On Sat, OldNick wrote:

Well, having done a few quick calcs, I tend to agree, unless you had a
HUGE heating panel to get it active the next morning.

If solar heat is wanted at 0700 in a certain room,
an east facing window wall might be better than any
panels. There is nothing lower cost than ordinary
window glass.
My only kitchen outside wall faces SSW, and
in the afternoon the window makes almost heat as
a 1000 watt baseboard heater, and the window is
a little over a square meter.

With fuel prices apparently retaining the
high prices, there could be a huge market for
things like solar air heaters for inside windows,
just a decorative black pattern or simple venetian
blinds black on one side and white on the other.

Many heating panels and heaters are hyped
as radiant heat feels warmer even if the air is not
as warm, and the same goes for sunshine, except
sunshine is free (when it shines), and it can heat
the air just as well as the electric panels.

A window can provide about 5 times the
energy as PV panels of the same area, and that
is a lot, and it also makes PV seem not all that
expensive considering what electricity can do,
it is cheap grid power that makes PV seem
expensive.

Joe Fischer