An LED upgrade is expensive. Most of our fixtures use two 921 bulbs each. The payback is in length of stay when on battery only.
Each 921 bulb burns 1.2 amps each or 2.4 amps per fixture.
Replacing them with LED pads (or High Power SMD WLED-xHP9-T (194 type) 360 degree Wedge Base bulbs Specifications
reduces the power requirement to 0.1 (yes, 100 milliamps) per bulb or 200 milliamps per fixture.
That is better than a 10 fold improvement in battery life (lighting only of course).
Good info in this thread. LED 12 volt lighting: Long term results
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