If your place is a house and not a condo, consider spliting the living unit to 2 units 1.5hp for faster and evenly cooling. Thereafter you you can switch off 1 unit.

If yours is a condo, ODU maybe a problem due to space.

It depends on the usage pattern.
If user use as 16C freezer ("near impossible" target temp) no diff between NON or INV. 
If user use at 25-27C achievable temp then yes inverter will save after it has achieved target temp. 

INV can cool faster if the unit has turbo capacity.
So for your case INV will save power if you do not run it at 16C all the time.
For living room INV 2hp still better..that 500 bucks difference in TNB bill can recover quite fast as bigger hp does use more electricity.

Lapsapda pricing:
2hp
AHX18VED 18K (5450-18760) btu RM2,287.00
X-Deluxe CS-XPU18WKH-1 19,000 (3,750-21,200) btu RM2,650.00
btwn the two they will work fine for normal sensible temp; but if ULTIMATE 16C FREEZER needed then get the pana coz btu spec higher.

for the 1hp one AHX9VED or CS-XPU10WKH (9700btu class) will work fine.
Ultimate spec can take a look at Hitachi RAS-SX10CJ (this one heavier coils in the ODU), clearance stocks RM1,799.00 for the bedroom https://www.lazada.com.my/products/hitachi-...4507648510.html

I hear Daikin not good already....but not sure how true. Another brand I heard is good is Mitsubishi

Firstly, since both are different hp, I believed the room size is also different. The 1.5 could be in an open space and the 1 hp in an enclosed room.

Secondly, is possible the 1.5 hp is undersized to room space. So the ac cannot achieved the 'set' temperature.

Thirdy, the right way to know the temperature is to use a thermometer. Place 1 in each room and away from the blower direction.

Does the cooling mode restarts after sometime or it remains the same till you off ?

I suspect it could be copper / room sensor problem. If you know diy, then unplug the sensor pin from the module and plug in again to try. Otherwise, you need to call the technician.

[attachmentid=11076677]

Ouch. Mine is exactly same as yours. The piping is one size bigger than what is required. Mine is 1.5hp but using 2.0hp piping. I thought of futureproof because currently I install for my tenant and I’ll be installing 2.0hp in the future for myself.

And the boss told me inverter has humming jet sound is normal?

Should have gone for the Pana 1.5hp that use 2.0 piping (12.7mm). There's one model I saw on Pana website.
Inverter *(in Aircon) should not whine.
Yup.. our inverters (mitsu and hitachi) just have wind sound at ODU. No whining wheeeee sound at the IDU (its not supposed to do the whine like industrial use inverters)
Your sharp is 4star or 5star ST model?
Inverters/VFD have different grades 

With modern panasonics, that would happen if you have econavi on. The aircond would also raise temperature if you put it on sleep mode. Is it possible you have on either of these?

I hate to admit this, but from experience it is true. Panasonic skew towards power savings so it is never as cold as Daikin, even when I set the setting to max on remote..its still hesitant to cool. Like, I set max fan, 17C the air con is like "you sure you want so cold meh? eh it use a lot electricity, come I slow down a bit save some energy". I am like.. eh hello, I want max cooling you give me max cooling la.

Limpeh using 2HP inverter Pana in bedroom. Based on measurement of room size & height actually 1.5HP enough. Now 2HP inverter Pana, just ngam ngam only.

Midea cheap and easy to spoil and parts? In 2015 I got MSN-09CRDN1 inverter models, 3 units used heavily because all in bedroom, until today no issues.. except workmanship not good the thing leak gas for 1 unit. Not the a/c's fault.

But best bang for the buck, HISENSE. If you want the most basic non-inverter aircon, limpeh will recommend Hisense over any Pana and any Daikin. The Japanese very expensive.

EDIT: Limpeh got Daikin, York (old cooling king good, current China mari Johnson control is rubbish), Hisense, Midea, Mitsu Electric, Pana -- love hate relationship with Pana.