Survey focus: the load nobody notices
Ākonga quantify standby and efficiency losses in real appliances and work out where the biggest achievable saving actually sits.
- Applied Survey move: Measured or sourced load audit
- Evidence it produces: A ranked saving list with the numbers behind the ranking
Lesson at a Glance | He Tirohanga Whakamua
Ngā Whāinga Ako | Learning Intentions
Students will know
- That standby power (vampire draw) is the electricity consumed by devices when they appear off or idle — and that most estimates put it at 5–10% of residential electricity use.
- How to calculate annual energy waste: standby watts × 8,760 hours ÷ 1,000 = kWh per year, then convert to cost (NZ rate ≈ $0.30/kWh) and CO₂ (NZ grid ≈ 0.1 kg CO₂/kWh).
- Why standby power exists: remote-control readiness, network connectivity maintenance, clock display, digital rights management — each is a designer choice, not a physical necessity.
- That energy labelling systems (MEPS, Energy Star, NZ star ratings) regulate active-mode efficiency but often undercount or exclude standby power consumption.
Students will demonstrate
- By completing a household standby audit: calculating annual kWh waste, annual cost in NZ dollars, and annual kg CO₂ for a standard device inventory.
- By redesigning one product feature to eliminate standby power waste — naming the specific feature, how it would work differently, and the one trade-off the change creates.
- By writing Design Journal Entry 15: a 3–4 sentence argument about whether standby power is a design oversight or a design choice — and what follows if it is the latter.
Do Now | Tīmatanga Whakaaro (7 min)
Display on the board — 2 minutes individual, 5 minutes class discussion:
"When you turn off your TV with the remote, how much electricity is it using? What about your gaming console, your phone charger, your microwave?"
Students almost always underestimate this. The television in standby mode uses 0.5–2W — the gaming console uses 0.5–15W depending on mode. The microwave clock uses 2–4W continuously. A phone charger with no phone plugged in draws 0.1–0.5W. None of this seems large individually, but multiplied across 10–15 devices in an average home, 24 hours a day, it adds up to a significant waste. Hold the calculation for the main activity — the Do Now is just about surfacing the hidden energy relationship.
Teacher note: The strongest opener is to bring a smart plug with energy monitoring (available for $15–25 at most NZ hardware stores) and measure actual devices in class. If that isn't possible, list the numbers on the board from the data table in the main lesson — seeing "my TV costs $8.76/year while doing nothing" is more memorable than any explanation.
Standby Power Data | Ngā Tatau Hiko (12 min)
Standby power is sometimes called "vampire draw" — it sucks energy even when the device appears off. The amounts are small per device, but the scale across millions of homes makes it significant. The key teaching point is not that standby power is large — it is that it is a design choice.
Note on NZ grid: At NZ's current grid carbon intensity (~0.1 kg CO₂/kWh, mostly hydro), the CO₂ cost of standby is relatively low compared to countries running coal-heavy grids. But the dollar cost is real, and the principle — why design in unnecessary consumption? — applies regardless of grid mix. As NZ phases out gas peakers, standby demand reduction also reduces peak-load requirements.
The design question: A Sky decoder uses 15 W in standby to maintain its Electronic Programme Guide and record scheduled programmes. A smart TV with streaming apps can do the same job using 1 W in standby. The difference is a design choice by the manufacturer — driven by cost (it's cheaper to leave the processor running than design a smarter wake-up system), regulatory inertia, and the fact that consumers almost never see the standby number on the packaging.
Activity: Household Standby Audit | Āta Arotake Kāinga (15 min)
Calculate Your Home's Vampire Draw
Use the data table above and the formula below. Work individually — the exercise is more powerful when students use devices from their own homes rather than a shared example.
Annual kWh = Standby watts × 8,760 hours ÷ 1,000
Annual cost = Annual kWh × $0.30
Annual CO₂ = Annual kWh × 0.1 kg
Step 1: List 6–8 devices in your home that are never fully switched off at the wall. For each, estimate the standby wattage (use the table or your own knowledge).
Step 2: Calculate the annual kWh, cost, and CO₂ for each device. Total them.
Step 3: Identify the single device with the highest annual waste. What would you need to change — in the device, in your behaviour, or in the product's design — to eliminate that waste?
Comparing your result: Published estimates for household standby waste generally land somewhere between $100 and $200 a year, but the figure moves with how many devices a home has and what electricity costs. Rather than take a number on trust, compare your class's calculated totals with each other. Whose household is highest, and what is driving it? Then have students check EECA's current residential energy data themselves and see whether their own arithmetic lands in the same range. Finding out that a widely-quoted figure is a range, not a fact, is part of the lesson.
Energy Labelling | Ngā Tohu Hiko (8 min)
NZ appliances are subject to Minimum Energy Performance Standards (MEPS) set by MBIE. Most also carry the NZ Energy Star rating (1–6 stars, with 6 being most efficient). These ratings primarily measure active-mode efficiency — what the device uses while you are using it. Standby power is often excluded, underweighted, or separately reported in fine print.
- Active power consumption per unit of output (litres cooled, lumens produced, etc.)
