To assess whether you need an Easifit kit, try to answer the following questions:
Do the cables from the solar panel system go directly to the consumer unit / fusebox?
If so, you will need an Easifit kit to install Wattson. Refer to the Easifit Installation page.
Do the cables from the solar panel system go to a junction box which also contains cables from the meter?
If so, you do not require an Easifit kit as the junction box (also referred to as Henley Block or cable distribution box) lets Wattson work out whether the current is flowing into or out of the house. Refer to the Henley Block Installation page.