CCGT / HRSG Insulation Heat-Rate Calculator
Updated 11 June 2026 · ASTM C680 / ISO 12241 method
The only heat-rate-corrected insulation calculator for combined-cycle power plants. List your bare HRSG surfaces and see the gas or electricity recovered, CO₂ avoided and the heat-rate improvement (kJ/kWh) from Inzonex modular removable insulation — energy units only, apply your own gas/PPA price.
1 · List your bare HRSG surfaces
Laid out like a real HRSG — top deck and ground-floor deck, each carrying HP, MP/IP and LP lines (expansion joints, safety valves, valves, flanges and sensored flanges), plus a feed-water line. Laid out by HRSG line — HP (≈430 °C), IP/reheat (≈280 °C) and LP (≈150 °C), each with its expansion joints, safety valves, valves and flanges — plus a feed-water line. Edit area, °C and quantity to your plant. Fabric expansion joints carry more surface than their projected area — the public figure here is conservative (flat projected); the exact corrugation factor is applied in our detailed per-element study.
2 · Plant & fuel inputs
3 · Recovered energy & heat-rate
Get an exact quote for your HRSG
We'll reply with an exact quote and a PDF breakdown of your result (kW, MWh/yr, CO₂, payback). One email — no spam, unsubscribe anytime.
Heat loss from bare HRSG surfaces — by temperature
| Surface temp | Typical HRSG circuit | Bare loss | Insulated | Outer surface | Reduction |
|---|---|---|---|---|---|
| 150 °C | LP line / feed-water | 3,531 W/m² | 135 W/m² | 33 °C | 96.2% |
| 250 °C | IP mid section | 7,663 W/m² | 153 W/m² | 33 °C | 98.0% |
| 280 °C | IP / reheat line | 9,218 W/m² | 182 W/m² | 35 °C | 98.0% |
| 350 °C | HP / IP steam line | 13,575 W/m² | 259 W/m² | 38 °C | 98.1% |
| 430 °C | HP steam line / expansion joint | 20,079 W/m² | 361 W/m² | 42 °C | 98.2% |
How much can you save insulating hot expansion joints?
| Expansion joint (1.6 m²) | Heat saved | Energy / yr (8,000 h) | CO₂ / yr |
|---|---|---|---|
| at 150 °C (LP) | 5.4 kW | ~51 MWh-fuel | ~10 t |
| at 280 °C (IP) | 14.5 kW | ~136 MWh-fuel | ~27 t |
| at 430 °C (HP) | 31.5 kW | ~297 MWh-fuel | ~60 t |
Per-m² flux, ASTM C680 / ISO 12241, 50 mm Lamella (≤220 °C) or 100 mm Wired mat (>220 °C); gas displaced at 85% boiler-equivalent, IPCC NG factor. Your total = area × quantity — use the calculator above.
Method & assumptions — FAQ
Does insulating an HRSG improve the heat rate?
Yes — heat radiated from bare HRSG surfaces is energy the bottoming (steam) cycle would have recovered. Insulating returns it: less gas for the same MW, or more MWh sold. Recovery scales with ηbottom = (ηcc − ηGT)/(1 − ηGT). With η_GT 0.38 and η_cc 0.55 that is ≈0.27.
How is the saving computed?
Each surface: ASTM C680 / ISO 12241, convection (outdoor wind h = 5.7 + 3.8·V) plus radiation, bare (ε 0.95) versus 50 mm Lamella (Ts ≤ 220 °C) or 100 mm Wired mat (> 220 °C) with ε 0.9, outer temperature solved iteratively. Saved kW × hours → MWh-thermal; × η_bottom/η_cc = gas saved (fixed dispatch) or × η_bottom = extra electricity (power-limited). Never both.
What's the heat-rate improvement number?
ΔHeat-rate (kJ/kWh) = 3600 × annual fuel saved (MWh-fuel) ÷ net generation (MWh-e). It quantifies, in standard plant units, how much your specific fuel consumption drops once the bare surfaces are insulated.
Can expansion joints on a power plant be insulated?
Yes. HRSG fabric and metal expansion joints are usually left bare because they move with thermal expansion and must stay accessible for inspection — which is exactly what fixed insulation can't handle. Inzonex removable (modular) insulation is purpose-built for them: it accommodates the movement, is unzipped in minutes for inspection, and refits with no damage. So the joints that are normally the biggest bare hot surface on the plant can finally be covered.
How much does a bare HRSG expansion joint lose?
A typical ~1.6 m² fabric expansion joint loses about 5 kW at 150 °C, 14.5 kW at 280 °C and 31 kW at 430 °C — continuously, ~8,000 h/yr. Insulating one 280 °C joint saves ≈116 MWh-thermal and ≈27 t CO₂ per year; a 36-joint HRSG recovers ~500 kW (~990 t CO₂/yr).
What about cost and payback?
This public tool stays in energy units (MWh, CO₂, heat-rate). Per-element pricing and payback are confirmed after a short survey — use the quote button with your line items.