You cannot gain more power unless it is already available from the service drop which is either under ground, or outside where the wire come from the utility company to the pole that goes through your roof, and thus down and into the panel (breakers or fuses). You need to first start with the Amperage that is coming into your house. Most newer homes will have a 200 Amp service; some will be 150A (rare) or 100A and I have even seen 60 Amp service too. If you cannot determine the Amps coming in, look at the "Main" breaker. It'll have the amount on it. If you have 200A you are probably "OK" with adding a sub-panel. Extension cords are the least favorable way to bring power over to your grow. Depending on your local code, bringing a 30A or 50A line over would entail a: sub-panel; wiring (either in conduit or pipe, or in a Romex version) and the outlet/box, etc. where the new lines are connected from. A 50A, 240V sub-branch would be enough power to run just about everything possible that you'd need. If at all possible, asking an electrician would be necessary if you do not understand basic wiring. This is risky even if you know him unless you tell him you are gonna' install an electric, double oven in the grow room for Holiday cooking! He shouldn't question this unless he's a toker too. An older electrician (no offense) probably won't put 2+2 together, but you never know. A picture of your panel, with the cover OFF would help tremendously. There is an electrician on here that'll help too. I think we all can walk you through it, but ask questions unless you are 100% sure you know something is fact. Electricity and water are not a good mix, so safety here is paramount.