Float arithmetic vs. int arithmetic - is there any power penalty?
It depends on what your processor is doing while it has no real work to do:


If you put it to sleep, then yes, using floats will keep the CPU awake for a longer time and burn more energy.
If you are instead doing busy-waits (e.g. with delay()) it should make no difference, since the CPU is busy 100% of the time anyway.


Update: According to your update, it seems your program never
sleeps. Then I would expect no substantial difference in power
consumption between using floats or ints. As Majenko said, there can
theoretically be some small difference depending on the number of
transistor transitions involved in each instruction (and, I would add,
the capacitive loading of the involved transistors), but I do not expect
this to be very significant.

If you are really concerned about the consumption of your Arduino, I
would suggest you use it only for prototyping, then move your code to a
bare ATmega (or maybe even an ATtiny) chip. Also, add at least one call
to sleep_mode() inside your main loop. Each such call will put your
CPU to sleep until the next timer interrupt, which typically happens
every 1024&nbsp;µs. There is a lot more to say about power savings, see
for example this excellent writeup by Nick
Gammon.

Edit: When trying to minimize power consumption, one of the very
first things to do is figure out how much work has to be done, and make
sure your program never does more work than required. In your case, this
means you have to know how often your main loop should execute, and
prevent it from running more often than needed. For example:

#include &lt;avr/sleep.h&gt;

const unsigned long loop_period = 5;  // run the loop every 5 ms.

void loop() {

    /* Sleep while waiting for the next time slot. */
    static unsigned long last_time;
    while (millis() - last_time &lt; loop_period)
        sleep_mode();
    last_time += loop_period;

    /* Actual work goes here... */
}


If the actual loop work takes significantly less time than the loop
period, your CPU will sleep most of the time, leading to significant
power savings. Then you can start digging into more advanced
power-saving techniques like those mentioned in the article linked
above.