I've been asking the same question for a long time, and have come to these conclusions:
Alcohol extraction (95% Everclear) is probably the most efficient extraction, but is too much work and expense.
I'd guess it's about 95% efficient.
Leaving the decarbed herb, ground to fine powder, in the oil, and putting it into capsules, or baking it into cookies, is 100% efficient, and the method I have been using.
For myself, I've defined "one dose" to be 0.5 g herb, which for 16% thc herb is about 80 mg thc.
About 0.2 g herb in each size 00 capsule is the strongest unstrained oil that goes easily into caps using a candy dropper.
For 16% thc herb (160 mg thc for each 1000 mg herb), that's about 32 mg thc each, so these are 0.2/0.5 ="40% Pills."
I use these caps for sleep, and after many years of use, need to take about 4.
I also make slightly weaker caps, "30% Pills," each containing 0.15 g herb, to be able to fine tune dosage.
Recently I tried an experiment to try to figure out how much potency is lost when straining an herb/oil mixture.
I used an Ongrok infuser (a smaller version of Magical Butter Machine) @ 160 F for 1 hr, followed by 2 more hours of NoHeat infusion.
I let the mixture settle in a beaker for 3 or 4 days, and then poured off the liquid, leaving the solids behind.
(I could've strained immediately, but chose the settling method instead)
Next I used 3 small batches of 95% Everclear and vigorous hand-stirring, followed by hours of settling and pour-off, to try to glean any remaining potency from those solids.
The third stirring produced a liquid that was clear enough that I suspected near zero potency remained.
Then I boiled off the alcohol. (There exist devices to reclaim larger volumes).
Some potency did remain, and I combined it with the original strained oil.
I was a bit surprised at how little potency did remain in the strained-out material, and I'd guess the oil extraction is almost as efficient as the alcohol extraction, 90-95%.
The straining process increased the concentration, from what I've defined as "40%" for the unstrained oil, to about 70%.
That's concentrated enough to be called "oil tincture," and put into tincture dropper bottles.
One 70% cap contains about 0.7*80 mg thc = 56 mg thc, and will hold about 33 drops at room temperature.
That means each drop is about 1.7 mg thc.
Putting this into baked goods is easy.
Here's a recipe for the small batch Ongrok machine.
(Magical Butter Machine and the other brand machines probably need 1.5 to double this recipe to reach the "minimum" line)
56 g Decarbed herb, ground to fine powder
56 g lecithin
148 g Any Oil
[my actual test used (47 g herb) + (47 g Lecithin) + (122 g Coconut Oil)]
In the future I'm likely to use this recipe with a single small rinse/reclaim from the strained-out herb.
Decarbing reduces weight slightly, increasing %THC, and probably compensates for slight extraction inefficiency in the calculations
I don't think type of oil matters much, and some oils like olive and avocado can be kept as mostly liquid in a refrigerator.
