There’s an element of cost and an element of reducing our footprint here.

Be that as it may we are going for a 10 kW south-facing array and 24 kWh battery so I’m hoping we can do the heating on our own juice in all but a couple of months. At least if my calculations hold.

But I’m sending four kids into the world. I’d like to do my bit to avoid making it worse for them, so it’s ok if it all together ends up costing over the next 5-6 years.

Immediate costs are not the only element in the equation. Electricity can be sourced from many sources, whereas fossil fuels don't have an alternative (as in, if oil becomes hard to come by, too bad. Whereas there's many ways to make electricity).

Well, oil prices will surely go down, soon, and the good news is the weather changes that cause all those heatwaves also increase the efficiency of solar.