Cost of Home-Generated Electricity

What is the cost of electricty created using your own at-home generator?

I have a 5KW generator for backup during storms, but I’m wondering how it compares cost-wise to what I get from the elctric company.

Around here they figure the electric company is about 11 cents per kilowatt hour.

Ignoring the cost of the generator itself (since I already have it) if I put gas in at let’s say $2.70/gal and just run it for hours, what cost-per-kwh am I likely to encounter?

On the few occasions I have run it it seems to go a long time on little fuel. But maybe its not drawing a full 5 KW either. Still, if a gallon of gas lasted 5 hours at 5KW I’d be in the ballpark of 11 cents/kwh.

I know I could just do an experiment but that’s noisy and I have neighbors, some cranky.

Those generators are not designed for long term use. It would not be safe, IMV.

I have some experience with permanent generators that run on natural gas, or liquid propane.

Even those generators are designed for short term use and I can tell you that they are much, much, much more expensive than utility power.

I can’t imagine that gasoline would be much better.

And can you really run an entire house on a 5KW generator? I live in the mountains, have a 3,500 sf house with a ground source heat pump, and have a 12KW emergency generator and I can only run about 50% of my house off of it. It runs on propane and I really doubt I can run it for less than the 7 cents a KWH that I am paying my electric provider… even if it was designed to run all the time… which it isn’t.

I did a rough calculation and IIRC it was about 10x as expensive in fuel alone then grid power. Besides the generator, there is the issue of unstable power supply, any load will produce a voltage drop till the generator gets back to speed, and the over speed condition as well - which will wear on the devices running off of it, though some generators use a battery to help out there. Your generator will most likely be operating at a inefficient range, esp at low loads, which wastes gas.

You may have a better shot if you can sell unused power back to the utility, this way you can operate near peak efficiency, but I still think you will fall short.

Yes, I can run a 2400 sf house off of a 5.5kWh without any noticeable restrictions, even a 15,000 btu a/c included and a very deep 220V water pump. Dryer and cooking and hot water is propane, heat is oil. At one time the dryer was electric and that I could not run.

Wiki says 87 octane gas has 32 MJ per liter of power, so thats 8.88 KWH per liter.

1 gallon has 3.785 liters in it, so thats 33.61 KWH per gallon.

So right there, you will be paying 8 cents per KWH, assuming $2.70 a gallon for gas.

Unfortunately, ICEs are nowhere near 100% efficient, with the absolute best being 50%… Which a little generator you bought at home depot has no chance of matching, so lets just guess 35% efficiency.

Which brings the total cost of power to $0.23 per KWH.

Stick to the power companies. They know their business. Even the best setup will still have you paying double what the power companies can provide(since they don’t use expensive fuels like gasoline or diesel), and this still hasn’t accounted for the increased maintenance costs, which is already figured into the power company prices.

As others have said, you’re not going to beat the power company on conversion efficiency or fuel price. A gasoline engine is going to give you about 25% conversion efficiency at best, somewhat more for a diesel, whereas the power station gets at least 30% and possibly up to around 50%.

The one place you can beat the power company is where the waste heat ends up. If you’re living somewhere cold, you could arrange things so your generator’s waste heat is providing space heating and giving you hot water. Imagine a water-cooled diesel engine generator with the radiator inside the house and a second heat-exchanger taking the heat out of the exhaust and you get the idea. The power company sends its waste heat up the cooling towers, or into the sea or a nearby river. If you’re already using fuel oil for heat, you can burn it in a diesel generator anyway.

The concept is called combined-heat-and-power, and in cold areas you can use 80-90% of the total energy in fuel going to a generator. But it takes a bit more technology than goes into your standard emergency generator.

I wasn’t seriously considering doing it. I was just curious as to how near the current electric rate the things were. I can think of a half dozen reasons why, even if it were a little less than the electric rate, it would be a bad decision.

The interesting thing, to me anyhow, is my cost would be pretty much based on fuel alone, wheras the cost structure for the electric company has on one hand a lot more overhead, and on the other hand the benefit of volume production.

There is a second one: transmission loss.
Between 5-10% of the electricity generated at the power plant is lost in transmitting it over the power grid to your home. For your own generator located alongside your house, such losses are minimal.

Here in this little po-dunky town in Oklahoma, we just recently went through an ice-storm that caused 12 consecutive days of zero electric availability (from downed lines/poles/etc). After Day Two, I went and bought a 5Kw generator that had a four gallon tank - and required refilling every 5 or 6 hours (at best). And it was LOUD. Every other house in town had gens running and with little other ‘background noises’ around, the whole town was throbbing 24/7. HUGE headaches, especially since there were only two places to purchase gasoline and often they were awaiting more fuel themselves to power their generators. Not to mention fallen trees on roads making it necessary to walk to store(s) lugging 10-15 gallons of gasoline at a time.

Anyways, my point is that there is NO way I could have maintained much longer (from a cash standpoint) in providing basic electric for my near-blind wife. It was costing probably around $40 or $50/day, and even more when I was asked to fire up the other generator (lent to me) for power above and beyond what the first one could give. The whole scenario was ridiculous with how long it took to get FEMA’s ‘megawatt’ generators online to this power-grid. I smiled hugely when I saw the trucks with the gens upon the trailers, but a two-day delay in getting the friggin’ correct pieces to hook 'em up (so I heard later) made the frustration so much more palpable in the din.

