I have been contacted for a similar promotion.
Basically this company make profit by installing PVs on your property,
so they have free rent of space, and selling your solar energy to the grid.
You get pennies for the electricity generated and you cannot store it.
Then at night you paid full price for it.
After 20 years you might inherit the PV, which will be cheaper for the
leasing company to give them away to you than to have to remove them.
But also, after 20 years the PVs would need to be replaced anyway
with more performant ones.
This was a valid model in the past, but with the lowering cost of both
solar panels and batteries, if you can DIY this would certainly make more sense.