What size generator would be needed to run home of 1800 square feet?

What size for lighting only?

min. rpm's (on generator)for each application?

Torque required to started this generator?

Torque required to keep it running?

Most small commercial and consumer gensets are spinning at 3600 RPM. You can purchase 1750 RPM sets.

Add up the watts on all the lights such as (3)-60-Watts and (2)-100-Watt bulbs do the math and that will give wattage requirements.

More than just lights? Add whatever else coffe pot, microwave and so on. Most homes will not require the full wattage these Items may add up to because they will not or may not be used at the same time.

As for torque that is a question for someone else I will give you this advice, Wattage can be converted to HP and or torque. An example would be a 5,000 watt generator requires a minimum 10-Gasoline HP to operate at full load.

Sounds as if you are looking for an alternate power supply to run gen-set such as wind, water or human power. This can be difficult in most aplications where speed can not be controlled the power is generated as DC voltage and inverted? To AC. This allows more accurate voltage control.

You did not mention what form of heating you use, what size Fridge, do you want to run a electric or gas cook store, do you want to run a microwave,

Do you have gas or electric heat, is there electric blowers on a home.

On that 1800 sq ft home do are you running a hot tub ? Do you want every light on ?

I have a heat pump for example but for emergancy I would turn it off and use a natural gas back up heater in my home, I have a 10,000 watt generator that runs on high speed rpm at about that 3600 RPM.

I run my single door fridge, all my lights, TV VCR and a blower for the gas heater. ( I can even run the microwave as long as the fridge does not try to kick in) A fridge will have a much higher amp draw starting up, after it starts running it is lower amp. But you can unplug the fridge for a few hours and it stays cold if you need to run some other items.

I still own them, but my old back up system, used DC lights and things

We need to know some simple things.
1) What is your heating systems fuel? (propane, electric, etc... )
2) How many electrical appliances? Range, microwave, electric heat, heated floors, refrigerators, freezers?
3) Sump pumps?
4) Well pump?