I started with a 55 gal barrel and a variety of water heater elements. It worked ok, but was a hassle to fill, to drain, and to store. Water and electricity seemed like an accident waiting to happen, so I've been looking for a smaller, safer alternative.
I recently switched to a pair of 240v electric heaters that my local Northern Tool had on sale. Each one has a built-in fan and 2 different heat settings. The smaller one has 3kw/5kw, and the larger one has 5kw/7.5w. They're meant to be hardwired, but I put a 30a dryer pigtail on the small one and a 50a oven pigtail on the big one. They each have a built-in thermostat (without temperature labels) that will allow them to cycle on and off.
The smaller one is plenty for 802. I can hook them both up to my 803 to give it a workout. Between them I have a variety of load sizes: 3kw, 5kw, 7.5kw, 8kw, 10kw, 12.5kw.
When I include the price of the pigtails, I've got $100 into the small one and $150 into the large one. But I also have heaters that can be used to keep my garage and shop warm, which is nice on days like this when it's -15°F.