Photovoltaic cells

You mean a clamp metre… yes they exist. I have one in the garage somewhere.

https://www.test-meter.co.uk/ac-dc-clamp-meters/

Ah! I knew someone would know! However, what I was hoping for was something I could clamp around the supply wire for say a day/week or so and understand what the consumption was over that period. So rather than just confirming what the draw was when it was on which I assume is what a clamp meter would do, it would tell me what my usage of the item was over that period. Maybe clamp meter can do that?

All the ones I’ve seen are as hand held testers but I’ll be surprised if someone out there doesn’t make something similar to what you need.

Oh… btw. You need to clamp the live wire only on the mains cable. I’ve seen gadgets that you plug into a mains socket and they split the live and neutral so you can then use the clamp metre over the live.

I installed 14 panels on a South facing roof at the end of January. That amounts to a 4.2Kw capacity at full tilt. There are 4.8Kw batteries in the attic. The system first powers the house, then feeds the batteries. If batteries are full it then powers the immersion hot water heater. When that reaches its limit it returns any further surplus to the grid.
I’m in Ireland, where the installer is obliged to inform the Grid Utilty about a new ‘microgenerator’.
Hotfoot, (about a month later) the Grid boys arrived to replace my electromechanical meter with a new ‘smart meter’. Objective is that they could separate incoming from outgoing electricity, charging full whack for the former, while paying a pittance (if anything?) for the latter.
They had a look at the meter installation and concluded that it was a large job to replace, so took some photos to bring back to the office.
Haven’t seen them since. Meantime, many days the meter has gone backwards!
My objective was to reduce CO2 emissions rather than to save money, but I seem to be achieving both comfortably. My meter reading today is 89529 vs 88522 on Feb 1st. That’s about 6 units a day, compared to 29 units a day in 2017, although admittedly my son has moved out since, and I also made other changes which would have reduced electricity consumption.
I think this technology is wonderful and it gives a great sense of satisfaction to see it working. One difficulty is the need to retrain ‘her indoors’ to work to the rhythm of the sun, operating the the heavy users (Oven, Dryer, Washing Machine, Dishwasher) while the sun is shining strongly. The heaviest use is the ‘Self Cleaning’ oven.
Still, until the ‘Grid boys’ come back, I’m getting credit for everything, whether I use it or not!
Today we generated 20kw and consumed 14kw. Result, happiness!

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Have a look at the intuition OWL-PV app; it helps to show when one is exporting so is a good time to put the washing machine on.

I have an app called ShinePhone which shows me exactly what is going on all the time and accumulates daily statistics.

Have you carried out a cost benefit analysis? I know you say you’re doing it for environmental reasons but I’d be interested to know how it pans out financially over time

I reckon I’ll get my money back in about 8 or 9 years. Given that the opportunity cost is close to zero (bank interest rate), I’m happy with that, but for me the return is the reduction in CO2 and the satisfaction of not paying the utility company.

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We’ll pay our installation off within 7-8 years, and then it’ll be gravy all the way from there. But I reckon we actually save more by just being much more aware of electrical use, and using less.

So what’s the lifespan of these products and how long do they remain serviceable?

That remains to be seen. My expectation is that it will start to dip in performance close to the ‘cash recovery’ point, but that by then the technology will have advanced significantly, making the next round cheaper (without a subsidy) , always assuming The Planet survives!

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25 to 30 years. Of course, that is a projection based on accelerated life testing, it will be a couple of decades before we know for sure.

Regardless of the replacement cost of panels and invertors, there is quite a high cost to install the required amount of scaffolding so that the replacement / servicing of the panels can be done safely.
Our panels went live in November 2011, so we get the good FIT rate, however we paid a premium to get it installed before the rate changed.

The FIT payments have now paid for the initial install, plus the reduction in electricity use costs. However we spent quite a chunk of cash in 2016 to replace the invertor and to rewire the panels in parallel to improve power. So it will be a couple of years to be fully in profit (unless something breaks or needs work).

The whole project is a bit of a gamble of yield versus the number of years left to enjoy it.