No. The reason is that power analysis when it comes to cryptography, relies on certain signatures, like a specific frequency of signals, so theres still possible to detect even if you have large devices running.
Your "defense" is more like trying to mask morse code using white noise. Yeah, the morse code may be indistinguishable for a human, but with technology, you could dig out the morse code out of the garbled sound signal.
A better defense is to use a UPS. Assuming the location of the computer is "secure", as your original defense assumes, you can in other words place a UPS there. Of course, the UPS should be a "online" one, eg not relay based, but a UPS with a battery, charger and inverter, constantly connected.
Such a UPS, will smooth out both current consumption, and voltage spikes and inpurities, both at input and output, since there is transformers that will smooth out the AC.
If you want to go ultra-ultra secure, you could arrange for this, note that UPSA and UPSB must be extremely large ones that can drive your PC for several hours or even days. UPSB must also be larger than UPSA, and also be able to supply more power than UPSA, and also UPSB must charge to full faster than UPSA consumes:
Computer --> UPSA --> SwitchA --> UPSB --> SwitchB --> Wall socket.
- Initial state SwitchA off, SwitchB on.
- When UPSA start to get discharged, you first turn off SwitchB, and then turn on SwitchA. Now UPSB will charge UPSA. After a while, you will end up with a discharged UPSB and a charged UPSA.
- Now, turn off SwitchA and turn on SwitchB. Now UPSA will consume to your computer, while UPSB will charge.
- When UPSA have discharged, your UPSB should have enough charge so you can turn off SwitchB and then turn on SwitchA. And so on, and so on.
Here, a automatic switchover and charge management can also be done so UPSA/UPSB never fully charges/discharges, to save on the lifespan of the batteries.
Note, that in the above solution, the computer is never ever directly connected to the wall socket, there is at least one open/off Switch, either SwitchA or SwitchB, between both. This will also cause significant wear on the UPSes, so you need to weight if you really want to go ultra-ultra secure.
A simpler approach, that still is ultra-ultra secure, is to use a single UPS that you unplug from the wall socket when you are "going secure". You can also implement this idea with a laptop, where the laptop becomes the "second" UPS.