# whole-house generator and fuel efficiency — need answer kinda fast **URL:** \ **Category:** Factual Questions\ **Created:** [September 8, 2017, 9:35pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846 "2017-09-08T21:35:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Cayuga](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Cayuga](https://boards.straightdope.com/u/Cayuga)\ **Post date:** [September 8, 2017, 9:35pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/1 "2017-09-08T21:35:21Z")
A whole-house generator burns gasoline and produces electricity. Is the rate at which it burns through the gas affected by how much electricity is used? In other words, if one has lost power and it may be several days or a week before they can get more gasoline, should they reduce the amount of electrical devices they use? Or does the generator burn fuel at a constant rate no matter how much electricity is drawn? ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [September 8, 2017, 9:39pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/2 "2017-09-08T21:39:56Z")
My generator burns propane, not gasoline, and I don’t notice any difference in the sound the engine makes dependent on how much load I am using at that time, so I’m guessing it’s doesn’t matter what the load is since the generator is putting out the max power it can all the time. Now someone will come along and say I am dead wrong… ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 8, 2017, 9:48pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/3 "2017-09-08T21:48:28Z")
You’ll burn more gas with a greater load. But as above, you’ll probably be close to the max for the generator anyway and not notice much difference. ---
**Author:** ![KCB615](https://avatars.discourse-cdn.com/v4/letter/k/ea666f/32.png) [@KCB615](https://boards.straightdope.com/u/KCB615)\ **Post date:** [September 8, 2017, 10:25pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/4 "2017-09-08T22:25:00Z")
The manual for my natural gas powered generator says the following on fuel consumption : Natural Gas: Half load - 148 cubic feet/hr Full load - 240 cubic feet/hr LP / Propane: Half load - 63.2 cubic feet / hr Full load - 102 cubic feet / hr I would expect a gasoline powered generator to be similar, half load is a little more than half the fuel consumption of full load. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [September 8, 2017, 10:35pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/5 "2017-09-08T22:35:13Z")
More load = more fuel (conservation of energy and all), same with the car alternator (people think they just take a continuous load, not based on the electrical demands). I have a gas generator and when a heavy load, like the well pump, or A/C kicks in you can really here it strain and rev back up. As for the above post, no the generator is not putting out max power all the time, it is putting out the power required to meet the demand. It actually can not put out more power then the demand, as that would simply cause the generator to spin faster as there is more power then load, then that would trigger a lowering of throttle to bring the RPM’s back within range needed to maintain about 60 htz. ---
**Author:** ![JHBoom](https://avatars.discourse-cdn.com/v4/letter/j/13edae/32.png) [@JHBoom](https://boards.straightdope.com/u/JHBoom)\ **Post date:** [September 8, 2017, 10:47pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/6 "2017-09-08T22:47:48Z")
> [@Cayuga](#): > > A whole-house generator burns gasoline and produces electricity. **Is the rate at which it burns through the gas affected by how much electricity is used?** Yes. > [@](#): > > In other words, **if one has lost power and it may be several days or a week before they can get more gasoline, should they reduce the amount of electrical devices they use?** Or does the generator burn fuel at a constant rate no matter how much electricity is drawn? Yes. The best way to conserve a limited fuel supply is to not run the generator full-time. ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [September 8, 2017, 10:50pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/7 "2017-09-08T22:50:10Z")
Mine is also natural gas powered and it definitely uses more fuel at higher demands. Generators use a lot of fuel, they are very inefficient compared to the utilities. A gasoline powered one will be challenging to keep fueled during a gasoline shortage. Best bet may be to only run it when you need it if you can do so. A refrigerator or freezer only needs to run every so often, for example. Don’t try and maintain your normal lifestyle of lights all over, A/C running constantly, TVs on, etc. if fuel is in short supply. I have a 6500 watt unit and it powers everything I need, even the A/C, but I can’t run everything at once. Dennis ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [September 8, 2017, 11:05pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/8 "2017-09-08T23:05:46Z")
> [@KCB615](#): > > The manual for my natural gas powered generator says the following on fuel consumption : > > Natural Gas: > Half load - 148 cubic feet/hr > Full load - 240 cubic feet/hr > > LP / Propane: > Half load - 63.2 cubic feet / hr > Full load - 102 cubic feet / hr > > I would expect a gasoline powered generator to be similar, half load is a little more than half the fuel consumption of full load. So for a propane system each hour at full load uses 3 gallons of propane? how many KW is your system? ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [September 8, 2017, 11:22pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/9 "2017-09-08T23:22:11Z")
