Noted, it's some time ago, but not a long time back. I measured the viability of installing the PV array measuring the payback against spending the same money in NG stock. Using the dividends from NG to buy my energy. The NG stock won on the basis that it covered my energy bill and at the end of the useful life of the PV array (worth nothing), NG stock would still be worth having. Of all the companies out there, NG is one that is not going out of business anytime soon. ........Part of my professional responsibilities covers a 500 megawatt CCGT plant, so a couple of kw PV array will be easy!
I rather suspect that the practical lifetime of modern A or B grade solar PV will be more like 40-years. We used to figure on a new inverter every 5 years, and about 20-years for the panels. The inverters are often doing 10-years, and the degradation of modern solar is so little that I think we will in practice get 40-years with trivial maintenance. There are not many CCGT or OCGT plants that will see 40-years, even with intensive maintenance, and like you I know because I have done it.
May I gently suggest that the next 10-20-years of NG & DNO investment risk is going to be like nothing in the last 70-years (i.e. the 70-years since the UK etc grids were built out in earnest). In my own perfectly ordinary terraced house I am only £3k of expenditure away from the grid serving no purpose beyond a mere timing signal for 10-months of the year (and I think I can get that to 12-months, tbd). That statement ought to have every shareholder in NG, or DNOs, or generators quaking in their boots - and I know because of my connections that it is a risk recognised at board level by some (but not all) of the more farsighted boards.
The reason I say that is because my preferred solar installer is now able to do a basic LiPo battery system of 2.9kWh for £2000, with additional plug-in battery modules of 2.9kWh for £800/each. That's remarkably cheap, more typically they are still at the £10k price point. Already the only thing that actually costs me any money is the standing charge, and since I am ordinarily (time-wise) an exporter (and I am an overall net exporter) I think the DNO/NG should be paying me the standing charge. I am beginning to get seriously ticked off by being charged £85/year for standing charges when I am the supplier. If I were to put in a battery and stand my own interruption risk, I might just go on strike (i.e. go offgrid, cutting the gas connection as well). Now societally that would be a bad decision, but it gives you a feel for the way the wind is blowing. NG & DNO shareprices don't seem to reflect that risk sufficiently imho.