Water heaters consume much of their energy just to keep a supply of hot water ready and waiting in the tank. The heat gradually leaks out of the tank until the heater turns on again to heat the water back up. To minimize this heat loss, ready-made kits for insulating water heaters and hot water pipes are available at hardware stores and building supply stores. Your utility company may also provide these at a discounted cost or offer a rebate on your purchase. Be careful not to cover the thermostat when insulating your water heater and always follow manufacturer's instructions.
Several methods are available for dealing with screws that tend to vibrate loose on covers of equipment such as chainsaws. One good fix is to remove the offending screws and wrap 1/2-in.-wide Teflon tape around the threads and then screw them back in. The tape will hold the screws tight, yet will allow you to remove them when necessary.