I was told by a UK electrician who works here, that if your home has 3 phase electric in Thailand, to calculate the usage bill, they take the highest reading from one of the phases and then multiple it by three? Is that true?

 

(So for billing purposes, it is important to balance the load equally over the three phases)

Not for domestic as far as I'm aware.

 

The meter measures the energy consumed over all 3 phases and you pay for that.

 

It is of course always best to keep a balanced load anyway.

 

If you are an industrial user things may well be different and maximum demand and power-factor tariffs may apply.

 

For domestic 3-phase, the don't charge for going under the power factor

2 hours ago, digbeth said:

For domestic 3-phase, the don't charge for going under the power factor

what do you mean "going under the power factor"

2 hours ago, STD Warehouse said:

what do you mean "going under the power factor"

Electrical items do not all use power in the same way. An electric heater has a power factor of 1, some LED lights have a power factor of under 0.3, so for a generator they have to allow quite a bit more than the number on the box suggests. Electrical supply companies that use smart meters have the ability to measure this discrepancy. So far they are not charging for apparent power for domestic consumption. They may be charging commercial customers.

Quote

the power factor of an AC power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit, and is a dimensionless number in the closed interval of −1 to 1.

 

11 hours ago, STD Warehouse said:

what do you mean "going under the power factor"

it comes down efficiency and waste, going under means you are wasting energy and makes it harder on the grid, for industrial 3-phase power, there's an extra 'fine' for going under, so big industrial user has incentive to correct their power factor, this is usually done with a big capacitor bank (think batteries)