Motion sensor lights are almost as good a deterrent as an alarm system--and they can be had in solar!
After a series of burglaries at my former house, I put alarms on house, car, and truck. The weak point in alarm systems is that they are only as good as your local police department--and our city police 1-would not respond to alarms 2-would not take fingerprints 2-reported "unfounded complaint" so they wouldn't have to get up off their lead a##es and investigate 4-completed a report-number card with a nonexistent report number and the cop's name not listed, 5-had a burglar family member on the force, on day shift, in my precinct, and 6-finally got caught ignoring something like 28,000 911 calls in one year.
Ironically, one couple who had illegally entered, called the law on me one night when I slept through my car alarm being set off by a thunderstorm. I let the lawmen know in a hurry that the couple had never reported the repeated burglaries which occurred while I was at work. Police ran reports on the couple and they moved in a hurry!
WorldStart website was selling software and a webcam which could be set up as a room/house monitor, and they weren't expensive.