Friday, 16 January 2015

What did you get for Christmas?

One of the lowest electricity bills ever! At least the part of the bill that shows how much they pays us. December had all the wrong weather, and our earnings dipped under 30,000 yen for the first time. Six thousand yen less than the previous low in December 2012.

The first three years of our solar enterprise have been going well otherwise, and even this low monthly income was three times what we paid for the electricity we used.

In terms of energy use and generation is we're producing more than we're using, even in the lean months. 

So we could unplug from the mains and have more than enough energy for our needs. We're not in a hurry to do this, as it makes much more financial sense for us to sell all the electricity we produce in the day, and buy electricity at night. And at the moment we have no storage facilities, so we wouldn't really be able to. At some point I may calculate how big a battery we would need to keep enough electricity. The only useful data I have now is the number of days per year when we consume more electricity than we produce, which is under 50, or less than one day per week. Most of these days are between November and March. That data is not particularly useful: we don't need to store power for average situations, but for extreme situations, such as cold winter nights when our power source has been covered with snow for a couple of days, and it's dark anyway.

The amount of storage we need is a complex and exciting calculation, but for now we are connected to the electricity grid with cheap, night-time rates, and getting five times more for the electricity we sell in the day time for another seven years, so I'm not in a hurry to work out how big a battery we would need. 

Thanks for the card, Michael!