generator set for whole house

Got an 1800 sq ft house with 4 ton a/c, electric range, washer, dryer, microwave and various low draw lights, etc.
What is a good kw number for a "whole house" generator that will, for sure, run the lights and a/c, at least? I'm thinking 15kw would do it, once stuff was online. I'm told to go from the biggest load to the smallest in bringing stuff online.
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RB wrote:

What's the SEER of the A/C? Divide 48000 by the SEER and it will give you the steady state current requirements in watts.
Note that starting surge for A/C systems can be six times or more the running load. A "hard start" kit will reduce the starting current requirements, so if capacity is a problem then have a hard start kit installed. Don't forget that once the thermostat is satisifed and the A/C shuts off you'll still have all the rest of the load there....and the A/C may not restart unless you shed that load first.
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What is a hard start kit? A google search showed many for sale, but no explanation of what they are.
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toller wrote:

It is a large non-polarized electrolytic capacitor along with a time delay relay, designed to provide an additional current source during the compressor start phase.
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Your probably going to need a 15kw just to get the a/c started. 15000 watts translates into 62.5 amps.
Musing about
A/C 20 amps running, starting 120 amps, better part of a second at least Oven 40 amps Water heater 25 amps Washer 20 amps Dryer 30 amps
these figures might be a little on the high side except for the washer. When washers go into spin mode they will draw upwards of 18 amps, at least mine will. Your compressor will have a LRA number this can also be used as the starting amps.
There are a ton of variables, some interlocks will help. Make sure that the generator you choose is rated for 100% loading. Most stand-by units are 80% of full load. Then comes the fuel issue.
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Not if you want to run the AC! Better consider about 25kw. Greg
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