What is The Gas Consumption of a 1,000 kW Boiler?

Estimate gas consumption for a 1,000 kW boiler with step-by-step calculations, typical efficiencies, and m³/h worked examples.

Key conversions and typical numbers

• Power → energy/hour: 1 kW = 3.6 MJ/h, so 1,000 kW = 1,000 × 3.6 = 3,600 MJ/h.
• Natural-gas calorific values vary by composition and reporting convention:
  • Typical lower heating value (LHV) ≈ 35.2 MJ/m³ (net heating value — water vapour not condensed). Use this for practical combustion/fuel calculations.
  • Typical gross/Higher Heating Value (HHV) can be ~38.9 MJ/m³ (depends on supplier/region). Metering and billing conventions differ — check your gas supplier.
• Typical modern natural-gas boiler efficiencies:
  • Non-condensing: ~80–88% (often ~85%).
  • Condensing: 92–95% (modern condensing units). Actual season/annual efficiency can be lower depending on system.

Formula (step-by-step)

1. Convert boiler output to MJ/h:
   Energy_out (MJ/h) = Power (kW) × 3.6
2. Fuel energy required (MJ/h) = Energy_out / Boiler_efficiency
3. Gas volume (m³/h) = Fuel energy required (MJ/h) / Gas_calorific_value (MJ/m³)

Or combined:

Gas (m³/h) = (Power_kW × 3.6) / (Efficiency × CV_MJ_per_m3)

(Where Efficiency is a decimal, e.g. 90% = 0.90.)

Worked examples (1000 kW boiler)

Using 1,000 kW → 3,600 MJ/h.

Calculated results (two representative calorific values and three efficiencies):

(Example numbers calculated from the formula above; inputs for CV come from typical gas tables — actual CV must be confirmed with your supplier.)

Quick takeaway: For a 1,000 kW boiler you’d expect roughly 100–120 m³/h of natural gas depending on boiler efficiency and the gas calorific value used for the calculation.

Practical notes & caveats

• Metering & billing: Gas suppliers often report volume at standard conditions (Nm³) and provide the exact calorific value you must use for energy/billing — always use the supplier’s CV for final calculations.
• LHV vs HHV: Use the same basis for CV and boiler efficiency. Most combustion/efficiency work uses LHV, while some technical tables quote HHV — mixing them causes errors.
• Seasonal/real efficiency: The boiler’s rated efficiency (e.g., 95%) is a lab/steady-state number; real annual efficiency may be lower due to cycling, standby losses, distribution losses, and low return temperatures.
• Gas composition matters: Methane content, inert gases, and Wobbe index change the CV. If you need accuracy for fuel purchase, emissions or cost modelling, get the supplier’s CV and use that.

Short checklist to estimate your site’s gas use accurately

1. Get the boiler’s measured/guaranteed efficiency (or use manufacturer data).
2. Ask your gas supplier for the actual calorific value (MJ/Nm³) for the relevant billing period.
3. Use the formula above and report results in m³/h or Nm³/h depending on your supplier’s units.
4. If you model cost, multiply m³ by the unit price (and include taxes/transport/standing charges).