When I bought my house in 1995 we immediately undertook to modernize. This included revamped wiring and cat5 and coax to every room, but it also included new windows for most of the house, blown insulation, attic blanket, and special stuff for between the beams that hold the roof (so a balloon-frame house can still "breathe").

Now I'm about to refinance and was considering upgrading from forced air gas heat to a ground source heat pump. I'm unsure, though, if I have the lot size to deal. I'm also considering solar collector panels or solar water heating, but that's probably just for show in our unusually cloudy city.

Have any of you done anything like this before, and perhaps have advice to offer?

At my old house in Maine, we used to have a solar hot water heater. Basically it was a big solar panel and an electric pump that would pump this oil-like substance through the panels. The sun would heat the oil in the panels, and the pump would circulate the oil down to the tank around the water. The tank was super-insulated, and it was pretty efficient, even in the cold winters in northern Maine. IIRC, the unit was pretty expensive at retail, but we bought it at auction for under $500. I think that it would do okay in Pittsburgh, but you could probably ask around to be sure. It would have to be fairly cheap to really save a lot on hot water bills, unless you had hot water heat in your house.

I haven't had any experiance with a ground source heat pump, but I have heard they are pretty efficient.

Well, my gas bills for the last 2 months, which is just gas dryer and gas hot water (and very little gas stove/oven) total like $50, so, really I expect this will be at a loss.

It's the heat pump that I'm really interested in.

I have a (very) old-school solar hot water heater.

It works great, and I leave it on 8 months out of the year.

It consists of two tanks. The primary tank has a thermostat-controlled
pump which cycles the water to and from the roof collector whenever
the pipes on the roof are 20(?) degrees warmer than that on the tank.
In practice, it kicks in for about 15 seconds every so often. Maybe
every 15 minutes on a hot summer afternoon, maybe every few hours
on a chill autumn morning.
Supposedly, it will also circulate if the water in the array drops close to
freezing, to prevent ice crystals from forming and bursting the thin pipes
in the collector. I've never tested this, as I drain the collector (a five
minute process) for the 3 months where there is any conceivable chance
of a freeze around here.

The primary tank feeds into a secondary tank which is a "normal" hot water
heater; so it can kick in and boost the temp if the solar tank isn't quite hot
enough.
In practice, this never happens, and I have twice the hot water of a
"normal" system and yet a virtually non-existent gas bill.

I've been told that nobody makes these "active" systems any more due
to the fact that people don't want to have two big tanks.
They've been replaced with "passive" systems consisting of a big
honking pipe which sits on your roof and is effectively the second
tank. People who use this to heat swimming pools love it.

Personally, in earthquake country, I really don't want 400 pounds of
thick pipe and water sitting on my roof!
I'll stick with my lightweight, low-impact active collector, thank you very much!

(And yes, you better believe I have both indoor tanks securely strapped to
the walls. You don't want those babies doing the tango during a quake!)

I don't know what it cost 20 years ago when it was installed, but it only seems
to need minor maintenance about once or twice a decade!