Wattage & Efficiency Selection for A+
Short answer
At support level, choose a PSU by: (1) estimating the system's expected draw (based on CPU, GPU, drives, and peripherals), (2) selecting a PSU whose wattage rating exceeds that estimate by a sensible margin (commonly 20-30% headroom), and (3) preferring a unit with reasonable efficiency (80 PLUS rating) to reduce wasted energy and heat. Do not dwell on internal electrical design; focus on practical fit and thermal/energy implications.
Why it appears on the exam
- Given component power requirements, pick an appropriate PSU wattage with reasonable headroom. - Given two PSU options with similar wattage but different 80 PLUS ratings, pick the more efficient choice for a continuous-use workstation. - Identify when a PSU is undersized for a described system and recommend an appropriate wattage range.
Key concepts
Concept 1
Required terms
wattage rating: The maximum continuous power output a PSU can provide, expressed in watts. efficiency: The percentage of input power converted to usable DC output; the remainder is lost as heat. headroom: Extra wattage capacity above the system's expected maximum draw to avoid running the PSU near its limit.
Example
A basic office PC with integrated graphics and one drive might draw 150W; a 300-400W PSU provides safe headroom.
Concept 2
How Wattage & Efficiency Selection works
At support level, choose a PSU by: (1) estimating the system's expected draw (based on CPU, GPU, drives, and peripherals), (2) selecting a PSU whose wattage rating exceeds that estimate by a sensible margin (commonly 20-30% headroom), and (3) preferring a unit with reasonable efficiency (80 PLUS rating) to reduce wasted energy and heat. Do not dwell on internal electrical design; focus on practical fit and thermal/energy implications.
Example
A gaming workstation with a high-end GPU requiring significant power might need a 650-850W PSU depending on GPU TDP and other components; consult component power lists and add 20-30% margin.
Concept 3
Common confusion
- Relying solely on a large wattage label (e.g., 1000W) without checking efficiency or rail ratings; a high-wattage, low-efficiency PSU can be a poor choice. - Thinking wattage alone ensures compatibility; rail availability, connectors, and physical form factor also matter (connect to psutype2 and psubasic1).
Example
Choosing an 80 PLUS Bronze or higher PSU for a system that runs long hours reduces electricity cost and internal heat compared to a low-efficiency unit.
Concept 4
Core 1 (220-1201) question cues
Given component power requirements, pick an appropriate PSU wattage with reasonable headroom; Given two PSU options with similar wattage but different 80 PLUS ratings, pick the more efficient choice for a continuous-use workstation; Identify when a PSU is undersized for a described system and recommend an appropriate wattage range.
Example
A basic office PC with integrated graphics and one drive might draw 150W; a 300-400W PSU provides safe headroom.
Sample questions
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Q1.In an A+ question, this detail appears: A basic office PC with integrated graphics and one drive might draw 150W; a 300-400W PSU provides safe headroom. Which option matches it?
Q2.For this A+ objective, the scenario says: Choosing an 80 PLUS Bronze or higher PSU for a system that runs long hours reduces electricity cost and internal heat compared to a low-efficiency unit. What is the best match?
Q3.A user reports this support situation: A basic office PC with integrated graphics and one drive might draw 150W; a 300-400W PSU provides safe headroom. Which option should the technician choose?
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