I am guessing you are somewhere in the southwestern US - although quite a few other places have both snakes and scorpions.
If you have access to propane the most efficient water heater you can get is a tankless unit. If you get a power-vent unit you will not have to install a full chimney (flue) either as it may be directly vented. These are a bit pricey as related to tank-type units but they are over 75% (at least) efficient as compared to 65% (at best) for any tank type. As well, you have no storage waste, no elements to clog or replace and as they are also relatively tiny as compared to tank types, they may be safely installed hanging on a wall or in a closet **IF PROPERLY VENTED**. They also produce hot water endlessly.
We have had a Bosch Aquastar for these last 15 years and it has done very nicely for us.
The first link is for a smaller unit. The second will do fine if you don't run more than two showers at once.
Installation is no more complex than a tank-type heater, and easier than many of those as the fittings are more convenient. NOTE: Unless you are familiar with propane, working with propane and installing gas fittings - where a mistake can go *BOOM* in short order - I suggest you consult your propane supplier for the gas-line hook-up. Many will do it for free - certainly ours did.
You can reduce the calcium build-up by using a water softener. However, those systems (or those of them that actually work) replace calcium salts with sodium salts. These will not build up in the water heater, and the water is great for washing and showering - but it is generally thought to be unhealthy to cook with or drink softened water and it is absolutely terrible for irrigation or for the soil in general. And if you are on a septic system, you are dumping salt into the ground where it will eventually get into the (shallow) aquifer, making that toxic forever.
Good luck with it!