Need suggestions for what would be proper stat for 2 heat 1 cool system. Currently using white rodgers thermostat, which lacks backlit feature and has no battery backup for power outages. Is a 24v wired system. 7 day programmable features. Thanks

You have a few to pick from. White Rodgers and Honeywell both have back lit and battery backup models. Cost will be a factor since the more you spend the more accessory toys you get.

If you have a heat pump be sure to get the heat pump thermostat. They make 2 stage heat thermostats for just electric strip heat and gas furnace heat that will not work with a heat pump.

Look at the vision pro 8000 series by Honeywell. Good source of info Furnace Filters, Air Conditioner Filters, Air Quality - iaqsource. Presented nicely.

This pretty much explains it: Spectral Curves

Each material (Silicon, CuInSe2, GaAs) has spectral response.

The sun has a particular irradiance. Solar cells are tested at 25. Deg C with a lamp that emulates the AM 1.5 Global spectrum. AM = Air Mass. AM 0 would be above the atmosphere.

You can actually calculate the short circuit current of a solar cell knowing the AM 1.5 Spectrum and the spectral response of the solar cell.