Sizing a genset?

[llong66]

Ive decided on getting either a MEP-002A or MEP-003A, the problem is I am not sure which one would best suit my needs. I am wanting something to power the whole house, I do not need to worry about the furnace or water heater as they are gas and in any longterm grid outage I will need to use other sources for this. While looking over my electric bill for the last year, I have avg about 700kwh/mont with figures out to 23.7kwh/day or a lil under 1kwhr/hr. Would a 002 be enough for me? I know there are peaks in usage, but if I am thinking right, I would be ok w 5kw. The price diff between the units is not that much, its the fuel consumption I am mainly looking at. Thanks for your help!

Greg

 

[Jimc]

Well an 003 at 1/2 load is a hair over 1/2 gal hr. its my understanding an 002 at full load is a little over 1/2 gal hr. per kw it seems fuel usage between the two is fairly close. I chose an 003 myself so it would run my air and everything im the house. 002s seem more avail though around here anyway. 003s seem harder to find.

 

[jbk]

get both

 

[richingalveston]

to size your genset, your electric bill has little to do with it. you need to determine your full load amps you wish to power. you need to know how many amps your AC, fridge and any other appliances draw at full load that you want to power. You can shed the load by not using some things but you need a much larger generator to use as a whole house unit than you would think unless you can really limit what is used at one time. a 5kw will probably not run your hvac if you have central air. If you have a clamp meter then you can turn on what you want to be able to power, clamp your incoming power and get the total amp draw. You then need a generator that can handle the total amps you need to power at one time. you must caclulate your peak amperage and size the generator for this or you will continually trip the genset breaker.

 

[johnray13]

It's a hard question to answer without knowing a lot of specifics. Motor starting loads are probably the biggest consideration. Just a few everyday items can quickly use up the extra power you need to start well pumps and motors. For example, a microwave along with your coffee pot and a hair dryer with a few lights on your close to 4000 watts. If my well pump kicks on I would pretty much max out.

Like Jim said, the fuel usage is pretty close, so having the extra 5k watts gives me a little more breathing room. I went with the 003A 'cause 5k seemed too tight for me.

John

 

[Isaac-1]

You don't tell us much about your situation so it is hard to give specific answers, so instead I will say a few general things:

In a power outage any generator beats no generator

If a generator is not needed for climate control (electric heat, or if your in an area situation where air conditioning could be considered life support), and there is no special need like ability to run a well pump, etc. then most people can survive somewhat comfortably of a 3-5KW generator if they are willing to do some manual load balancing. Also thanks to modern CF and LED lighting it is now possible to at least minimally light most of a typical home on the amount of power that was used with just 2 or 3 traditional 75 - 100 watt incandescent bulbs, much the same can be said about many other modern conveniences, newer flat panel LED lit TV's typically consume less than 50-60 watts of power for screen sizes under about 42 inches, notebook computers rarely draw over 100 watts, etc. Even the big power hogs like refrigerators and freezers draw only a fraction of the power they did 10-20 years ago. As a result it is possible to power essential loads (fridge, freezer, some lights, maybe a tv or radio all at once) with something as small as a 2KW generator, and with a little load management you can even power a microwave oven, or a toaster for short periods by temporarily unplugging those larger loads mentioned above. The real need for larger generators comes in if your not willing to do this sort of load management, or if you must run a larger all electric appliance (water heater, well pump, etc)

 

[jamawieb]

Isaac-1 explained it perfect.
I'll tell you my situation and maybe it will help:
1500 sq ft home, chest freezer, refrigrator, normal home electronics, central air/heat but stove, water heater and furnance operate off propane. I purchased a mep-002 and it runs the entire house (every light, electronic, 2 space heaters, etc.) fine. The only thing I can't do is run the clothes dryer and central air at the sametime, so I just divide the load between using the two items. FYI: It's better to run military generators at full capacity, then it is to just have them running on a minimal load.

 

[steelypip]

Jamawieb makes the point that I would: it's better to have to shed some load to keep from overloading the set than it is to have the generator spending most/all its time at 10% or less load. We just had a two day outage and at no point did I wish for more power than our MEP-002A can make. Ours will run lights, small appliances and both heat pumps (upstairs and downstairs) or one heat pump and one other 'big' appliance along (dryer, cooktop, microwave) with all the small appliances. That's all I need or want. And yes, the fuel consumption is less than the 003A - compare the size of the day tanks, which are sized for 12 hour runtime.