‘Commercial electric’ is much, much, much cheaper (and safer too!) overall when its all said and done, IMHO. I don’t even remember how many times I had to change the oil in those gens at ~$6/quart (synthetic, of course!). Ugh…

A 5 kW generator would be enough to run some but not all of the electrical loads in a typical house. In Ireland a normal domestic supply is rated to 63 A at 230 V which is 14.5 kW. If you turned on the immersion heater (domestic hot water) (3000 W), the oven (1500 W) and the shower (2200 W) at the same time you would exceed the output of a 5 kW generator, and that’s with no lights, fridge, entertainment, etc. Even small appliances like electric kettles and toasters use kilowatts. So if you’re running your house on a small generator I guess you just have to be smart about which appliances you run simultaneously, and adopt a much more frugal attitude than when you are on a mains supply.

What kind of crazy showers do you have in Ireland that use 2200W of power? Around here the waer from our shower is fed from the water heater (which can be electric, but mine is gas).

My biggest concern with a couple of kids in the house was being able to run the furnace blower (gas furnace) or some room air conditioning units, the fridge/freezer, and a few other things to keep us distracted a bit, like a TV.

My oven, water heater, dryer, cooktop, and furnace are all gas, and that was one of the considerations in choosing gas over electric. We very rarely lose gas.

[quote=“crazyjoe, post:12, topic:534650”]

What kind of crazy showers do you have in Ireland that use 2200W of power?


Probably an on demand water heater. Heats the water as you use it. Those suckers draw some power.

[quote=“billfish678, post:13, topic:534650”]

[quote=“crazyjoe, post:12, topic:534650”]

What kind of crazy showers do you have in Ireland that use 2200W of power?

2200W is nothing for a water heater.
Most US heaters use elements that are 5500W.

In the UK (and I’m guessing Ireland too) water pressure in household pipes is much lower, so in a lot of homes (particularly older ones) you need a two-pump powered shower to get anything useful out of the shower head.

A 5000 watt generator will be 20 amps at 240V and 43 amps at 115V.

Most houses have at least 100 amp panels.

You could run the house but you’d have to be mighty careful, and other than a small A/C and refrigerator you wouldn’t have much left.

A [electric] stove, dryer, freezer central A/C etc would be out of the question.

In 2002 my household was without power for 14 days due to an ice storm. On the second day, I bought a 5K generator. It generated enough power to run the fan on our gas heater, the refrigerator, a few lamps, an electric skillet for cooking, a TV with satellite dish and one computer.

It would take nearly 15 gallons of gasoline per day to run 24 hours. At the time I believe gas was at about $2.00 per gallon because it seemed to cost about $30 per day.

Our rural electric cooperative had to double their rates to pay for an almost complete replacement of their plant due to the ice storm. Even afte doubling the rate, I never complain about the electric bill because of this experience.

(slight off topic drift here) Kingfisher, I’d bet heavily that you and I shared very similar experiences in the ice-storm stuff (you’re north of OKC, correct???). Fortunately, the '02 storm left the area’s electric grid where I lived at that time more or less intact, but my full sympathy to ya for what you/others (if I assume correctly) went through. Since about a month ago, I, too, look at electric rates with a different opinion. Running what seemed like miles of industrial-strength electric cords through the house (no good way to isolate outside grid with absolute safety) and keeping loads ‘balanced’ is darn near a full-time endeavor. Its hard for most folks to fully realize what a tearfully beautiful sight it is seeing long-dark streetlights flickering off/on unexpectedly as the ‘commercial-grid’ was re-energized. It meant that the cost of modern-living was about to go waaaaaay down (finally).

It makes a very interesting story (of numerous aspects) of how much things change when those wall plugs are useless, 'eh?

If you really want to go off-grid, at a minimum you will require a large battery bank (figure around $2,400 for this), a good sine-wave inverter putting out at least 5,000 watts (and if you really want to emulate grid power, you will need two of these to put out a total of 10,000 watts) costing about $7,000 for the two, a good diesel generator of at least 6KW, at $6,000, and a large solar panel array of at least six panels costing $400 each. Total this all up, and you end up at almost $18,000 to get started. Then add another $2K for miscellaneous (gages, control panels, cabling, etc.) and you are right at $20,000. The cost of sunlight is free after you buy the panels, but the generator burning a pint an hour of diesel, will cost around $0.40 an hour to run. If you really want to get fancy you can add a wind generator into the mix. I have a cabin on an isolated island with no grid power, and I know folks that have all of this in one system.

And this system won’t last forever. The batteries will need to be replaced at around 10-12 years, the inverter after about 15 to 20, depending on location, and the solar panels at around 25 years. The generator should go for 12,000 hours without rebuilding.

The above is expensive and quite a bit of hassle, but if you like gadgetry, gages, and that sort of stuff it is a lot of fun. And power outages will be a thing of the past.

I find the best source of information for all this is at Backwoods Solar, located in Idaho. Their web site is

A refrigerator is under 500 watts steady state while cooling, though starting current is much higher. Generators typically have reserve power and can go about the rated power output for short times, and the breakers allow a slight time lag for these overages. The AC cools 1/2 of the 2400 sqft, so it’s not a small unit, again no problems. I never had to watch what I used when running the generator.

Yes electric heat/appliances would have caused a much bigger demand

Looking at the generator it is 5.25Kw (not 5.5) but with a 6.5 Kw surge, which allows for the higher demand of the fridge, a/c and waterpump without tripping the breaker.