I have a COTS solar battery charger that has a number of different LEDs identifying the battery level, if its charging, etc. Its going to live in the shed, so 99% of the time no one will see its pretty array of lights. Would it be OK to replace these LEDs with diodes and would it save any electric? Thanks in advance.
Without a schematic it's pretty hard to be sure, but 'nine times out of ten' the LEDs could be snipped out with no effect on the functionality. Replacing them with diodes would stop the light emission, but would almost surely use more energy, or could even possibly damage the circuitry. That's because LED driving circuits usually present a fairly fixed voltage with a resistance that's designed to cause a certain current to flow through the LED.
For example, a 3.3V circuit driving a 2.4V LED to 7.5mA would use a 120\$\Omega\$ resistor. If you replace the 2.4V LED with a 0.7V diode it will draw almost 22mA or almost 3x the current (and therefore, since it's all supplied by 3.3V, almost 3x the power, and over a given time period, 3x the energy).
The most suitable component will be zener diode, in case you don't want to generate light. One 3V3 diode may do the job, watch for the current rating. No, you will not save any energy by replacing LEDs by zener diodes. On the other hand, taking the LEDs out you may miss important information about the actual state of your equipment. Is it worth?