[Droxx]

It depends on how many you have.

160 per 2 (Full +1 recharge) (17.8pp per charge)
240 per 3 (Full +2 recharges) (13.3pp per charge)
320 per 4 (Full +3 recharges) (11.9pp per charge)
400 per 5 (Full +4 recharges) (11.1 pp per charge)
480 per 6 (Full +5 recharges) (10.7pp per charge)

I keep 6 on my single toon without jboots because it becomes nearly market cost to recharge them.