You might be surprised - a small size (3x3) multi-arboretum runs pretty well on a single 1 LP boiler providing 2 MJ/t. I made a fun little setup where the boiler runs off of planks from the farm processed by a TE sawmill. It only consumes a single log every 3.75 minutes while letting the farm run at near top speed under 1.4.7 mechanics.
It's not quite enough to keep up with the tree growth, but almost... And then again, the multi-arboretum is getting less energy drain per action
and less actions to execute per tree chopping in 1.5.1, so it should make do with noticably less energy than before. A vertical wind turbine could probably let it run at full speed constantly, if it was built in a high place.
Obviously a horizontal windmill at sea level is still going to throttle quite a bit, as it'll average around 0.6 to 0.7 MJ/t. Depending on how the changes pan out, you might be getting half or a little less than half speed.