Kunal, good energy meters should measure the POWER FACTOR, from which you can arrive at REACTIVE POWER. These are the two metrics people really care about : 1) POWER FACTOR , 2) Active (real) power, in Watts.

Once you know these two, you can calculate everything.

POWER FACTOR = cos(PHI) = P/S,

where P is the real power, and S is the apparent power.

Once you know S, you can find Q (reactive power), from

S^2 = P^2+Q^2

Why don't the power meters not give you Q ? Because, average home user doesn't understand or care about this. However, PF is the efficiency of your appliance, so, it is a lot more intuitive ... and, I care about PAYING LESS to the energy company !

A PF of 1.0 is excellent.

PF=0.99 is very common for a super-high-end power supply like Corsair (in a PC) ...

A 0.6 is for a pretty bad power supply,

A PF of 0.4 is a horribly inefficient power supply ... etc ...

So, this is a metric that is very easy to understand.

However, of course, very high-end devices from Fluke etc ... will give you everything .

In the end, it is a few formulas ...

Energy-meter is also called as motor meter the torque developed in aluminum disk is preposanl to active power. For detailed derivation of formula refer the,"Masurements & Instrumentation" by Golding & Widies.

There is no or very less usage of reactive power in houses and mostly mentain power factor near to supply's PF (0.9 to 0.95 is commonly supply PF).However Constructing and using (WATT+VAR) or (KVA+casO) in such a large number is not very fesible.Hower whwn home load become more then a certain limit Distribution companies start thinking of using meters for reactive power measurement

I am agree with Muhammad Haseeb.

To my knowledge household power meters only measure active energy, that is kwh and not kvarh. Therefore there is no gain for the consumer to install capacitors for PFC. Meters for industrial use on the other hand always measure both active and reactive energy, as well as peak power.