Thinking of building this 12'x16' fur shed w/solar panels for lights/heat and would appreciate any advice to improve it.
Good solar panel source would be beneficial also.
Thanks in advance for everyone's comments

The easiest option for solar would be the 4 panel kit from Harbor Freight with a better battery, should give the light you need, don't think you'll get much heat from any solar panel, don't think panels can keep up with an electric heater....other than insulating the heck out of it, and some kind of stove...you should be good.

I'm not going to be help on the solar system you to install. I can say I built a 16 x 16 line shack we will use every so often and has window facing south east and west. The building did cost more then 700$ was used material mostly and not insulated. The other day It was minus degree with highs in single digits. It took one hour to get the shack to 75 degrees and was easy to maintain that temp and could have hot it a lot warmer with a small wood stove.

My suggestion is to safe your money from solar panels and use another source for lights. Here the shack I built and if insulated it would get to warm in it.
I have a pic of the 1 5x6 foot window and the other side has 2 5x6 window those are plex glass. I know you lose heat from windows but I can tell you if you have sun out it gets so warm in front of those windows it crazy!!! Window are a huge factor in warming that shack. Just my view on the subject.

With solar, you will need and inverter and plenty of battery. Heaters draw quite a bit of juice, LED lights not so much. I have a cabin 16x16 with a 10x16 bedroom/bathroom. I am running 2 280 Amp hour and 1 300 amp hour lithium batteries wire in series with 800 watts of panels. If both ceiling fans and lights are going with the fridge and TV I can maintain power up to three cloudy days. I have a dual fuel backup generator just in case. You might look into a 250-gallon propane tank and use propane for heat.