- Efficiency compared to other products in the same category
- Comparison across the product's expected useful life
- Standby power (often noted separately, rarely summarised)
- Embodied carbon (manufacturing energy not included in rating)
- Durability (a 6-star appliance that lasts 3 years vs a 4-star that lasts 10 years)
- End-of-life recyclability
Discussion: The NZ Energy Star rating is a useful tool for comparing products at the point of purchase. But applying our LCA lens: at which life-cycle stages does it provide accurate information, and at which stages does it tell us nothing? What would a genuinely complete rating system look like?
Activity: Smart Redesign Sprint | Hoahoatanga Hihiri (12 min)
Eliminate One Device's Vampire Draw
Choose the highest-waste device from your household audit — or one from the class data table. Your task: redesign ONE specific feature of that device to eliminate or dramatically reduce its standby power draw. The redesign must be:
- Specific: name the exact feature being changed (the always-on Ethernet port, the clock display, the IR receiver circuit, the network keep-alive process)
- Feasible: achievable with current technology (not "make it use no power" — that violates physics)
- Honest about trade-offs: what does the user lose, even slightly, by this change?
Worked example — Sky decoder (15 W standby):
The main standby load is the EPG processor keeping the programme guide updated. Redesign: Implement a scheduled wake-up system — the decoder fully powers down except for a timer chip (0.01 W), wakes at 3am to refresh the EPG, then powers back down. Trade-off: If the decoder is unplugged at 3am or the internet is down, the EPG may be 24 hours out of date. The user has to live with a small amount of lag in programme information. Annual standby drops from ~131 kWh to ~1 kWh — a 99% reduction.
Share with the class (2 min): What device did you redesign? What was the estimated standby saving? What was the trade-off? Collect answers on the board — look for patterns in which trade-offs students find acceptable vs unacceptable. That line is where real product design lives.
📓 Design Journal — Entry 15: Design Choice or Design Oversight?
Write 3–4 sentences responding to this prompt:
"Standby power could be dramatically reduced by design. It usually isn't. Is this a design oversight — an unintentional failure — or a design choice? If it is a choice, who is responsible for it: the designer, the manufacturer, the retailer, the regulator, or the consumer?"
Your entry should take a clear position on whether standby power is oversight or choice, name one piece of evidence from today's lesson that supports your position, and name one actor who could most directly change the situation.
Exit Claim | Whakamutunga (4 min)
On a slip of paper (anonymous, collected at the door):
"One design decision that creates standby waste is ______. One design decision that eliminates it is ______."
Teacher use: Look for specificity — "an always-on IR receiver circuit" rather than just "bad design." Students who can name the specific feature have understood the lesson. Students who give general answers ("inefficient components") have understood the concept but not the mechanism. Use the second lesson's opening to bridge from mechanism to design responsibility.
Kaiako Planning | Ngā Tūāhu Whakaaro
📋 Curriculum Alignment
This lesson addresses the NZ Curriculum Technology strand: Technological Knowledge — Technological Systems. Students examine how energy flows through technological systems and how design decisions at the component level have system-level consequences. The standby power calculation activity develops Mathematics competencies: proportional reasoning and unit conversion in a real context.
Science connections: Physical World (electrical energy, power, efficiency). The lesson deepens the LCA use-phase analysis from Lesson 11 — where Lesson 11 introduced the concept that use-phase energy varies by product, this lesson makes it quantitative and design-actionable.
📦 Materials & Resources
- If available: smart plug with energy monitoring (e.g. TP-Link Kasa EP25, ~$20 at Mitre 10 or PB Tech). Measuring a real device in class is far more engaging than using published figures.
- Calculators or devices for the household audit calculation
- Printed or projected data table of standby wattages
- Paper slips for exit claims
EECA resource: The Energy Efficiency and Conservation Authority (eeca.govt.nz) publishes NZ-specific residential energy use data including standby estimates. Their "Energywise" consumer advice pages are appropriate for student reading.
Teacher-sourced video suggestion: Search YouTube for "standby power vampire drain" or "phantom power electricity waste" — aim for 5–8 min, published by a utility company, government energy agency, or reputable science channel. A video that includes a power meter measurement is most engaging.
🔄 Differentiation
For students who need more support: Provide a pre-filled audit sheet with 4 devices already listed with their standby wattages — students only need to complete the formula. Provide the formula with units explicitly labelled at each step. For the redesign sprint, provide a worked example (not the Sky decoder one in the main lesson, so they have a fresh example to respond to).
For students who move faster: Research the IEA's "1-Watt Plan" — a global initiative from the early 2000s that aimed to reduce standby power in all devices to under 1 W. How far did it get? What happened to devices that exceeded 1 W? Why did the standard prove harder to achieve than expected?
For students with engineering interests: The technical mechanism for standby power is interesting: devices need to maintain a powered circuit to "listen" for remote control signals (IR or RF). The IR receiver in a TV draws 0.05–0.1 W continuously. Ask students to sketch a circuit design that could reduce this — a motion-detector trigger that only activates the IR circuit when the remote is in the room, for example.
⏭️ Next Lesson Connection
Lesson 16 (Smart Cities: Micro-Mobility and Sustainable Transport) scales the design thinking from the device level to the city level. The same question — why do systems consume more energy than necessary? — applies to transport networks. Students will bring the energy-audit mindset from this lesson to a much larger system. They should bring their Design Journal entries: the responsibility question (designer / manufacturer / regulator / consumer) is even more complex at the city scale.