The calcs re solar are tricky, and the batteries are expensive. The long term price of energy is also difficult to predict. The situation we have at the moment in terms of high prices is man made and dependent on a specific set of circumstances, it's not due to any sort of fundamental lack of gas in the world. I don't think it will continue longer than a couple of years or so (but that of course is speculation). If I'm correct that means the prices could end up going down quite a bit in the near future, so predicting a ROI on solar is very difficult. I think it is also quite difficult to get a good price on solar installs atm, as a lot of the suppliers are loaded up with work.
These figures are really interesting, and suggest to me that our solar panels are actually saving us quite a lot, and that the payback time will be shorter than we originally thought.
We have a big old stone farmhouse with a 4 kw solar array on a south-facing roof, and our annual elec usage is about 2000 kwh. That's for lights, sockets, appliances, ovens, and occasional use of a plug-in oil-filled radiator in winter. My ballpark calculation is that solar provides roughly half our total elec usage. We don't have a battery with teh solar system, but we work from home so can run appliances during the day to make the most of the solar.
No mains gas here, but at current prices it costs the best part of £1000 to fill the oil tank (1000l) and we get through three of those a year. We've massively upped the loft insulation this summer, and having some of the most ropy windows replaced with double-glazed ones, so hopefully that will help keep the oil consumption down a bit.