boiler and the pipes — numbers that live with the supplier, not the meter.
Purchased heat is a Scope 2 line with two correct answers, and reporting only one of them is an incomplete inventory.
Purchased steam and hot water are Scope 2 and require both a location-based figure (average heat factor) and a market-based figure (supplier-specific factor). The supplier factor is the fuel emission factor divided by the plant’s generation efficiency.
Why purchased steam and hot water are Scope 2
The GHG Protocol Corporate Standard defines Scope 2 as indirect emissions from purchased energy — electricity, steam, heating, and cooling that your organisation buys and consumes but does not generate on site. Purchased steam and hot water sit squarely in this category. The combustion happened at the supplier’s plant, so the direct emissions are the supplier’s Scope 1; what reaches you is the delivered energy, and the emissions embodied in it are your Scope 2.
This is the same logic that places purchased electricity in Scope 2. The distinction that trips reporters is that steam and hot water are far less standardised than grid electricity. There is no single national steam factor the way there is a grid electricity emission factor. Each district-heat network or industrial steam supplier burns a different fuel mix at a different efficiency, so the carbon intensity of a delivered kWh varies widely between suppliers and must be sourced from the supplier wherever possible.
If you burn gas in your own boiler, that’s Scope 1. If you buy steam that someone else made in their boiler, that’s Scope 2 — the same energy, but the combustion sits on their books, not yours. You report the carbon that came with the steam; they report the carbon that came out of the stack.
Location-based and market-based: both are required
The GHG Protocol Scope 2 Guidance requires every Scope 2 energy stream to be reported two ways. The two methods answer different questions, and a complete inventory carries both.
Location-based
Uses an average emission factor for the heat network or region you draw from — the grid-equivalent for steam. It answers: what is the carbon intensity of the heat physically available in this location? It does not credit any contractual choice you have made about your supply.
Market-based
Uses the factor that reflects the energy you contractually purchased — a supplier-specific factor where one exists. It answers: what is the carbon intensity of the heat you specifically chose to buy? This is where a low-carbon supplier or a waste-heat network shows up in your numbers.
Reporting only the location-based figure hides the effect of a deliberately low-carbon supply choice; reporting only the market-based figure can flatter an inventory by leaning on contractual instruments without showing the physical reality of the network. The dual requirement exists so that neither distortion goes unchecked. For the underlying contrast, see the location-based vs market-based comparison.
The most common Scope 2 error is reporting a single steam number. The Scope 2 Guidance does not treat location and market as alternatives to choose between — both are mandatory disclosures for any reporter with purchased heat. A single figure is an incomplete Scope 2 inventory regardless of which method produced it.
The efficiency method for a supplier factor
When a supplier discloses the fuel and the conversion efficiency of the plant that produced your steam, you can derive a supplier-specific emission factor per unit of delivered heat. The factor is the fuel’s emission factor divided by the plant’s thermal efficiency:
The division matters because not all of the fuel’s energy reaches you. A gas boiler running at 80% thermal efficiency loses a fifth of the fuel’s energy as flue and radiative losses, so each kWh of heat that arrives at your site carries the emissions of roughly 1.25 kWh of fuel input. Dividing the fuel factor by 0.80 raises the delivered-heat factor by exactly that proportion. Ignore the efficiency and you systematically understate the carbon intensity of every kWh of purchased heat.
Think of efficiency as a tax on the energy in transit. If the boiler only delivers 80 units of heat for every 100 units of fuel it burns, then the carbon from all 100 units has to be spread across the 80 that reached you. That makes each delivered unit dirtier than the raw fuel number suggests — which is why you divide rather than multiply.
For combined heat and power plants the allocation is more involved, because the fuel’s emissions are split between the electricity and the heat outputs. That allocation is handled separately — see the CHP / cogeneration calculator for the efficiency-method split across both products. This calculator handles the heat-only case and the simple delivered-heat factor.
Which factor applies to you
The factor you use for the market-based figure depends on what your supplier discloses. The calculator selects the path from your inputs.
Supplier discloses a factor
Use the supplier’s published delivered-heat emission factor directly for the market-based figure. This is the highest-quality input and the one the Scope 2 Guidance prefers. Keep the supplier’s disclosure on file for assurance.
Supplier discloses fuel + efficiency
Derive the factor with the efficiency method: fuel EF divided by generation efficiency. The calculator computes this from the fuel factor and the efficiency you enter, so a supplier who tells you “gas boiler, 82% efficient” is enough to produce a defensible market-based number.
No supplier disclosure
Fall back to the DEFRA 2026 district-heat average factor for both figures. The market-based number then equals the location-based number, and the missing supplier factor is reported as a data-quality limitation. UK reporters use the DEFRA district-heat row; this resolves live in the calculator.
Best case, the supplier hands you a finished number. Middle case, they give you the two ingredients and you do one division. Worst case, they give you nothing and you use the regional default for both columns — which is allowed, but you have to say so. The quality of your Scope 2 number is set by how much your supplier is willing to tell you.
