This depends too much on local policy, environment and your usage habits.
Assuming you want a grid-tied system...
E.g. 12.7kWh per day would work out around the 3kW system size here in Australia where we get an average of 4.2 sunlight hours per day over the year.
If you get a feed in tariff though it can be more complicated. It also depends on your metering arrangement. Ideally, you would want a high feed-in-tariff and a GROSS metered system to maximize your returns.
I would go with at least a 5kW system. This is what most typical families over here would need to (almost) cover their power bills.
NOTE: you can minimize your outlay if you get more panels but keep the same inverter. Talk to someone who knows how to design solar systems properly in your area and in compliance with local regulations.
In 2012, the average US residential client used 10,837 kwh per year. This would amount to 29.67 kwh per day. If we assume an even per hour use of this energy around the clock which obviously is not true, a grid tied solar system which as Hawaii has proven only works if the minority of customers have such systems, 95% efficient grid tied inverters and the 6 hours of usable sunlight per day that we have in southern US states, this would mean you would need 5.205 kw of solar panels which at about $3 a watt installed ( I'm being generous with the costs as it's often $5 a watt installed ), you're talking about $15,615 just for the panels.
If you miss the boat on the netmetering contracts ( Hawaii has already stopped accepting applications ) or don't fancy the prospects of paying a service fee in the future or the potential of selling to the utilities at a lower rate then you buy then you would have to be battery based which could easily triple your costs.
You would have to dramatically reduce your energy consumption before you can do away with the electricity bill. Fortunately, you can try conserving while you're still using grid power and only commit to solar when your usage is low enough, of course, by then your electricity bills may be acceptable to you.
The fact is, you would effectively be paying 24 to 34 cents per kwh for solar power while grid power would be 15 cents per kwh. It's only viable if you just want to say "screw you" to the utilities, you'll be on the losing end financially.
Get a quote for a system from a reputable contractor in your area. Do your own figuring on cost versus returns. Despite the raving reviews and encouraging sales pitches, payback is around 20 years. Most systems won't last that long, so this is a big bottomless rat hole that will not fill up, no matter how much money you pour down. However, government and utilities are quickly running up the price of energy, so even though it's not going to get cheaper, it will be a little more feasible. But why trade electricity bills for payments on solar panels?
Depends on where you live - for Europe, yield may vary between 250 and 900 kWh/year/kWp.
Also depends on whether you can feed back into the grid at a competitive tariff or need to set up a standalone (off grid) system.
Assuming 6000 kWh/year usage, a feed in tariff that'll be equal to what you pay for from the grid and a yield comparable to middle Europe (500 kWh/year/kWpeak), you'll need a system of 12 kWpeak.
However, that is just a housenumber - depending on your location and setup, anything between 6 and 24 kWpeak might be necessary - or more, or less.
I want to know how big a solar system i would need to get rid of electricity bills for good, we use about 1100kw -1200kw per quarter would that be 3kw system 5kw etc
