A panel of finance experts speaking at InterSolar Europe have given news of the Tesla-SolarCity deal mixed reviews ranging from "silly" to "brilliant".

Dirk Michels, a partner at the law firm Ballard Spahr suggested the companies could both clearly benefit.

"I think it's a brilliant move," he said. "First of all the financing costs for SolarCity will come down; they're going to have the backing of Tesla and its balance sheet and I have no doubt their balance sheet is increasing with the new Model 3 coming out.

"It depends on whether they [Telsa] are going to have production problems. But financing costs for SolarCity will go down. And we're going to see totally new products in the market. Who says you cannot have an energy lease where you have a combined car and solar and energy storage system all in one lease? I have two neighbours who bought a Tesla, and they don't have solar. Now SolarCity is going to be Tesla, they're going to have solar within the next year and a Tesla Powerwall," he suggested.