> [@Cayuga](#): > > Or does the generator burn fuel at a constant rate no matter how much electricity is drawn? I’ve been trying to come up with some scheme by which this could possibly be true. The best I can think of is a generator that has some electricity-wasting attachment (say, a large heater element) where it can dump excess current when the real load is less than max. The question is sort of like asking “Can you run (on level ground) at 10 mph, expending the same amount of energy as you would at 5mph?” ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [September 8, 2017, 11:32pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/10 "2017-09-08T23:32:56Z")
> [@dolphinboy](#): > > My generator burns propane, not gasoline, and I don’t notice any difference in the sound the engine makes dependent on how much load I am using at that time, so I’m guessing it’s doesn’t matter what the load is since the generator is putting out the max power it can all the time. Now someone will come along and say I am dead wrong… you’re not _dead_ wrong, but… you don’t notice much different in sound because your generator has to run at a constant speed to maintain 60 Hz alternating current\*. it’s not making max power all of the time, the governor simply keeps the engine at the correct RPM all of the time to ensure the AC waveform is 60 Hz. as you add more and more load (draw more electrical power from the generator) the governor will open the throttle more and more (thus also consuming more fuel) in order to keep the engine at the correct RPM. - assuming you don’t have an “inverter” generator which generates DC then uses electronics to convert it into an AC waveform. I don’t know if too many whole-house generators are inverters. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [September 8, 2017, 11:37pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/11 "2017-09-08T23:37:18Z")
Do you use more gas driving 70 mph compared to 35? You get the same result with any engine. It uses more fuel when it’s worked harder. My whole house generator sounds much, much different when my Central Air kicks on. It’s really chugging. I sized it to carry that electrical load. I’ve started shoving the thermostat up when I need to use my oven. I’m afraid it might trip the breaker. I originally had a 1800 Watt portable than ran my fridge, a few lights, and TV. It chugged down (the governor kicking in) when I used my 2 burner hot plate. Fuel consumption is what drove me to switch to a natural gas whole house. My portable required refueling every 4 1/2 hours. It drove me nuts over a six day power outage. Kept running out of gas and I had to drive to the service station. Twice! Generators eat fuel. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [September 8, 2017, 11:45pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/12 "2017-09-08T23:45:57Z")
I wouldn’t worry about small items. Turning on the TV, DVD player, or a table lamp. That’s not enough to noticably effect your fuel consumption. Electric Dryer, Oven, some of the bigger Fridges require more power and that means more fuel. I switched to a Gas dryer three years ago. I eventually will get a gas range. But for now the whole house generator handles it fine. I only worry about the oven when there’s a chance the AC might cycle on. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [September 8, 2017, 11:56pm UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/13 "2017-09-08T23:56:36Z")
Oh, I almost forgot. My Honda portable had a fuel efficiency setting. I always kept that switch on. It ran faster with that switch off and used more fuel. The trade off is the generator had to noticably run faster under load. That Honda hated my coffee pot. The governor kicked in and it ran much faster until the coffee pot turned off. Too bad. I need my coffee every morning. 😃 The Honda got sold and is at a deer camp now. ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [September 9, 2017, 2:59am UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/14 "2017-09-09T02:59:29Z")
Inverter generators are drastically more efficient. They aren’t “whole house”, though. You could do “fridge and a mini split and the electronics”, but not start your main A/C or oven or anything. Inverter generators consume 1-2 gallons per 12 hours, generally, though it depends on load, like everything. They also make inverter generators you can run on propane, which is handy because you can have a propane tank stored long term, while you can’t really store gasoline. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [September 9, 2017, 3:24am UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/15 "2017-09-09T03:24:57Z")
> [@Wesley\_Clark](#): > > So for a propane system each hour at full load uses 3 gallons of propane? how many KW is your system? That would be in the 12 to 14 KW range. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [September 9, 2017, 3:30am UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/16 "2017-09-09T03:30:47Z")
