Times have changed. It used to be that a home with natural gas could have heat, hot water, and both stove top and oven cooking ability without any electricity. Whether you lived in an apartment in a large city or a farm in a rural location, if you had natural gas, you did not need electricity. Piezioelectric cells were added as a safety device to stop gas flow in case the pilot light went out preventing explosions. Piezioelectric cells did not need an outside electrical source to work. It used the flame / heat of the pilot light to function. Early furnaces used gravity to circulate heat within the house, no fan was used. Early stove tops and ovens did not even have pilot lights to work. Later ovens used pilot lights with bimetal thermostats to roughly hold to a given temperature. These appliances worked very well but were not very efficient.

Today things are different. It is all about convenience and efficiency. Pilot lights are generally out due to wasteful gas consumption. Stove tops usually have manual ignitors which again requires no external electricity. Ovens, for many years now, have an externally powered electrical ignitor which saves gas, no pilot light, and eliminates the combination of pilot light piezioelectical cell in the oven. In other words, no external electrical power means the oven no longer functions. High efficiency gas water heaters require a fan to force the flue gases to travel out the flue stack because there is not enough heat loss to move the gases out of the flue. High efficiency gas furnaces also do not have enough heat loss to move flue gases without the addition of an electrical fan. There is also the requirement of the main fan to blow the heat through the houses duct work. These new highly efficient furnaces also do not have a pilot light only externally powered ignitors. These efficient but complex furnaces require electrically powered sensors, relays, circuitry, and multifunction thermostats to operate. New high efficiency gas fire places also require externally powered fans for flue gases and heat distribution and electricity for ignitors and remote control ignition and temperature settings.

So, become familiar with your gas appliances. When you replace an old gas appliance with a new highly efficient one, they will most likely not operate without external electrical power. In fact, most twenty year old gas appliances already require external electrical power to operate.

And as already mentioned, natural gas appliances, if they are so designed, may operate on liquid propane gas only of if the jets are changed, adjusted, or modified.

You may be able to buy older technology gas appliances, which are still available, but your local building codes may not allow you to install them.