Thursday, 14 January 2010

Could we be Self-Sufficient in Electricity?


It is Summer in Australia so our photovoltaic panels should be producing near peak capacity. In fact, according to our last bill, we used 6.2 kWh per day and generated 6.4 kWh per day over a 93 day period (September 15 2009 to December 17 2009). So we are sort-of in the black this quarter.

Unfortunately, we still have to pay a service charge of 48c per day + GST. We need the grid to supply electricity when the sun doesn't shine and to provide a sink for our excess electricity during the day when it does.

We are cheating a bit: we don't have air-conditioning; we use Natural Gas for stove-top cooking and hot water heating; and we have a reasonably efficient wood heater for winter.

Our oven is electric. Other than that, we run a large fridge and freezer, water pump, ADSL router, 4 laptops, printer, microwave, 8kg front-loader, dishwasher, microwave oven, small TV, toaster, 2 garage door openers, range-hood, smoke detectors, alarm system and the usual interior and exterior lights. We have other appliances but they are used rarely.

Notably, we don't run a VCR, DVD player, stereo or electric kettle.

On the other hand, our house doesn't really need air-conditioning by design. We have double glazing, reasonable wall and ceiling insulation and full-brick downstairs sitting on a thick concrete slab that is in contact with the ground (ie. we don't have poly-styrene blocks under our slab).

Our gas bill varies seasonally. In summer we consume about 18MJ per day and in winter this roughly doubles. Most of our gas consumption is used to heat water for bathing. Our gas costs us $27 + GST for October-December but the service charge was $44 + GST!

It is unlikely that we will generate enough electricity to make-up for what we use, but we should come close.