How much resilience do you actually need?
The golden rule is proportion. Gold-plating a low-stakes fleet wastes money; skimping on an essential one is a false economy. Here's how to judge.
Last updated 15 August 2026
The most important resilience decision isn’t which battery or generator to buy — it’s how much resilience you genuinely need. Get that judgement right and the rest follows.
Start with tolerable downtime
Ask the blunt question: how long could the depot lose power before it seriously hurts the operation? A fleet with charged vehicles in the yard might shrug off a short overnight outage; an essential service might tolerate none. Your answer sets the level of resilience worth paying for.
Match the measure to the need
Resilience comes in tiers. For short interruptions, a battery sized with a little headroom, plus smart prioritisation, is often enough. For longer or critical situations, backup generation and islanding cover essential load — more capable, more expensive, and justified only where downtime is genuinely unacceptable.
Avoid both traps
Two mistakes cost money in opposite directions. Over-engineering resilience for a low-stakes fleet ties up capital in backup you’ll rarely use. Under-providing for an essential fleet is a false economy that shows up at the worst possible moment. The right answer is almost always somewhere in between, set by your honest exposure.
Design it in early
Whatever level you choose, build it into the design from the start — true islanding, battery backup roles and prioritisation logic can’t easily be bolted on later. Decide your tolerable downtime, buy the resilience that meets it, and no more. Proportion is the whole game, and it’s cheaper to plan than to regret.