Step 1

Make a Checklist of Electrical Devices & Apliances you will need to run

The first thing you need to do is to decide what you need to power when the power is out. This will rank depending on personal preference and situation but usually ranks like this.

Lights>Refrigeration>Cooking>Entertainment>Heat>Cleaning.

Remember cooking and heating equipment takes ALLOT more energy than anything else in your home. If you must power those appliances (if the power is of for an extended amount of time) you can perhaps power only those appliances or get a generator able to power all of your equipment at the same time.

Step 2

Learn how much power each device draws and add it all up.

Once you have identified the appliances you need the next phase comes into play.

When you are sure on what you need to power the next goal is to identify how much power each appliance draws. In the article below there is a comprehensive list that shows the average power requirement of common household appliances. Write down each appliance usage (this is a number indicated by watts) and add it all up to final figure. 

If a certain appliance that you need to power is not listed (uncommon device) either do a internet search for the manufacturer or use a electronic clamp meter to measure the current while the appliance is switched on. Measure the current (Amps @ AC current). This can then be used to find the wattage value via this equation: watt = amp × volt. Voltage in South-Africa is AC 220V (50 hertz)

Example: A device that measures 2.2 amps at 220V = 484 watts.

Alternatively as a more advanced user you can measure your power draw directly on your Power Distribution Board. However this is dangerous to the uninformed and best suited to a qualified electrician (but will yield a very accurate result)

Once you have a sum of total power requirement for your home/business you have the information needed to make the decision on a backup power generator.

Fossil fuel power backup generators have been and probably will be for some time the most effective backup power sources in relation to cost and ease of use. Now that you have a size to go on the next step is to fit that to a machine.

The Best practice is the make sure your backup source is capable of providing 15 percent more power than your average use.

For example you have noted your household requires 4500 watts of power. This is 4.5 kW of power on average. The ideal power source must provide at least 5500 watts (5.5 Kw) of power.

The reason for overshooting is that certain appliances such as fridges require a higher amount of power when switched on for a few seconds. In other words when you switch everything back on your household will draw approximately 15 percent more power for a brief few seconds.

The generator is manufactured to handle a brief surge of power but only for a few seconds. Keep to the manufacturers specifications and you will never overload the generator.

Step 3

When you know how much power you require take a look at our range of generators

Once you know how much power or size you need head over to our power generator range page and make a selection. We have similar models in Diesel and Petrol. Either fuel does not make a difference in the working of the machine however for Silent type a diesel machine is more beneficial. Choose a machine that you can easily obtain fuel for based on your location.

Generator Prices and Specs Link: http://www.adendorff.co.za/Products/Generators

Thank You for Reading

120 thoughts on “How to choose the right size of generator

  1. Lance Heydenrych says:

    I am looking for a 1kw to 2 kw silent diesel generator to run our fridge and deep freeze for use in a power shedding application. We cook on gas.
    And where is the nearest Ardendorff Branch to Balfour or Heidelberg?

    • Francois Landsberg says:

      Hi, the nearest would be our Vereeniging Store. We stock a 2kw model and larger options too please visit our store locator link at the top to contact the store in Vereeniging.

        • Francois Landsberg says:

          We have stores all over the country use our store locator page at the top of our website or simply type in adendorff in google and it will show you the closest branch to where you are.

        • Francois Landsberg says:

          In most households a 7kw (8.5 kva). But these are backup machines and geysers hold their temp for over a day. There is no real good reason you should consider running the geyser too. If you using this for load shedding you only have power loss for 4 hours. So no need to get a larger generator than needed. Also not connecting the geyser will save money on fuel since the machine will not be 100% clocked out to max load.

          • Brad says:

            Hi Francois,

            Would you be able to run a fridge, tv and some small electrical likes laptops and wifi with maybe a couple lights off a 3.7 kva generator ?

          • Francois Landsberg says:

            Yes, that should be just fine, please switch on the fridge first and then the other appliances.

          • Henk says:

            Hi Francois, i do not understand the large power consumption you get for a freezer. My box freezer consumes 95w and my fridge /freezer a mere 260 watts.My tv about 100watts. So without geyser, a 3 kw generator for me is more than enough. Does most people have old appliances or why is their consumption huge?

          • Francois Landsberg says:

            True but that’s the running power. In order for the freezer to work, it must build up pressure so the motor spikes to about double for a few seconds so it’s like running double the amount of fridges for a few seconds.

    • Francois Landsberg says:

      Hi, there please visit our generator range. The link is below the infographic under generators. We have detailed info on each generator along with pricing.

    • R says:

      Hi LJ
      Any motor requires 5-6x it’s rated current to start. Your cooling unit would therefore require 25-30kW generator. Please also remember to derate at altitude by 1% per 100m.

      • Francois Landsberg says:

        Thank goodness we have some smarter people than us on here to answer these questions. I was a little unsure about starting current. Thank you R

      • D says:

        Hi LJ

        I am sure that you have resolved the issue with the your cooling unit. User R above is correct in what he is saying, however, this only applies to 220V machines at that rate. Three phase motors and units rarely have more than a 10% spike in amperage on start-up due to the windings being different. You will however experience an issue if the machine was only connected to one of the three phases, as opposed to being connected onto all three phases.

