Although household power prices have risen steadily over the last 20 years (and increased not so steadily in the last two!), PV feed-in tarifs have been falling

Although household power prices have risen steadily over the last 20 years (and increased not so steadily in the last two!), PV feed-in tarifs have been falling relentlessly (see slide 41 from https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/studies/Photovoltaics-Report.pdf https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p... for specific data) so as far as I can tell, the ROI period for household PV still seems to be measured in decades.