Ouch! Mine first PW was capped and when the second + B/U gateway was installed, they were uncapped then. If there was a DNO charge, it was hidden in the very competitive quote. I guess it varies upon area.It'll be capped to 3.6. Partly due to time taken to get DNO approval for 5kW. The installer's experience is that they sit on requests for the full 9 weeks, then charge a few hundred quid for the priviledge. Given that the invertor is limited to 3.6kW, its a marginal benefit to uncork the PW. It's something we could do retrospectively. We're having a backup gateway too. I think if we were in an area where we had regular power cuts, we probably would do it.