Hi,
Thought I'd share an experience of converting a gas storage hot water system to be solar panel powered, without the need for an inverter or getting involved in high voltage AC. Being in Australia, some of the terms may be different, so forgive any confusion.
The LPG (Propane) gas fired storage hot water system I have uses around 0.3kg of gas a day, which is enough to be a worthy target in reducing my carbon footprint. I bought 3000W of "thin film" panels for $100. They make 60V and around 110W each. Of the 28 panels, I used 9. The thin film panels are superior for my situation, where we have many overcast days, and thin film perform well in the overcast conditions. The 9 panels makes 1000W in full sun, or about 350W on a bright overcast day.
The heating element is a 60V DC 500W immersion heater (eBay) on a 1/2" BSP thread. It is around 18 cm long and 15mm diameter. It's installed using the spare ports provided on the tank, with a 1" galvo pipe now running between the top and bottom spare ports. Using a T at the bottom of this pipe, the heating element is screwed into one side of the T to be running up the pipe. Convection moves the hot water up the pipe and into the tank. Make a sheet metal cover to avoid heat losses.
A DC 10a 60V thermostat is available on eBay. Use the DC fuse holders and switches from the recovered solar panels to save money on those.
Online calculators show the requirements for cabling. Solar panel connections from eBay.
Panels come in different voltages, and so do the heating elements. Elements are available in different wattages as well.
500W is heating enough water in a warm climate for 2 people.
The gas system remains in place, inactive because of the thermostat setting, for use in winter.
Next project: DC water pump to header tank using the remaining panels.
Happy days