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Tuesday, 31 August 2010

How to save the planet (and my wallet) one electron at a time

My last quarterly electricity bill showed that the price of electricity had gone up by 10% fro 1 June, and the price hikes are expected to continue for many years. The $800+ quarterly bill showed that our daily household electricity consumption is around 48 kWh a day - which is much higher than the 'typical' household usage figure - so it is worth looking for areas where we can save power. I made up a list of all the electricity consuming devices in our home that I could think of, and used average hourly 'cost-to-run' figures and our estimated hours of use each day to calculate where our electricity was being consumed:


The grand total was surprisingly close to our actual bill, and it is immediately obvious what the most power-hungry devices are, and which devices get the most use. Some of these are definitely needs rather than wants (for example, turning off the fridge/freezer wouldn't be a smart move), and some of the power-hungry devices are used very little, so there isn't much scope for saving electricity. However, the stand-out items that are ripe for making significant savings are our computers (currently often left running all day and night) and the reverse cycle air-conditioning/heater.

Simply shutting down all our computers at night apparently could save around $50 a month! We could also save a significant amount by running the a/c intermittently, and wearing a jumper indoors, although that might be a tougher sell for DW and the kids. After those items it gets harder to find significant savings, but running the swimming pool filter for a shorter period (especially in winter when it's not being used), turning off the TVs when no-one is watching them during the evenings, and making sure lights are turned off in unoccupied rooms could save another $10 a month (although a cold, dark, silent house would be depressing). All up, we might be able to cut our power consumption by 20% with a few simple changes in our behaviour. Every little bit will help, as our supplier charges $0.1753 per kWh for the first 19 kWh/day, and the price rises to $0.255 per kWh for higher usage.

Another potential way to cut our power bill is to have a photovoltaic (PV) power generation system installed. A typical 1.5 kWh system (six panels) with an inverter costs around $13,000 installed, but, due to government rebates and credits, some providers have such systems advertised as 'from' $1900. However, the fine print adds in a couple of hundred dollars for 'extras' (such as installation on a tiled roof ($300), or a metal frame to install the panels at the correct angle on a flat metal roof, such as my garage ($300)), and for that price you also have to arrange and pay for the 'feed-in' smart meter to be installed by the electricity company (around $500). Our local government council also doesn't class PV systems as an 'exempt' development, so I'd have to put in a development application and have it approved (takes ~4 weeks) before signing a contract for the PV system. Fortunately the DA for a solar power system 'probably' won't cost anything according to the council planning department. So, all up, a 1.5 kWh system should cost me a bit under $3,000.

In Sydney the system should produce 5.85 kWh each day on average (the supplier quotes 7.3 kWh/day but I prefer to believe the official government 'green energy' website), which will earn $0.60 per kWh using a gross feed-in meter. That $3.85 a day adds up to around $1,400 each year, so the pay-back period should only be 2-3 years. The feed-in rate is fixed until the end of 2016 in NSW, so after the system has paid for itself we should 'make' about $1,400 a year for the following four years. After that the situation isn't so clear, as the feed-in tariff is likely to be cut to be closer to the usage cost. Once that happens the PV system output will cut our net electricity consumption by around 15%-20%, so there will be some ongoing benefit. The system has an expected life of 25+ years, although the PV cells lose around 0.5% efficiency each year.

I've also considered buying a 'heat-pump' water heater to replace our current 'off-peak' electric water heater (which is getting close to replacement age anyhow). However, even with the $600 government subsidy on heat-pumps, the new system would cost over $1,000. And apparently installing the 'smart meter' required for the PV system doesn't mean you automatically lose access to off-peak electricity (according to the electricity company rep), so it wouldn't be worthwhile having a heat-pump system (using electricity at $0.17 per kWh) replace the current off-peak system (using electricity at $0.076 per kWh). If it turns out that having the PV system installed does result in the removal of our off-peak electricity supply, I'll have to reconsider getting the heat-pump.

It will be interesting to see how well our energy saving efforts work out, and how convoluted, lengthy and expensive if turns out to be to have a PV system installed. I'll keep you posted on developments.

In a couple of years I'll be able to work out our actual savings - both in dollars and 'black balloons' of carbon dioxide emissions.

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