I'm not profligate in my use of electricity, but the utility company says I use roughly 500 kilowatt hours of energy per month for all household needs. A kilowatt hour is 3.6 million joules. So, at 500 kilowatt hours, I use roughly 1.8 billion joules a month. Thus, even if all the energy associated with a bolt of lightning could be captured and used, it would keep my house going for somewhere between half a month and five and a half months . The total energy in a lightning strike is partitioned in several ways.
Energy is radiated away in the brilliant flash of light.
Some energy heats the air in the immediate vicinity of the lightning channel, and some generates the low-frequency sound waves we hear as thunder. The remainder, electrical energy, is only a small fraction of the total. To be fair in answering the question, we should consider only the electrical energy available at the bottom of the stroke for capture and storage. For an average stroke that is probably less than ten million joules. Capturing and using the energy in lightning has been the subject of many imaginative proposals over the years, but there are practical reasons for not even trying.