    • Francois Landsberg says:

      Just a quick estimate but a 5kw machine should do it. We are not familiar with the power draw on the compressor on the aircon though. I would recommend taking a look at the electrical panel on the radiator perhaps they have a wattage listed there?

  2. Kwena says:

    Please advise 2 fridges, lights for 4 bedrooms, alarm elec fence, cameras, garage door, gate motor stove, how many kwts Generator should I buy.

    • Estelle says:

      We bought a 6,5 genrrator from Adendorfs. It is struggling to give power for our house all appliances are off except TV and a few lights . The lights are flickering, the LED lights are going off completely and then back on again, repeatedly. What could the problem be?

  3. YUSUF says:

    Hi Francois

    I need a generator to power a few lights, a fridge and a freezer, TV & PC (alternativley). will the 2.8kva currently advertised for R3700 be sufficient?

    Kind regards

  4. Mike says:

    Francois,
    If I am looking to put in a silent generator for my entire house with automatic switch-over, and my house has a 63A breaker, would the house require approx. a 17KVA single phase generator ?
    Calc assumption 63A x 240V at 1.15 for start-up. I am assuming 63A because at that rating my board does not trip, having a 250L geyser. Went with the upper limit of 220-240V and added 15% for extra capacity on start-up load.
    Am I over-sizing or under-sizing?

    • Francois Landsberg says:

      Yes and no. For that size, we have only been able to source 380V machines since you can’t offer that kind of current on the circuitry of a 220V machine. 380V machines can be connected up to supply you but you will have to speak to a qualified electrician and have him take a look at your board. Take a look under our generators here and see our 20 kva machine with an ATS (autostart): https://www.adendorff.co.za/product/mac-afric-20-kva-16-kw-standby-silent-diesel-generator-ats-380v/

      remember on a 380V you need to use all phases equally so you can’t just hook it up with 1 220V output. Otherwise, the alternator is not balanced and you will gradually shake the machine apart.

        • Francois Landsberg says:

          Hard to say as every welder needs different current but I would not advise it. Welders need quite a lot of current and that machine only provides around 22A. At 100A an inverter will draw about 16-22A depending on how hot the welder is.

  5. Karin says:

    Please advise 2 fridges, 1 freezer, lights for 3 bedrooms, alarm, cameras, stove, electric kettle, cell phone chargers, how many kwts Generator should I buy. What hind of generator is best, petrol or diesel. And is is it more adviseable to buy an invertable generator?

    • Francois Landsberg says:

      Inverter machines are more silent and efficient but come at a much higher price. At this stage, we do not find them good value and for a home that size you will have to make a massive investment. For 2 fridges and the rest, a 7kw is recommended, you can make a 5kw work but might have to switch on the fridges 1 by 1 to prevent current spiking. Diesel vs petrol is more about preference but we have seen diesel is more efficient longterm and the engines can last longer over the years, however our petrol machines last a very long time too. Diesel open frame machines are also noisier though. Diesel machines are a better option if you live on a farm or outlying are and have better access to diesel (for example you have farm implements on site and use a tank)

  6. Katryn Snyman says:

    Kan jy vir my asb ‘n prys gee op 2.5kva kragopwekker en waar in Pretoria kan ek gaan kyk. Dankie Kan jy asb dit vir my email.

  7. Jenny Martens says:

    Hi

    What size petrol generator would I require to run 4 fridges, ignite a gas geyzer (I have converted over to gas), 3 T.V’s. WiFi, 2 computers, cellphone charging, inside lights for a medium house, 2 garage doors, electronic gates and maybe a microwave at times. I have gas cookers so dont need the stove.

    • Francois Landsberg says:

      A 7kw should be able to just about manage that, but a 10 kw would be recommended. This is just an estimate so we recommend to do an actual load test on your DB board to get the maximum current draw.

  8. Jonathan holl says:

    Good Day
    I am looking to run our office which is held by a 3 kva true on-line UPS.
    What size generator do i need to run this?

  9. Le Roux Jordaan says:

    Francois, n persoon het drie fase toevoer, voorsien drie fase na huis, kantore,werkswinkel en n kleiner huis. Net die boorgate is drie fase pompe wat se aanvraag oor die drie fases gebalanseer is. Wat is die persentasie verskil tussen fases indien een of twee fases se aanvraag meer is as die ander fase,bv, indien een fase 16 Ampere trek en die ander fase 10 Ampere ens. Enkelfase toerusting in die huis, kantoor en werkswinkel kan die fases se aanvraag laat verskil. Kan die generator bv. op een fase 16 Ampere hanteer, op n ander fase 10 Ampere en bv. op die ander fase 6 Ampere op een gegewe tydstip, of wat is die maksimum verskil in persentasie tussen die fases op een gegewe tyd? Ek hoop my vraag is duidelik.

    • