Transformer loaded current by changing halogen lights to LED lights, how many lights I can connect with my transformer?

12V DC transformer, 2.5A.

How many lights I can connect to my 12V transformer?
There are some people who reflected that why transformer load current appears overloading when they changed halogen bulbs to LED lights?
As you know, using halogen bulbs in domestic environment is usually input voltage 110/240v AC output 12v AC transformers, some people would think that the bulb connector between halogen and LED lights are same, so all they can do is just "Plug-in-play" replacement to LED bulbs. That is so wrong. LED light is especially designed with output 12v DC transformer, if you change your halogen bulb to LED light then you'd better change 12v AC into 12v DC transformer also. If you use input voltage 110/240v AC to 12v AC transformer halogen bulb, then it is fine, but still the wattage must be under the transformer's capacity limit, like halogen down lights, it is especially suits for 12v AC transformer.

How to calculate if the transformer is overloaded?
If the output of a transformer is lower than the consumption of the lights we have an overload situation.
This can be calculated using a formula:
Output of the transformer: Volt x Ampere = Watt
Consumption of the lights: Number of lights x Watt of the lights = Watt
Example:
Output of the transformer: 12 Volt x 1.5 Ampere = 18 Watt
Consumption of the lights: 10 lights x 3 Ampere = 30 Watt
Then we have an overload situation. The lights need 12 Watt more than the maximum capacity of the transformer. This situation will first cause dim lights and after a while the transformer will blow.
In this case 5 Halogen lights with 20 Watt each, they are connected to 1 transformer with an output of 12V, 2.5A.
Transformer Electric output: Volt x Ampere = VA or Watt
In this case 12V x 2.5 A = 30VA (Watt)
Halogen Power Consumption:
5 lights, 20 Watt each = 100VA (Watt)
The light is higher output of the transformer.
If the consumption of the over loading of the transformer,
We can calculate the output of the transformer with the familiar
Then you will have
This leads to a serious overload ratio of the transformer by factor 3.3 and the wiring is too thin by a factor of 4. The question in this case is: Will the transformer first give up and blow or the wiring start to burn. Here the wiring gave up first. During that period of the lights surely flicker.
If one would want to change from Halogen to LEDs in this circuit he would have to alter the Voltage. A white LED is usual driven with 3V, 350mA = 1W. A current limitation of 350mA should be within the circuit of every single LED.
On a transformer with an output of 30VA you can connect, theoretically, 30 LEDs. But the
circuit of the LED will also use about 1.5 VA and you have to adapt the voltage. So you can use around 10 LEDs on a transformer with an output of 30VA.

Transformer loaded current by changing halogen light to LED lights, how many lights I can connect with my transformer?
How many halogen bulbs, or LED lights you can be connect to your transformer depends of the minimum- and the maximum load of the transformer you use and the length of the cables from the transformer to the lamp.
For the first the wattage summery of all connected halogen bulbs- or LED lights should be higher than the minimum wattage of 20-35 W and a bit lower (5-10%) than the maximum wattage of the transformer you use. If the load is too low halogen remain dark, LED's start to flicker.
If it's too high the transformer gets hot, can burn through and the danger of fire is very high.
The second point is that the cables you use must fit to the current that runs through the wire. The longer the wire, the bigger the resistance of the wire will be, the warmer the cable will become, the higher is the risk of fire.
For example a 12V transformer connected with some lights (halogen or LED) with totally 105 W (VA) and a standard cableØ of 2.5mm² the maximum cable length should be no longer than 2m (already included a safety range). See also attached table.
When using LED lights with a 90% lower wattage in combination with a special LED transformer you have no flickering problems and also for a normal LED light installation the cable length is no problem.
So LED lights together with special LED transformer is always the solution to be on the safety side