Compare two fictional proposals delivering the same 5000 kWh of useful electricity per year for 5 years. A (a local storage-backed system) has initial embodied emissions 10000 kg CO₂e and operating emissions 0.07 kg CO₂e per delivered kWh. B (a fuel-backed supply) has initial emissions 2000 kg CO₂e and operating emissions 0.4 kg CO₂e/kWh. The supplied rates include operating losses; ignore replacement and disposal only for this first calculation. Find total emissions over the stated horizon and the equal-emissions time. Then recommend how the decision should account for this constraint: qualified reliability requirements take priority over a carbon-only ranking. Do not assume these fictional factors describe actual products.

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Over 5 years: A 11750 kg CO₂e, B 12000 kg CO₂e. Equal-emissions time 4.8485 years. A has the lower modelled total; adoption also depends on the stated service and stakeholder constraints. Both proposals deliver the same useful service, so their operating emissions can be compared on a common boundary. Over 5 years the delivered energy is 5000 × 5 = 25000 kWh. Add initial and operating contributions. A gives 10000 + 25000 × 0.07 = 11750 kg CO₂e; B gives 2000 + 25000 × 0.4 = 12000 kg CO₂e. A starts with 8000 kg CO₂e more embodied emissions but saves 1650 kg CO₂e each year of operation. Dividing gives an equal-emissions time of 4.8485 years under the constant-rate assumptions. A carbon ranking is only one decision input: qualified reliability requirements take priority over a carbon-only ranking. Discuss who receives the benefits, who pays upfront, and whether either proposal reliably delivers the promised service before choosing. Make the recommendation conditional on verified service life, repair and replacement needs, disposal and representative operating factors. The stated calculation intentionally omits those effects, so it cannot establish the full life-cycle impact or guarantee that the ranking survives changed assumptions.

Reliable power at a service outpost

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