Don't believe solar sellers. Do your own research.

[papaof2]

In the next 14 days, we have 4 days of "Partly Cloudy", one day of "Mostly Cloudy" and nine days of "Showers" or "Rain". I seriously doubt that a solar salesperson would tell you that you need a minimum of 14 days of autonomy (battery power) or a generator but you would certainly need at least that much autonomy or a gen if you were in this area and were "totally solar" - or you would have a long list of: "This gets power 3 hours a day." "That gets power 5 hours a day." "Those only need power on alternate days: the left column on odd days and the right column on even days."

Solar power is NOT the always sunny skies of the ads they provide or the images in the minds of many of the proponents of "green" energy.

I should probably add today to that list and make it another day of "Showers" in a 15 day list. At 10PM, the solar walkway lights were already dark because there had been so little sun today.

[techsar]

Never have consulted with the so-called solar experts, but I believe you're correct about the lack of disclosure for longer term outages. Most sales people are only concerned with the quick sale, not the actual needs of the customer. And that is if they are even aware of the realities solar users face.

I do know that we only got 3.6 kwh of power today...heavy clouds and scattered showers, with the same forecast for the next several days. Not too concerned with 38kw of battery backup and a generator to back that up. Without prioritizing loads this is good for over two days (this includes running two mini split ac/heat pumps, well pump, lights, fridge, two freezers) and quite a bit longer if we cut back to bare necessities.

[papaof2]

Nothing quite as good as the voice of experience :-)

I'm sure folks get tired of me pointing out some of the ridiculous "solar deals" I see but maybe the hints will surface when someone tries to sell them "And it includes two full days of autonomy!"

[feralferret]

For the present, I'm only trying to get setup for a few lights, charging for phones, and power for a radio as needed. I will be setting that up where we are moving once we get moved. I already have a couple of solar floodlights that I will mount inside with the solar panels on the south side of the house. They have a remote control so I can control the output level and on/off/motion sensing mode.

Many of the reporting stations on Weather Underground display both the current and a historical chart for that day for Solar Radiation watts/m². Factor in panel efficiency, etc, and this can provide an estimate of what you can expect to get from your setup or what size you are going to need to provide enough power. You can also look at each day in the past and get an idea of what a realistic average would be.

[papaof2]

I think it's a safe bet the solar sellers never refer anyone to that information :-(

If the folks did any calculations at all, they'd probably blow whale-sized holes in the seller's proposal.

[papaof2]

There's a wunderground station maybe 2 miles from me that includes solar intensity in the data. Today's peak was 77.1 watts/sq meter - a bit short of the STC of 1000 watts/sq meter :-(
But that was expected with "Showers" and "Rain" as the forecast for much of the day.

77.1 / 1000 = 0.077 or 7.7% of the panels' rated power. 250 * 0.077 = 19.275 watts for a couple of minutes. That won't do much for your fridge but it might help charge a battery for some small LED lighting.

The shed lighting is 3 LED strips with a total draw of 1.78 amps @ 11 volts or 19.58 watts. I use a DC-DC converter to drop the battery voltage to 11 volts because it provides enough light and the "12 volt" LED strips should last almost forever. If the battery charging is very efficient, I might get a minute of lighting for each minute of solar power at that intensity. The panel out there is 30 watts so today's power peak would have been 30 * 0.077 = 2.31 watts. That's why the battery AH is keyed to the expected use of at most 40 minutes 3-4 days a week in summer and 1-2 days a week in winter. If I needed light out there daily in winter, the solar panel would be 100 watts and the battery AH would be maybe 4 times as large - even with the LiFePO4 battery.

As you said: know what the real world can provide and live within those limits.

If we had a SHTF event, I'd consider running a gen long enough to make a 5 gallon grill-sized LP tank into a small stove that will fit inside the firebox of a fireplace (including a stovepipe into the damper opening) and I might be charging battery powered saws (chain and circular) to be able to cut up a neighbor's old and probably very burnable wood privacy fence. You need to know what your possible supplies might be...