 

[quickfarms]

The electric bill has nothing to do with sizing a generator. You need to figure you loads. During an outage you do not need to run the generator 24 hours a day. 6 to 8 hour is sufficient to keep the fridge and freezer cold. You typically run the generator from dusk to bed time. I have worked and stayed at some remote locations and the generators were shut down at a specific time at night and would be restarted the next day.

 

[steelypip]

The electric bill has nothing to do with sizing a generator. You need to figure you loads. During an outage you do not need to run the generator 24 hours a day. 6 to 8 hour is sufficient to keep the fridge and freezer cold. You typically run the generator from dusk to bed time. I have worked and stayed at some remote locations and the generators were shut down at a specific time at night and would be restarted the next day.

Quoted for truth - unless it's above 80 F at night, you're just not going to want to run the (expensive, loud) generator all night.

I have a (very) little generator (Sawafuji "Onan" K450) which is just big enough to charge batteries, run a few lights, and run the wood heater blower. The 1/2 gallon tank gives 6 hours of runtime. That's how little it is. I might upgrade to an inverter generator like an EX1000 Honda for this job. That's the generator that runs overnight to blow the warm air around from the wood heater. If I'm at home during the day, it generally is all that is running until about 2 PM.

When we decide it's time to cool the fridges back down, charge batteries, etc, then I start the MEP-002A and do the PM on the little generator during that time. If I'm gone during the day, I start the MEP-002A in the morning when I leave so that the family have whatever they need. Likewise, when the Dorado came through and we had 95 F temps and no power, the MEP-002A ran from 10 AM to about 8 PM daily to keep the heat pump and fridges running.

You care about fuel consumption not primarily because of cost but because of availability. If a hurricane blows through (I was in metro Raleigh when Fran toured the area), gas stations may have no power for days, or conditions on the roads can be so bad (30" oak trees across the road, floods, precip) that you can't get to one. When we had the 'big snow' three years ago here, I couldn't get a vehicle up the road to my driveway. I carried every gallon of fuel we burned about 150 feet uphill and a quarter mile of distance (five gallon Kerosene totes with the handle on top) for three days.

I'm better equipped for this kind of situation now, but schlepping less fuel up the hill is definitely a factor in my disaster preparations.

 

[edgephoto]

You certainly want the smallest genset that will do the job. Fuel is the problem.

For me during an outage I really do not care about the cost. It is a short term expense. However the issue is locating or having a supply. October 2011 I lost power for 7 days. I have a gasoline portable genny that does the job. It used an average of 1/2 gallon per hor during the 7 days. My problem was I had just purchased it so I only had about 3 gallons of fuel on hand. Trees were down some roads were completely impassable. Power was out all over. I found a hardware store that was open but in the dark. Bought the last 2 5 gallon fuel cans he had. Then I drove for almost 2 hours in a search for fuel. When I found it the line was hundreds of cars deep. Luckily since my car was near full I just walked to the pumps and was able to fill my cans without waiting in the car line. Also I had cash. The internet was out so no cards could be processed.

After the storm I bought 4 mil surplus jerry cans and I keep 20 gallons in those cans and rotate it every 6 months to keep it fresh. That plus my 5 gallon lawn mower can gives me 50 hrs of "normal" generator use. I ran mine from morning 7-8am until about 10 PM.

The long term outage possibility seems much greater nowadays. So the whole fuel storage thing got me thinking diesel. I have home heating oil in my basement for my furnace. Since portable diesel generators are quite expensive unless you get a Chinese no name junk model I decided one of these military units is perfect. They are reasonably priced, durable and weigh enough I have no fear of theft. Once I permanently install mine behind the garage I will just use a cord to connect to my generator connector if I need it. I am toying with either keeping a drum of fuel near the genny or some 25-30 gallon storage tank nearby. Then I can go 100 hrs or longer on my fuel supply. And if treated and stored properly the fuel is good for years. I am also going to make a setup to pump fuel out of my oil tank. This way in case of a really long term outage I can have power and heat.

I do not want to deal with the hassle I had finding fuel. I also do not like having to worry about rotating out my fuel etc. I have thought about an MEP-003a instead of the 002. However they use roughly twice the fuel. I rather do some load management and have a longer outage capability.

 

[steelypip]

You certainly want the smallest genset that will do the job. Fuel is the problem.
...

The long term outage possibility seems much greater nowadays. So the whole fuel storage thing got me thinking diesel. I have home heating oil in my basement for my furnace. ... This way in case of a really long term outage I can have power and heat.

I do not want to deal with the hassle I had finding fuel. I also do not like having to worry about rotating out my fuel etc. I have thought about an MEP-003a instead of the 002. However they use roughly twice the fuel. I rather do some load management and have a longer outage capability.

