Like "wpsellwood", I also take an empty bucket(and a long-handled scrub brush)around with me when I need to dump, clean, and refill buckets. Also--I use the small(@ 2 1/2 gal.) heated buckets inside, the larger(5 gal.)ones in their outside connected runs, so I don't have to carry the heavy water(each gallon weighs about 8 lbs., you know!)back and forth when they are shut in at night during really cold weather, but can stay 'shut' outside on nicer days(so they can't simply use their stalls as the bathroom!)
If you read the info in the catalogs(I've ordered all of mine from livestock catalogs...Jeffers, Valley Vet, KV...no TSCs around here!), you see that these buckets don't individually pull a lot of wattage--though I know that if you have a LOT of them, the total could be high. I have 6 in operation in winter, plus one floating 1000 watt tank heater.
Another thing that REALLY helps is plugging them into a timer; it is especially helpful at managing the cost of operating the tank heater! I set mine to coordinate with my 'Time of Use' electric rates(my house is all-electric; for years, we heated ENTIRELY with wood to be able to afford to live in it...but about 9 years ago, my rural electric co-op began offering Electric Thermal Storage(ETS) heating units, and 6 years ago, when they offered one that would work w/ hot water baseboard units, and would install the system for free, and I could pay off the actual unit interest-free over 5 years, I opted in!) With use of these kind of units comes TOU electric rates....high during the hours of greatest use, lower during more 'off' hours. It does help...still, my electric bill triples or quadruples during the winter...so I try to do EVERYTHING I can think of to minimize use, esp. during the 'high' rate hours. Anyway...plugging the heated buckets/tank heater into timers is a BIG help! I use extra HD outdoor-rated extension cords, plug two buckets into each, so only 4 timers needed, including the one for the tank heater, which has its own plug, and an outdoor-rated timer, which I put under a waterproof cover, anyway! Best are timers that have 24/hour settings. I got mine at Walmart; they aren't horribly expensive, and most have lasted several seasons, at least.
I do think that the heated buckets *can* keep the water at a temp warmer than some like; using the timers, so that they aren't heated ALL the time, helps with that, in my experience.
Margo