I have now collected a year’s worth of data on how my modest, 1.68kW peak PV system has performed over the last twelve months, and it makes for interesting reading.
Over the period October 2011 through to the end of September 2012, I generated a total of 1075 kWhs. Across that same period I consumed a total of 2218 kWhs of electricity (a large jump upwards from years gone by and I’m at a bit of a loss to explain where that increase has occurred – but that’s for another blog post). So in total I have generated a little less than half my yearly demand.
My new backstop meter, installed at the end of September 2011, informs me that my total net electricity demand over the last 12 months, that is from the grid, totaled 1430 kWhs.
Hence that in turn that tells me that my PV system has fulfilled approx 35% of my total electricity use over that time period; not bad for a small system!
Even more encouragingly, it also shows that I have managed to locally utilise around 75% of my total PV generating capacity. Only 26.5% was exported out to the grid. We have been changing our habits and behaviours to maximise usage and also, as I work from home for a significant proportion of the day, I am able to take advantage of sunny afternoons to put the washing on, and to cook meals, but regardless I’m particularly proud of this statistic.
When we come to payback times, the data isn’t so encouraging. An approximate 1000 kWh annual output has garnered me around £450 in FiT payments this year, including the extra 3pence for 50% of the generating capacity that is assumed is put back into the grid (for me that is generous as I’m only putting back 25%!).
The 788 kWh of free PV electricity I have used has saved me around £100 in annual electricity charges.
Put together that adds up to a total of £550 savings per annum. On a £8000 original outlay, it will take around 15 years to pay back the original capital cost. Far greater than the sub 10 year claims that abound in the industry. This doesn’t overly concern me, as there is another 10 years of useful service out of the system after all original costs are paid off, and the point of having the system wasn’t just to get a quick payback. But it is an interesting finding, and I would very interested in hearing from other PV owners to see if I am typical or whether my smaller than average system, and the fact I do not have a perfectly due south aspect has reduced my generating capacity to a significant extent?
So, please get in touch if you have an interesting PV generation story to tell. is your system over- or under- performing? and if so, why do you think that is?
Other related blogposts on PV generation and ownership by paula owen consulting: