Personally I'm thinking rather than double your money THREE times would be better
So we hook a regular DC powersuppy up to the regular mains and feed it in to the solar panel DC wiring, simples
OK so you'd be paying around 10p-13p per regular kwh unit the PSU would use but then you'd be making around 30p per kwh on the other side
.......now that is a return ..........hypothetical of course
I have wondered whether there is anything to stop people doing this with the risk of bringing solar energy into disrepute when the lid blows off the scam. I have had a system installed and I asked the electricity company about this. The electricity company has technical details of your installation from the certificate provided by the approved installer (you have to use one of these to benefit from the scheme) and also has solar radiation records from weather stations, and if you seem to be generating a suspiciously large amount of electricity the company will come and investigate. If you make any modification to the system you have to tell the electricity company about it.
Under the scheme you have an additional meter that measures what you generate, and your normal meter that measures everything you take from the mains. The normal meter does not run backwards but freezes whenever power is flowing back through it. This means there is no measurement of how much you feed into the grid, and when the system is generating and you are using less than the generated power the actual amount you are using makes no difference at all to the reading of either of the meters. You are "deemed" to be feeding into the grid half of what is shown on the generation meter; my supplier E.On pays 3p per KWH for this. The 41-odd pence is for every KWH shown on the generation meter, regardless of whether it is fed into the grid or used on the premises. It is in addition to anything the supplier pays for the fed-back power. Schemes over 30KW get an "export meter" that does show the actual amount fed into the grid. I think it is possible to have a voluntary export meter on smaller schemes; I am trying to find out about this because I would like to have one.
I recommend this scheme if you have some money to invest and somewhere to put the solar panels. With the subsidy it probably pays more than you can currently get as interest on a savings account. It is even possible that it might pay enough to justify borrowing the money to pay for it in the first place; I should know more once my system has been up for a few months. If it does as well as the small solar panels I have had on the roof for the last few years for charging my electric motorcycle, then it will be a good investment.