A sunny day in Melbourne!

Why do we love sunshine?

Because we've got solar panels on our roof!

How much solar power do we have?

We've got a 2.4kW system - which is as big as our roof space would allow for, which means in full blazing sun we make 2.4kW. So an hour of sunshine makes 2.4kWh - in the middle of the day when all the panels are in full sun.

So how much energy (power) do we make?

On a day like today - a glorious blue sky summer day we typically generate a little over 14kWh.

Solar display panel for 8th January 2014

What do our power bills look like?

Quite simply they are more of a credit note than a bill!

Back in October we wrote about our average electricity usage - which is still about 4.5kWh (per day) so we feedback about 10kWh into the grid - which equates to $3.50 back into our pocket. Last month (our power company has recently switched to monthly billing) we made $43.54, bringing our total credit to $176 - which will more than cover lower power generation through the darker winter months.

The really nice thing is our solar system will have paid for itself in about three and half years from now. Which we think is $6,000 well spent!

Powered down

How much power does the "average" household use each day?

While it's hard to pin down a figure (a five person household would use a lot more than a single person household) most estimates are around 18 to 20 kWh. The Australian Energy Regulator has a handy little online tool that provides a more meaningful average household usage for your 'localised zone' (you provide your postcode) and number of people living in your home. 

For a two person household in Melbourne's east here's the averages:

Just what is a kWh?

Thankfully one of us has a degree in physics and can explain this one!

A kWh is 'kilowatt hour' - which is a unit of energy (not power). 

Energy is power multiplied by time, so the 'kW' is the power and the 'h' is the time (in hours). So if you have a 1 kW appliance running for 1 hour, then you've used 1 kWh.

As a point of reference:

• A typical electric kettle about 2 kW
• A split system air conditioner is between 3 and 9 kW 
• An electric oven around 1 kW

How does the typical household use their electricity?

About a third goes on heating and cooling - so good insulation and putting on a jumper when you get cold can make a huge difference. White goods have the next biggest impact - so think about what you need plugged in and running year round and buy the most efficient product you can afford, it will make a difference to each quarterly bill. Lighting while around 10 percent can easily be reduced by replacing old inefficient bulbs with compact fluorescents. Better yet replace them with LEDs - expensive just now, but prices are coming down and the range of options getting better every year.

What's our average electricity usage?

About 4.5kWh (per day) in winter; about one third the average use. Here's some of what we do to use less electricity:

• We have gas hot water
• Heating and cooling - our house is well insulated, so we use a lot less of both. Our heating is underfloor hydronic heating, so uses very little power. In terms of cooling we have invested in good quality outdoor blinds and inside we have thick curtains. Last summer we ran our air conditioner no more than half dozen days, and when we run it we have it set for 24 degrees.
• We make an effort to turn off lights when we leave the room. All of our lighting is compact fluorescent, which use less electricity. We are investigating the use of LED lighting which would reduce this further. 
• Other than the fridge we don't have any appliances on standby, even our wireless Internet is off at the mains when we're out.
• We've bought the most efficient appliances we could afford - washing machine, fridge etc.
• We try to run a full load in the dishwasher and washing machine - and we line dry the washing, no tumble dryer in this house.
• And finally a confession we don't own any of the following: TV, microwave, stereo, toaster or hair dryer - which also has an impact.

The Power of Gas

Why choose gas?

Gas is much more efficient for heating than electricity. For example an efficient gas heater is estimated to cost $159 a year to run. This compares with an electric radiant heater at $471 and an oil filled column heater costs $330 a year. There are also savings to the environment (and your household budget) when it comes to hot water systems. Gas hot water systems produce about a third of the greenhouse gas emissions of electric storage hot water systems.

Why should we aim to use less gas?

Gas is more efficient than electricity, but that doesn't mean we shouldn't aim to use less of it. Australia's households account for almost 20 per cent of our national greenhouse gas emissions. Choosing efficient appliances and making simple changes to the way energy is used means you can reduce your impact on the environment (which is what this blog is all about) and save money.

How much gas does the average Victorian household use?

Well the short answer is after a bit a research we’re not entirely sure. There's quite a lot of data on electricity usage (and more on that from us in a future blog) but very little on reticulated (mains) gas usage. We found this a little odd because according to Department of Environment and Primary Industries Victoria has the most extensive reticulated gas network in Australia, so why the lack of data on average usage? The closest we came to an estimate was 52,000MJ / year - and this was from a NSW electricity company.

How much gas have we used in the last 12 months?

Easy! We've done the calculations and know that we have used 13,582MJ, or around a quarter of the average Victorian annual household usage. To put this in perspective we have gas heating, hot water and a gas stove top.

What can every household do to use less gas?

• If you are buying a new gas appliance (or building) buy the most efficient appliance you can afford - it will pay for itself over time. Consider a solar hot water system with a gas booster. We were fortunate to purchase a home with gas hot water and a hydronic central heating system.
• Check your household insulation - more is better.
• Consider what is cold, can you put on a jumper and leaving the heating off? Broad estimates are that for every degree you decrease your heating setting you can save 10 percent of the running cost. 
• Avoid running heating when the house is empty, timers are great but use them to their best advantage, not just as a default for winter.
• Open curtains during the day - and close them at night. This allows for passive heating from the sun during the day and keeps the heat in at night. Curtain Pelmets, while ugly also make a big difference.
• Buy a door snake - draft excluders trap the warm air in and keep the cold air out.
• Assuming you have gas hot water, use cold water where possible.
• Reduce your water heater thermostat to 60 to 65 degrees Celsius. Do you even know what temperature your thermostat is set at?

Finally have a read of a post by Tom Murphy on how to slash domestic gas consumption by a factor of five - be warned it gets a little technical in places!