Worked example — gas-fired steam, supplier discloses fuel and efficiency
A UK site consumes 2,000,000 kWh of purchased steam in the reporting year. The supplier discloses that the steam is produced in a gas boiler running at 80% thermal efficiency but publishes no finished emission factor, so the market-based figure is derived with the efficiency method. DEFRA 2026 natural-gas and district-heat factors resolve live in the calculator; the gas factor used below is the DEFRA 2026 value.
| Step | Calculation | Result |
|---|---|---|
| Supplier delivered-heat EF | 0.18231 ÷ 0.80 | 0.22789 kg CO₂e/kWh |
| Market-based emissions | 2,000,000 × 0.22789 | 455,775 kg CO₂e |
| Location-based emissions | 2,000,000 × DEFRA district-heat EF | resolves live |
The market-based figure is 455.8 tCO₂e, derived from the gas factor (0.18231 kg CO₂e/kWh, DEFRA 2026) divided by the 80% boiler efficiency to give a delivered-heat factor of 0.22789. The location-based figure uses the DEFRA district-heat average factor, which resolves live in the calculator. Both are reported. A reporter who applied the raw gas factor without the efficiency adjustment would understate the market-based figure by 20%.
The efficiency adjustment is the whole point of the example. The raw gas factor (0.18231) applied to 2,000,000 kWh gives 364.6 tCO₂e — but that treats the delivered steam as if no energy were lost in the boiler. The 80% efficiency raises the true delivered-heat intensity to 0.22789 and the emissions to 455.8 tCO₂e. The 91-tonne gap is the boiler loss, and it belongs in your inventory.
Common purchased-heat reporting mistakes
The five errors that most often surface in assurance review of purchased steam and hot water reporting.
Disclosing a single steam number instead of both location-based and market-based. The Scope 2 Guidance requires both for every purchased-energy stream. A single figure is an incomplete Scope 2 inventory.
Using the supplier’s fuel emission factor directly as the delivered-heat factor, skipping the division by generation efficiency. This understates the delivered-heat intensity by the full boiler and network loss — typically 15–25%.
Booking the combustion emissions of purchased steam into Scope 1 because “it’s burning fuel.’’ The combustion is the supplier’s Scope 1, not yours. What you report is the Scope 2 energy delivered to your site.
Reading a network’s renewable-share percentage as licence to report the heat at zero carbon. A renewable share reduces the factor proportionally; it does not zero it, and the non-renewable remainder still carries emissions that must be reported.
Falling back to the regional default for the market-based figure without disclosing that no supplier-specific factor was available. The fallback is permitted, but the Scope 2 Guidance requires the data-quality limitation to be stated.
How this fits your wider Scope 2 inventory
Purchased steam and hot water is one stream in a complete Scope 2 inventory. Most reporters also buy grid electricity, and many draw on district heating or cooling networks that follow the same dual-reporting logic.
For purchased electricity — the largest Scope 2 line for most organisations — the Scope 2 electricity calculator applies the same location-based and market-based split using grid factors. If your heat comes through a district network rather than a dedicated steam supply, the district heating and cooling calculator handles the network-level factors and renewable-share treatment. Where your supply is backed by purchased energy attributes, the renewable procurement calculator handles the contractual-instrument accounting that feeds the market-based figure. Once the full Scope 2 picture is assembled, the SBTi near-term target calculator turns it into a validated reduction trajectory.
Frequently asked questions
Scope 2. The combustion that produced the steam happened at the supplier’s plant, so the direct emissions are the supplier’s Scope 1. What you buy and consume is delivered energy, and its embodied emissions are your Scope 2 — the same treatment as purchased electricity. Only steam you generate in your own boiler is Scope 1.
The GHG Protocol Scope 2 Guidance requires both a location-based figure (average heat factor for your region or network) and a market-based figure (the factor reflecting the energy you contractually purchased). They answer different questions and a complete inventory carries both. Reporting only one is incomplete.
Because not all of the fuel’s energy reaches you as heat. A boiler at 80% efficiency delivers 80 kWh of heat for every 100 kWh of fuel burned, so the emissions of the full 100 kWh are carried by the 80 kWh delivered. Dividing the fuel factor by 0.80 spreads the carbon across the smaller delivered quantity, raising the per-kWh intensity. Multiplying would wrongly reduce it.
Fall back to the regional district-heat average factor — for UK reporters, the DEFRA 2026 district-heat row — for both the location-based and market-based figures. The two numbers then converge. The absence of a supplier-specific factor is itself a reportable data-quality limitation under the Scope 2 Guidance, so disclose it rather than presenting the default as a supplier-verified figure.
A CHP plant produces both electricity and heat from the same fuel, so the fuel’s emissions must be allocated between the two outputs before you can derive a delivered-heat factor. That allocation is handled separately — see the CHP / cogeneration calculator. This calculator covers heat-only supply and the simple delivered-heat factor.
No. A network’s renewable share reduces the emission factor in proportion to the renewable and waste-heat fraction, but the non-renewable remainder still carries emissions. A network that is 70% renewable still has a 30% fossil component that must be reported. Treat the renewable share as a factor reduction, not a zero.