Energy efficiency upgrades for Perth homes: ranked by payback period

Perth households spend on average $1,800–$3,500/year on electricity. The highest-return energy efficiency upgrades reduce this spend permanently — without requiring solar panels. Here's a ranked list of common upgrades by typical payback period for Perth conditions.

Ranking methodology

Payback period = Upfront cost ÷ Annual savings

Perth-specific assumptions:

• Electricity tariff: A1 (33.26c/kWh) or Midday Saver peak (55.33c/kWh) where applicable
• Perth climate: hot summers (AC load), mild winters (low heating demand), 8-month warm season
• Household size: 3–4 person family home, 2,000–3,000m² lot, 4-bedroom home

1. LED lighting upgrade

Upfront cost: $5–$30 per globe replacement (DIY), or $500–$2,000 for whole-home LED downlight upgrade

Annual saving:

• A home with 20 halogen downlights (50W each) running 5 hours/day costs approximately $615/year (20 × 50W × 5h × 365 × 33.26c/kWh)
• 20 LED equivalents (7W each) costs approximately $86/year
• Annual saving: approximately $530/year

Payback: 1–4 years (depending on method — DIY globe swap vs full recessed LED replacement)

Perth note: Perth's AC is more impactful than lighting, but LED upgrades are the cheapest and fastest-payback first step.

2. Ceiling insulation (if absent or inadequate)

Upfront cost: $1,500–$4,000 for a typical Perth home (installed R4 or higher in ceiling)

Annual saving: Reducing air conditioning load is the primary saving in Perth. Adequate ceiling insulation (R3.5–R5 for Perth climate zone) can reduce summer cooling electricity consumption by 15–30%.

• Ducted reverse cycle (10kW) running 6 hours/day for 90 summer days at 3kW average draw: 90 × 6 × 3 × 33.26c = $540/summer
• 25% reduction from insulation: $135/summer saving
• Heating saving (winter): minor in Perth (mild winters, low heating demand)
• Annual saving: approximately $150–$300/year

Payback: 5–15 years (highly variable depending on existing insulation, house construction, AC use)

Perth note: Insulation is more impactful in hotter suburbs (Midland, Armadale, Kalamunda) than coastal areas. Homes with no ceiling insulation (pre-1970s) get faster payback than homes with partial or aged insulation.

3. Heat pump hot water system (replacing electric storage)

Upfront cost: $2,500–$5,000 installed (after STC rebate approximately $300–$700)

Annual saving: A 250L electric storage hot water system running off-peak costs approximately $400–$600/year. A heat pump on Midday Saver (8.85c/kWh) costs approximately $80–$150/year. Annual saving: $250–$500/year

Payback: 5–10 years (faster with gas elimination and supply charge saving)

Perth note: Strongest payback when replacing a gas hot water system and eliminating the gas connection (saving $200–$280/year in gas supply charge). Combined saving can be $450–$780/year.

4. Variable speed pool pump (replacing single-speed)

Upfront cost: $1,200–$2,500 installed

Annual saving: A single-speed pool pump (1kW) running 8 hours/day costs approximately $974/year (A1). A VS pump at low speed (0.25kW) for 8 hours/day costs approximately $243/year. Annual saving: approximately $730/year (including reduced backwash hours at higher speed)

Payback: 2–3 years

Perth note: Pools are common in Perth; a VS pump is consistently one of the fastest-payback upgrades available.

5. Air conditioner replacement (old inefficient unit)

Upfront cost: $1,200–$4,000 for a new split system (installed)

Annual saving: An old 3-star air conditioner (COP 2.5) vs a new 5-star unit (COP 4.5):

• Running 4 hours/day for 90 summer days
• Old: 1.8kW draw × 4h × 90 × 33.26c = $215
• New: 1kW draw × 4h × 90 × 33.26c = $120
• Annual saving: approximately $95/year per unit

Payback: 10–20 years for a single split system (varies widely by unit, usage pattern, and running hours)

Perth note: Replacing still-working AC is rarely the first priority — the payback is moderate. But if an AC unit is approaching end of life or is a very old unit with unknown COP, replacement is worth considering.

6. External window shading (awnings, external blinds)

Upfront cost: $300–$1,500 per window (external roller blinds, motorised awnings for west-facing windows)

Annual saving: West-facing windows in Perth receive intense afternoon sun (2pm–6pm). External blinds can reduce cooling load on a west-facing room by 20–40%.

• A room with west-facing windows running AC at 1kW for 4 hours on 60 summer afternoons: $80/summer
• 30% reduction: $24/summer per room
• Annual saving: approximately $30–$100/window per summer season

Payback: 10–25 years per window (slower individual payback, but comfort improvement is significant)

Perth note: External shading improves comfort significantly on hot Perth evenings. Financial payback is secondary to comfort.

7. Ceiling fans

Upfront cost: $150–$600 per room (installed)

Annual saving: A ceiling fan (20–75W) costs approximately $2–$7/month. Running a ceiling fan with AC set at 25–26°C (vs 22–23°C without) saves approximately 10% of AC electricity:

• At 1kW AC draw × 4h × 90 days × 10% saving: approximately $12/room/summer
• Annual saving: approximately $10–$20/room

Payback: 10–25 years per room for financial payback alone — comfort payback is immediate

Perth note: Ceiling fans are a comfort upgrade first. The financial saving is modest but the comfort improvement (distributing cooled air, enabling higher thermostat settings) is genuine.

Overall upgrade priority for Perth households

Fastest payback (under 5 years):

1. LED lighting (DIY globe replacement)
2. Variable speed pool pump (if you have a pool)

Medium payback (5–10 years): 3. Heat pump hot water (especially gas replacement) 4. Ceiling insulation (if currently absent)

Moderate payback (8–20 years, but strong non-financial benefits): 5. External window shading (comfort + energy) 6. Ceiling fans (comfort) 7. AC replacement at end of life

Solar (separate category): A 6.6kW solar system ($4,000–$6,500 installed) typically payback in 5–8 years and is often the single largest energy bill reducer for Perth households. It complements (rather than competes with) the efficiency upgrades above.

Your electricity bill shows where your money is going. Upload your Synergy bill to BillWise to identify your top electricity costs and model the savings from specific upgrades based on your actual consumption.