This has been a very ££££££bn's cost slow car crash to all power users & they are about as much use as a chocolate teapot. All suppliers used their own bespoke incompatible with each other systems, so 'have fun' if fitted and you change supplier!
This year they should finally be rolling out the mk 2 specification that is finally a common standard for all suppliers.
They can't currently force you to have one fitted but the energy suppliers can get a bit upperty over it, if you say no, as they have government 2020 installed base targets.
Anybody that has had one fitted says it is like getting a toy for Christmas and after the 10 minute novelty wears off playing with the packaging it came with was more interesting. In the boxing day tidy up it is slung in the back of a cupboard never to be touched again.
The two Ed's Ed Millipede and Ed Davey were behind this to keep the tree huggers happy. Ed Millipede was also the driver behind the Climate
Fraud Change Act, where each time an economist points out that the implementation costs will bankrupt the UK, they are told there is nothing to see here with future calculations, so move along.
If you put 'green' in front of anything the cost is zero as the money comes from the ever-growing, everlasting magic green money tree, apparently. Where in reality the average cost to each working taxpayer in green energy subsidies was a £500 tax bill in 2017, which increases to about £550 in 2018 and it will continue rising exponentially.