I don't know what percentage of global energy consumption can be attributed to heating homes and businesses. But it must be a substantive amount.

In Germany, most heating in winter is done by burning fossil fuels or wood.

For free-standing, single family homes, at least, I would assume that the amount of rooftop solar energy that can be captured using solar panels in summer would be able to provide much of the heating that's required in winter.

The true bottleneck seems to be storage.

Batteries don't work well for this:

The energy required for a year's worth of heating one home apparently is in the ballpark of 35,000ish kWh. To store that amount of energy in, say, Tesla batteries (which are said to have an energy density of about 260 kWh/kg), you'd be looking at 135 tons of batteries – costing around $8.5M.

Even with battery prices dropping, it won't be a viable option any time soon. (Besides, production of electric vehicles is already battery constrained.)

So, why not hydrogen?

Making hydrogen from the electric power provided by solar panels is easy. The stuff is flammable, and needs to be compressed – so that part does require some engineering to make it safe.

But then, you can store the stuff for pretty much as long as you like. Also, to transform the energy back into heat again, you burn it. This means that the basic principle of heating remains the same. The burner unit that used to burn oil or gas just needs to be converted to burn hydrogen. Or, if that doesn't work, you swap the burner unit. But the rest of the heating system can be left untouched.

It seems to me that such a system would offer home owners a way to become independent from utilities, energy politics and oil prices.

So, why isn't this a big thing already?

What other technology, if any, could be better suited to store solar energy in summer to use for heating in winter?

Thanks.