Where I live there is a big (ca. 2x) increase in the cost of electricity for a small business vs a residential house. My electric bill for my barn and arena sometimes is over $250/month (in the winter) which is what the cost of the house electric bill is.
Granted, I have a heated water trough in the winter and keep the tack room at 40 degrees and almost all my lights are fluorescent but if your friend is paying business electrical rates, her costs might be higher than you think. The electric company tells me that I could get residential rates if I put a kitchen and bathroom in the barn but that would mean another septic system and I already had to drill a separate well for the barn.
Mary in Western NY
http://www.bpequine.com