Getting Started

A Beginner’s Household Energy Audit

Jim Lambert

The background idea

• Set priorities to minimise our household energy use (greenhouse emissions)– Would need multiple actions– Needs some kind of analysis to decide

where to start

Household Setup• 1950s family home• Renovated 25 years ago• Good northerly aspect & some reasonable

passive solar design• 2 people (newly retired)• Electric off peak hot water• Gas space heating• No air conditioning• 1 car (old and thirsty)

Equipment (for collecting data)

• Normal electricity and gas meters

• Past records of gas and electric bills

Greenhouse gas estimates (past bills) Household energy component

Annual Greenhouse contribution (kg)

Relative greenhouse contribution (%)

Basic electric

(refrigeration, cooking, clothes washer, dish washer, lighting, computer, TV, chargers etc)

6,773 kg 37%

Off peak electric(hot water)

3,632 kg 20%

Space heating (family room)

2,660 kg 15%

Car (estimate over 8 weeks)

5,131 kg 28%

Total 18,196 kg 100%

Greenhouse Gas estimates

Basic electric (refrigeration, cooking, lighting etc.)Off peak electric (hot water)

Space heating (family room)

Car (estimated over 8 weeks)

Electrical Energy Usage (kWhrs) (from past bills)

0500

1000150020002500

normaloff peak

Electricity usage(Converting kWhr to its Greenhouse

equivalent)• Average (excluding abnormal periods)

5268 kWhr/year (603W continuous)

• greenhouse gas 6,479 kg/year (factor of 1.23 kg/kWhr from Univ of Sydney stinkOmeter on web)

Gas usage (MJ) (from past bills)

0

2000

4000

6000

8000

10000

12000

14000

season

MJ

usage MJ

• Average 38,000 MJ/year

• gives greenhouse gas 2,660 kg/year (factor 0.07 kg/MJ from stinkOmeter))

• Peak (for heating design) 207MJ/day in winter June-August

Gas usage(Converting MJ to its Greenhouse

equivalent)

Car – greenhouse emissions(Fuel consumed & Distance over 8 weeks)

• Average distance 286 km/week • Average consumption 15.0 litre/100km• 2.3kg greenhouse per litre of petrol

(source Australian Greenhouse Office Fuel Consumption Guide 2002-3)

• Fuel usage 15.0*286/100 = 42.9 litre/week• this would give greenhouse gas

2.3 * 42.9 * 52 kg/year = 5,131 kg/yr

Ideas from first pass• Spare refrigerator gone from garage• Solar hot water - easy and cost effective• Other electric has no quick fix

– Reduction in load is probably more attractive than 100% solar electric

• Replace car (60% less petrol consumption)

• Shade sails and skylight modifications for summer cooling

• Explore space heating and cooling (ground source heat pumps??)

Limitations of (electric) audit method

• Poor resolution of electric meters (1 kWhr minimum step)

• Difficult to separate multiple loads• Very indirect method

– not easy to focus on any particular device (e.g. refrigerator efficiency)

– Needs rather obsessive behaviour (difficult for loved ones)

• Separate portable meter availability??

Example of poor resolution “Background” (overnight) electrical consumption

Elapsed time (hr) 7.92 11.5 7.0

kWhr 2 3 3

Rate (kW) 0.253 0.261 0.429

Standby appliances unplugged

Standby appliances connected

Powermate meter from ATA

• David Hornsby (phone 9631 5413 direct)

• kWhr resolution 0.1 or 0.01

• Piggy-back plug

• Available for loan - 1 week $60

• Purchase price ~$300 for ATA members

Initial cost-benefit rankingalternative

actioncapital

cost $Annual

Greenhouse reduction (kg)

cost $/kg annual

solar hot water $2,000 3,632 0.6

replace old fridge with bar fridge $700 562 1.2

solar electric $25,000 6,773 3.7

solar space heating $10,000 2,660 3.8

new car $37,700 2,778 13.6