I have seen no savings in doing DIY HA. Just the opposite. That said, I think the average DIYer is actually adding to their stable of devices and and equipment, and therefore adding costs, not actually taking away or saving anything. Let's look at it this way: a normal wall toggle switch consumes NO power when off. The load is diconnected. When replaced by a PLC switch, the switch draws power for its circuitry - albeit low, it's still more than the toggle switch - and the load is actually live in some situations due to the leakage current for the switch power (in cases where the PLC switch uses no common), which draws a little more power.
Then you add a PC and/or alarm panel running 24x7, charging a battery, blinking LEDs, running a panel, wallwarts, UPS, etc. Yes, all marginal, but MORE power. Now, how much do all those little quiescent power drains add up to? Yup, MORE then a toggle switch that completely disconnects the load!
Now subtract the savings due to turning down/up the thermostat, turning off lights, water temps down, etc. Also marginal $$$ in most HOME settings, and in many cases I believe it is difficult at best to have active circuitry that saves that much power to actually pay for itself.
Add costs of software, systems, upgrades, downtime, personal elbow grease, etc.
Total is (in my case) MORE than standard switches, no PC or panels, no wallwarts, etc.
But hey, I like the savings in other areas mentioned above, like bar tabs, etc... an ounce of prevention... hehe but htey don't apply to me.
Now I'm going around and replacing standard light bulbs with CFs, but not the dimmable kind. So no need for dimmers any more. If I'm interested in bright light, I turn them all on. If I only need mood lighting, I turn on a lamp or two, or only a couple low-wattage CFs instead of all of them. I'm hoping I'll see some notable difference on next month's electric bill.
My one gripe about CFs is the sensitivity they show to voltage fluctuations on the line. I live in the country and line voltage does ripple and fluctuate from time to time. Every little blip makes the CFs flicker noticably - incandescents didn't flicker as noticably. Then again, these are (relatively) cheap GE CFs.