* High efficacy

Efficancy is a technical term that is the ratio of USEFUL (for whatever the intended usuage is) to the amount of energy that is put into the device.

The term is often missued.

High efficent just means that it is somewhat more efficent than the standard or old version.

What is this being applied to.

* Occupancy sensor

A device that is used to detect the presents of people. Usually by sensing the infra heat given off by a person.

In commercial buildings often used controll lights and sometime the HVAC so that it is only on when people are present.

Sometimes used in homes to operate the lights in home in places like bathrooms and hallways.

* Manual-on occupancy sensor

I am guessing an occupancy sensor with a manual on override.

"My house is 60 years of age. When it was enlarged some years ago a new fuse box was installed and I've noticed there are bunch of blank boxes that look as though switches could be put in them. Am wondering how much updating is required along with the cost to bring this house's electrical elements to standard?"

I assume that this is a circuit breaker panel. And the spaces are space for additional breakers.

There is absolutely no way that anyone could make a guess of what the cost would be.

Just too many variables.