I am not a dad but I was briefly a home owner. I kept the thermostat at 17 degrees Celsius. My sister and her kids would bring blankets when they came to visit.
I conclude that cheaping out on utilities is a universal man quality. Why turn up the heat when you have perfectly good skin to keep you warm? Why turn on the lights when you can squint and fumble around? Kids these days, I tell ya.
This philosophy is all well and good. Efficiency is great! Just make sure not everyone in your surrounding thinks of you as a miserable person to be avoided. Don't sacrifice a good existence to save pennies. Educate yourself on what is actually effectfull in saving money before demanding it of the people you love. Explain it to them. Never shout at them. Make damn sure your spouse have the same philosophy before implementing it.
I didn't even run the heat in my first apartment. It would get down to around 12C. On the weekends or if I was going to be spending a bit of time at home I would sometimes "splurge" and crank it up to maybe 18C. To state the obvious, yes I was quite poor.