We are looking into getting a backup generator for our house because we have a bad habit of losing electric fairly often. I have looked at the Generac unit, Briggs and Stratton, Kohler, Cummins, Kubota, and a few others. I am a little concerned with the cheaper propane units because it appears they are to be run for a short duration (24hr) and allowed to recoup, where as the diesel units can pretty much run from oil change to oil change without a break. (we have lost power up to 10 days before and a few days straight occurs about every other year at least). Any thoughts from the experts?
The other concern is the amount of power we need. We are 100% electric due to the fact we can't get gas where we live. (If I get a non diesel generator I would have to use propane to power it and have tank.) We are about 2000 sq ft, heat pump, electric backup heat (want to say 15kw strips), two fridges, freezer, 50gal hot water tank, then the normal lights, tv, etc.... (ok better add wife hair dryer and curling iron......) I am wondering if I can get away with a 21kw unit. Seems a lot of the diesel generators I looked at are 21kw, not seeing a lot of 25kw types. Now normally the heat pump would be working and not the strips in the furnace so my need would be far less - is this a concern? (wet stacking) BUT if the power was out when it is good and cold the heat strips would kick in and we would have a lot of demand so thus the possible need for a bigger unit, or so I am thinking? Anyone know can I limit the furnace to only half the heat strips on generator power or something like that?
May also look at adding a outdoor furnace in the next few years but I know the electrical need is low for them and that would help with the generator demand but for now that is just too costly for me to consider at the same time as a generator.
Any ideas and thoughts would be appreciated.
Ive installed 22 kw systems in houses similar to yours, but you have to lock out The heat strips when generator is operating. Generac utilizes wireless load shed modules to accomplish this. You can use up to 8 of these set with different addresses ( 1-8) depending on order of importance. If enough power is available it will allow operation.
I have a 22 kw unit operating my 4,000 sf house and it also supplies power to my barn. In my case, i got rid of old heat pump with electric heat strips and other electric appliances, and put in 98% efficient gas furnace, 95% efficient gas water heaters, gas range and gas dryer.
My generator ran a few weeks ago. Entire house ran incl ac. My hottub also continued to run the circ pump.
In your particular case, i put the figures into my calculator. I wasnt sure if you are on a well, but i threw that in. With the 15 kw heat strip youd be looking at a minimum 36 kw generator. Ive installed some 45kw units and your looking at some major investment. Like between 18-22 grand. And the fuel use is another factor. Your looking at between 8-9 GPH between these two units running at full output. Ive had clients that actually install larger units than they need simply because a larger unit will not have to run full out to operate their house, and actually use less fuel.
The other option is to replace your heat source and use smaller air cooled units. Ihave a current client that is yanking out old heat hump and electric strip heater (R12 unit) and installing modern heat pump with propane backup heat. This allows the use of 22 kw air cooled instead of 45 kw liquid cooled. It also gives them a modern heat system and generator for less money than the larger generator alone.
and as far as solar goes... you wouldnt believe the amount of generator calls i get from people living off grid needing generators up here. not enough sun. If i lived in Texas id use solar also. not where i live. Just doesnt work HERE.
And a last note about 3600 rpm vs 1800 rps. The 1800 rpm units are much quieter to say the least. If you want anything over 5,000 watts though at 1800 rpm, your probably looking at a liquid cooled unit as the engine has to be large enough to move the huge 4 pole alternator that produces the power. A 22 kw liquid cooled unit costs aprox 2x the cost of the air cooled unit. Install costs are the same, and surprisingly fuel consumption is approx the same. I chose not to install the liquid cooled version simply because i didnt see the net return from that investment as worth the difference FOR ME. i always manually shut down my generator at bed time. for me its a waste of fuel to run while i sleep. If its 20 below i may consider leaving it run, but it never gets that cold here. I heat with a wood stove, but use propane heat for backup. i also installed a 1,000 gal propane tank underground. I have clients that let theirs run 24/7 during outages, and there isnt any issue except to check oil and change oil after 200 run hours. If its 100F outdoors, i personally would cycle an air cooled unit off and on during the day so as not to overdo it in the heat. If i lived in a hot climate, i would have probability went with the liquid cooled option.
