No, they’re not. Such heaters are designed for small spaces, like a living room or a bedroom that's either big or small. Even the best heaters that are portable will not be sufficient for the entire house.
If you use a portable heater for the whole house or an area bigger than the heater’s capacity, then it may raise your electric bills by a LOT. This is why it is not an efficient way to heat your house this way.
For the whole house, you will need a heater that fits into your HVAC system. But if you’re using the portable heater as a form of supplemental heating, then you’re good to go.