These heat span graphs represent how heat is dissipated from a certain height and inclination. Do not associate this with the area that you will be experiencing warmth and comfort.
We recommend 1 heater for 2 persons.
Table for 2 persons - 1x Stellar Horizon 2000W heater.
Table for 4 persons - 2x Stellar Horizon 2000W heaters.
For closed or covered areas you would need less, 1 heater for 4 persons.