Looking at how much electricity our solar array has generated prompted me to look at how much electricity we’ve been using over the last few years. I was able to dig out most of my energy bills back five years and used those in a similar process to graph our usage – see the chart above.
One of the first things that is obvious is that there is only data for the four quarterly bills in a year, there is no data per month never mind per week. This general point highlights how poor are the systems in place for tracking energy usage. I didn’t realise it before this exercise but our meters are only read about twice per year (typically in May and November) so there’s no real indication of how much energy you are using at any time, and the bills in between these readings are just based on estimates.
Of course the government has plans for everyone to get smart meters installed to give better tracking of energy usage. However, the start of the rollout was planned for next year and has just been delayed by a year. They won’t be fully in place before 2020 which is a long time to wait. In the meantime to address the issue of a lack of detailed information on energy usage I have started to manually record the electricity (and gas) meter readings once per week.
Anyway, back to the chart. Given the lack of data, and its questionable accuracy (since it includes estimated readings) it is dangerous to deduce too much from it. It fairly clearly and as expected shows higher electricity usage in winter months compared to the summer – presumably from more use of lighting, and perhaps more time spent indoors watching television, etc.
I would also like to conclude from it that our usage of electricity from the grid has reduced since installing solar, i.e. that the values for 2011 and 2012 are lower than previous years. However, that is not obvious, and in particular the usage for Jan/Feb 2011 is particularly high. It would probably be wishful thinking anyway, since we are often out (and hence electricity usage is low) when the sun is shining brightest. So what can be done to get more benefit from solar?
There are three key income elements to the government’s solar feed-in-tariff system:
- You get paid a generation amount for each unit of electricity generated.
- You get paid for each unit exported to the grid. However, since there are no smart meters in place yet this is done notionally: you get paid an export amount for exactly half of what you generate as though you exported it.
- Given that the export isn’t metered, you can use the electricity you generate for whatever you want for free.
This means that there is a clear economic benefit to using as much of the electricity you generate as it is being generated, since it deemed to be exported but is actually available to use. This ignores, of course, the complex moral question of whether you should just export it anyway so as to reduce your neighbours’ carbon footprints regardless of the economic cost to yourself, and I may return to this question in a future post.
Anyway, assuming for now the aim is to get the best economic benefit from the solar array, I have been considering some ideas on how to achieve it:
- We need to defer our electricity usage to the times when most electricity is being generated. This means, for example, operating the dishwasher and washing machine during the day rather than in the evening (and so using their timer functions if we are out during the day).
- Use some electricity storage such as batteries. However I believe such systems are still too expensive to be economically justifiable.
- Heating our water electrically to save on gas usage, i.e. operate our electrical immersion heater from solar during the day. There are some technically advanced systems for doing this such as Immersun but they are expensive and so payback would take a long time. I am currently looking into simply running the immersion heater from a timer during the summer months so it operates during daylight hours.
As well as economic benefits I am determined to reduce our family’s carbon footprint – getting the solar array and the ZOE are the key elements to this. There are also other approaches and lifestyle changes that I will be investigating; others are further along this road than I am and I recommend anyone interested to research further. I have put some starting links on the Links page, for example the excellent Earth Notes site.