To recommend a robotic mower for a 3-acre garden, more specific details are required, as this is a very large area that exceeds the capacity of most standard consumer models.

To give an accurate recommendation, a company would need to know:

Terrain: Is the ground flat, or are there steep slopes? (Most mowers have a maximum incline limit).

Complexity: Are there many obstacles like trees, flower beds, or narrow pathways?

Layout: Is it one continuous lawn, or is it split into several separate zones?

Power: Is there easy access to outdoor power for the charging station?

Note: For 3 acres, you will likely need a professional-grade "GPS-guided" or "wire-free" model (like the Husqvarna Automower 450X or a commercial-grade unit), as standard models usually top out at 1.25 acres.