Answers start with S S

[smouse]

Two word answers and both words start with S
eg wind propelled - sailing ship

Settles many races

You need this if there is a power cut

[sarumite]

Settles many races .... Split second ?

[Aquagility]

Power cut - need Second Sight?

[sarumite]

You need this if there is a power cut ... Secondary System ?

[smouse]

not sure about the power cut one - sorry to be so fussy
I like split second though and thanks for the suggestions
Did wonder about solar source but think thats not quite right either

[nilesquimby]

I quite like a combination of those answers.
Solar System.

Niles

[TeeGee]

What about - Standby Supply

[smouse]

now dont give me too many choices - lol
I'll never be able to decide
Thanks all of you