3/4 npt isn't the same as hose thread - they may be close in diameter, but npt is a finer thread than hose thread. never the less, you can get cheap converters to go from 1/2 or 3/4 (often the same converter) to hose thread.
i tried the rain barrel idea myself, but to get the pressure I need to run my drip emitters, I would have to have the barrels some 15ft off the ground, which isn't very practical.
I'm looking at solar, but the best pressure pump i've seen (with the gph at psi I need) takes ~250watts/hr to run, so if I want two 1 hr watering sessions a day, I'd need to put 500w into a battery. a 100w/hr cell is roughly a grand, and it would need 5 hrs of bright sun a day just to break even. I can buy a lot of electricity from the oil company for a grand.