Another thing to keep in mind is that there is some optimal load at which the generator is most efficient (i.e. less wasted gasoline that doesn’t get turned into usable electricity), and “minimal” isn’t it. If there are some low-power devices you can take off the generator and only run it for the high-draw devices once in a while (refrigerator, hair dryer, clotheswasher, etc.) and put the rest on a battery bank, even better. For example, if you have a few USB power banks for cell phone charging and small LED task lights, you might not need the generator on some nights at all. For example, if you were running the generator on 10% capacity, it may be wasting an additional 10% just on efficiency that you might’ve otherwise been able to harness for usable power, even if it’s just dumping it into a car battery or some such. If you have the time (a week or two?) it might be worth investigating small backup batteries for this purpose, so that you run the generator full load to charge the battery, and then use the battery to power whatever else you need to. If it’s imminent (hurricane?) don’t worry about it, just stock up on gasoline. And/or rush-order some portable solar panels… nothing under 20W; they’re useless. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [September 9, 2017, 3:51am UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/17 "2017-09-09T03:51:48Z")
> [@dolphinboy](#): > > \ I don’t notice any difference in the sound the engine makes dependent on how much load I am using at that time, so I’m guessing it’s doesn’t matter what the load is since the generator is putting out the max power it can all the time. Now someone will come along and say I am dead wrong… Become _ **one** _ with the machine.🙂 Listen to the difference in the sound it makes while idling with no load @ 3600 RPM and the sound it makes struggling to maintain 3600 RPM @ full load. It is **very noticeable** if you pay attention. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [September 9, 2017, 3:59am UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/18 "2017-09-09T03:59:22Z")
> [@Reply](#): > > Another thing to keep in mind is that there is some optimal load at which the generator is most efficient (i.e. less wasted gasoline that doesn’t get turned into usable electricity), and “minimal” isn’t it. If there are some low-power devices you can take off the generator and only run it for the high-draw devices once in a while (refrigerator, hair dryer, clotheswasher, etc.) and put the rest on a battery bank, even better. For example, if you have a few USB power banks for cell phone charging and small LED task lights, you might not need the generator on some nights at all. > > For example, if you were running the generator on 10% capacity, it may be wasting an additional 10% just on efficiency that you might’ve otherwise been able to harness for usable power, even if it’s just dumping it into a car battery or some such. If you have the time (a week or two?) it might be worth investigating small backup batteries for this purpose, so that you run the generator full load to charge the battery, and then use the battery to power whatever else you need to. If it’s imminent (hurricane?) don’t worry about it, just stock up on gasoline. And/or rush-order some portable solar panels… nothing under 20W; they’re useless. It still takes energy (from the generator) to charge the batteries, no? ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [September 9, 2017, 6:00am UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/19 "2017-09-09T06:00:43Z")
> [@Xema](#): > > I’ve been trying to come up with some scheme by which this could possibly be true. The best I can think of is a generator that has some electricity-wasting attachment (say, a large heater element) where it can dump excess current when the real load is less than max. > > The question is sort of like asking “Can you run (on level ground) at 10 mph, expending the same amount of energy as you would at 5mph?” Yes you can, if you have an older electric golf cart. And they do it just like you postulated, There is a bank of resistors under the cart, usually 3 of them connected in series. For 1st speed all of the coils are in the circuit. 2nd speed bypasses the first coil, and so forth until you get to full throttle which connects the battery pack directly to the motor. The old operator’s manuals would mention to accelerate smoothly to top speed and stay there for most economy. In the 1980s solid circuit controllers entered the market. And boy do the old resistors run hot! They moved them up higher since you could set fire to tall grass when the cart was parked. I have a door in the back and can observe the coils, they are red hot in low speed. [http://www.golfcarcatalog.com/golf-cart-blog/golf-cart-speed-switches/](http://www.golfcarcatalog.com/golf-cart-blog/golf-cart-speed-switches/) Dennis ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [September 9, 2017, 6:23am UTC](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846/20 "2017-09-09T06:23:23Z")
This is in context of **draining** an **existing** battery bank… Right? Nothing to do with _charging_ it per Xema"s post :smack:??? [Next page](https://boards.straightdope.com/t/whole-house-generator-and-fuel-efficiency-need-answer-kinda-fast/795846.md?page=2)