user13355: I'm trying to cut my esp8266 range down to about a meter to save power.  I know that I can adjust output power but I don't know enough to understand what a given setting will actually yield.
I can set zero to kill it or 20.5 to set max range, but what setting is appropriate for a meter or so?  Is there a rule of thumb?

user27653: The actual WiFi range is highly dependent on many more factors than just the TX power:

The antenna gain, directionality, and orientation of the receiver
The antenna gain, directionality, and orientation of the transmitter
The proximity of radio-reflective objects nearby (metal)
The proximity of radio absorbing objects nearby (humans)
RF Black Magic

In practice, test your situation by running a series of tests at lower and lower power settings until you get an unreliable connection, then bump it up a couple of notches from there.
Do not rely on transmitter power for security, however. You cannot stop someone from pointing a high-gain antenna at your device and communicating with it from a distance farther than 1 meter. TX power reduction should primarily be for energy conservation.

13355: <p>I'm trying to cut my esp8266 range down to about a meter to save power.  I know that I can adjust output power but I don't know enough to understand what a given setting will actually yield.</p>

<p>I can set zero to kill it or 20.5 to set max range, but what setting is appropriate for a meter or so?  Is there a rule of thumb?</p>
 27653: <p>The actual WiFi range is highly dependent on many more factors than just the TX power:</p>

<ol>
<li>The antenna gain, directionality, and orientation of the receiver</li>
<li>The antenna gain, directionality, and orientation of the transmitter</li>
<li>The proximity of radio-reflective objects nearby (metal)</li>
<li>The proximity of radio absorbing objects nearby (humans)</li>
<li>RF Black Magic</li>
</ol>

<p>In practice, test your situation by running a series of tests at lower and lower power settings until you get an unreliable connection, then bump it up a couple of notches from there.</p>

<p>Do not rely on transmitter power for security, however. You cannot stop someone from pointing a high-gain antenna at your device and communicating with it from a distance farther than 1 meter. TX power reduction should primarily be for energy conservation.</p>
