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We've been off grid for decades, it's no big thing, you get used to it. For your initial question, your "3,782 system" could either mean 3,782 watts per hour produced by the panels or someone with a calculator has figured that's how many watts you'll get per day. That number can't really be defined by what you've given us. Most frequently, though, folks refer to the systems by their output amount.
Usually, the solar sales folks will tell you to get your electric bill and then they size the system to match what you were using on grid power. Generally, that system will be huge because when you're attached to the grid you aren't as careful with power as you are when it's a limited resource. When you're off the grid, you will find that all your light bulbs will be curly bulbs or even more efficient LED bulbs. The dryer is a clothesline or if you do have an actual dryer, it will be gas. The stove and oven are almost always gas. The new refrigerators are efficient enough that they can run on solar systems. Your electronics will all be attached to an outlet strip where they can all be switched completely off when not in use or there will be several outlets in the house which have switches that will allow you to turn the outlet off. Folks on solar electric systems use a lot less power than those on the grid.
If I have a 3782 watt systems, could I burn 37 100 watt light bulbs while the system is in full sun? All the bulbs would be putting out full light?
Yep, that's the right idea. Assuming that the system is new, in full sun, directly facing the sun, with clean panels, and no system losses, etc. So in effect, that's the best it could ever be, in a perfect world.
In practice, this not being a perfect world, as panels age their capacity gradually declines (est. 50% after 20 years), the intensity of the sun varies by the season and time of day and cloud cover, fixed panels will almost always be at reduced power because of their angle to the sun, dust and dirt on the panels reduce power output, simple systems are limited by the weakest panel's output (so if one panel is shaded, all panels lose power- better systems avoid this with micro-inverters installed on each panel), etc. That's why I referred you to the online calculators that incorporate heuristic rules, because no simple formula encompasses all the variables that are actually involved. It really takes a full page to work up all the relevant factors. Or a solar panel vendor can assist you with the calculations.
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Originally Posted by oregonwoodsmoke
So, add up the watts needed for things like the fridge and computer and TV and keep the total under 3782 watts? Allowing for the fact that everything draws heavier when it starts up.
As a crude calculation, that's the general idea. Practical planning requires much more comprehensive calculations. Typically off the grid the power generated by the panels is used to charge the battery bank, and power from the batteries is used to run the power inverter that supplies AC power, so there's a sort of shock absorber in the system that helps with start-up loads. And there's some systemic loss due to the battery chargers, etc.
As a crude heuristic, napkin doodling style, I'd say cut that figure in half for an off-grid system. For a system rated 3782 watts capacity you might figure on actually being able to use 1900 watts x the number of full sun hours.
This is why grid-tie systems are really the way to go for a lot of people. During the day, when typical household loads are lowest, you bank your excess power into the grid. During the night, you pull the power you need down from the grid. If you do this, then any size system is OK, and you buy as much as you can afford to invest in. It provides whatever percentage of your total consumption that it does, and you buy the rest from Helco. And in that scenario, you can also build your system capacity a piece at a time, as your budget allows.
Thanks, everyone. That's the point I am at. The crude calculation. I'm just trying to figure out the vocabulary.
For a quick, easy reading book for learning about solar energy check Got Sun? Go Solar from PixyJack Press . You might find it at the public library - that's where I first found it. Everything is explained in plain language so you can learn the vocabulary along with the basics of solar.
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