Yes, very true, but an electrical system also pays off too.

I'm considering a 48VDC system in the house. I'm going with 48VDC because I can get stuff made for telcoms that will run off of 48VDC. Even including air conditioning systems and power supplies for computers. Inverters made for 48VDC battery banks are more efficient than ones made for 12VDC.

As for batteries, either buy large flooded NiCd or flodded NiMH, lead-acid for fork lifts, Telcom lead-acid or NiCd batteries. Deep cycle batteries made for solar, golf carts, tolling, and AGM style are all short lived in comparison, 300 to 600 80% Depth Of Discharge (DOD)cycles. A good fork lift battery will come with a 7 year warranty and be expected to handle 1800+ 80% DOD cycles if properly maintained. The automotive Saft NiMH and NiCd batteries will do 3000+ 80% DOD cycles if properly maintained. The nice thing about forklift batteries is they are made out of fully contained cells so replacing a dead cell is easy. The bad thing is a 500AH cell still weighs allot. I don't know much about telcom batteries except it isn't unusual to see 20 year warranties. Also 400+lbs single 2V cell weights are not unusual. On the other hand they aren't designed for daily cycling.

Another thing on batteries: The lower the percentage of the full capacity you draw from it before recharging, the longer it will last. Lets say you figure you need to draw 80AH/day a day and you want 3 days reserve capacity. The minimum battery you should buy is 300AH. That would give you 80% DOD after three days of no recharging. Now if you bought a 600AH battery, you would only draw it down 40% rather than 80%. Given what I remember this will likely give you around 2.5 times the life expectancy. You also now have 6 days reserve.