I clipped some stuff out of your post for emphasis. My doctor neighbors went with turnkey autostart LPG Generac systems and buried LPG tanks...which would make sense, except that only one of them has bothered to put in so much as a gas stove. The other uses the LPG only for running the generator which, sadly, gets run about five full days per year.

We don't have LPG (yet - thinking about a gas cookstove). The deciding factors for me that led to diesel fuel over LPG for the generator were 1) availability, 2) liquid at normal pressure means I can transport and store it in jerry cans, kero cans, cubies, or even contractor buckets. The propane truck doesn't make it up our hill very well when the pavement is clean, dry and tree-free. I can't guarantee that we wouldn't run through the tankful of propane before the truck made it up the hill, and a grill bottle wouldn't really get me very much runtime (lower energy density per gallon). and 3) ability to blend my own fuel out of gasoline and WMO in a pinch. I always seem to have a bunch of WMO laying around, and I've always got at least 20 gallons of gasoline around in cars, if nothing else. In an extended crisis I could blend and filter quite a bit of fuel if necessary to make some kilowatts to keep the freezers frozen, and could get a whole lot of runtime for the little generator. Can't do that with an LPG generator either.

If you have home heating oil or something else running on diesel fuel around, then a diesel generator is really the only kind that makes sense.

Long term outages are something we've brought upon ourselves with the 'deregulated utilities' nonsense. Why anybody thought deregulating a private monopoly was a good idea I'll never know - the "invisible hand of the free market" only works when there IS a free market, which there emphatically isn't where your single power utility is concerned. My father-in-law worked in the power business for many years. He often spoke of how the utilities quit stocking so many spares and keeping so much repair staff and equipment around the instant they were not required to by the regulators (primarily FERC).

As it is, our power goes out for more than a day an average of four days per year with a standard deviation of about another four days per year. Thanks Dom.com - you really live up to your name. It's not a whole lot better than living in Pakistan, where at least they tell you the schedule when the power will be off...

 

[Isaac-1]

Another follow up to that last message about fuel of choice, a lot depends on the type of outage you may expect, localized or wide spread, length of outage, etc. Around here it is mostly hurricanes which can cause wide spread long term systematic outages, for example when Rita came through in 2005 my inlaws had an order in to have their then low propane tank refilled, delivery ended up being on a Sunday 3 weeks after the storm, and they were lucky to get it.

 

[steelypip]

The whole point of this sort of disaster management planning is that you can't really predict what the next disaster will be, nor when it will be, nor what the worst one you'll experience will be. That said, you can play the odds and make worthwhile compromises.

In my case, I live on top of a hill about 100 ft above the water table. Flooding, other than a little water in the basement, is not going to happen in anything less than a biblical scenario. So I don't have to worry about my personal version of a Fukushima. What I do have to worry about is mature red oak trees and a fair number of pine trees around a narrow, twisty road and driveway (with power line on poles along side) climbing aforementioned hill and a power utility focused on profits rather than quality of service. I'm zoned rural and within 5 miles of the city limits of a city with about 50,000 people in it. They have the same power utility problems I do, but they tend to get their power back 1-3 days sooner. We have no municipal water, sewer, or natural gas, although the city does.

We're not really in hurricane territory, but one has blown through in living memory. I'm quite sure that my road would be closed for 1-2 days after a hurricane passed through, and power would be out at my house for at least five days in that scenario (it was out for 4+ after the big snows of winter '08-09) Accordingly, I've got to keep everything going on internal stores for a minimum of 3 days and a likely maximum of seven days. That's what drives the fuel, food and water planning. After three days my neighbors (or the county) could have cleared the road adequately and I could probably get the driveway passable regardless of what fell across it. At that point, I can get to the city to get more generator fuel, typically on about day three. If the roads still aren't open I should be able to take the kerosene cans, chain saw, and quad and get to some #2 diesel somewhere.

As a matter of practice, we keep rather more than seven days worth of food around. Water, while not hard to find, gets more difficult to get to the house after about day five (common well down at the bottom of my hill). I always have at least 24 hours of runtime of diesel fuel for the MEP-002A, and a lot more than that of gasoline for the small generator. I have a gallon of white gas for the camp stove. There are plenty of candles and flashlight batteries. And we get to 'test' all this once or twice a year for days at a time.

That's the kind of planning you do. If we lived on the coast or in a city in a tidal plain it would be a different decision set. I would, however, be cautious about depending for days upon resources not on site. Municipal gas is wonderful generator fuel until the accumulator tank runs out or the pipeline stops delivering...