We're regarded as elderly but our thermostat is set at 4C and turned off completely during the night, it hasn't come on since the snow and we're not cold.
Wool clothing and a hot water bottle are the answer. And no, we don't look like M. Michelin!
That's insulation of the body, insulation of the house is even more important and free for the elderly. Sadly we can't take advantage of that, we insulated ours many years ago when it cost.
The power companies won't be gleeful about our payments either, we use well below the local average of gas and electricity.