An APS system is ok IF you are away from home often &/or for long periods. BUT if can water at least once a day not a necessary item.....
The heating pad is (in my opion) a important item.... as you said even the refrigator top is not warm... Also I start may of my seeds when the temperature is below zero outside.
Hope this helps

My advice is take advantage of your great, frost-free weather and learn to germinate before spending the $$ on either. Unless you are really deep into the Outer Sunset foggy part of SF, I would use the coffee filter in a plastic baggie method (see link) for the heat lovers and germinate outside for most of the veggies that can take some fog (my preference is to use flats). All the root veggies, the leafy veggies and squash and beans and peas and brassicas will germinate w/o additional heat in SF, although it can be slower this way if the sun disappears for days.

I grew plenty of veggies outside in Bolinas, the Haight and Oakland using these methods. Your main obstacle is that the humidity can promote damping off and other diseases, so an occasional spray of dilute hydrogen peroxide or watering with weak chamomile tea is a good preventative.

It's not that heat mats aren't a good aid when the marine layer rolls in, they just aren't a necessity. APS always has seemed an unnecessary expense in coastal CA.

Here is a link that might be useful: faq: baggie method

Thanks! That's great to know you were able to germinate outside (I am thankfully in the Haight, not the Sunset).

For germinating outside, I'm assuming that putting them anywhere that doesn't get direct sun is okay? Did you just put the flats out there or did you use any kind of cold frame?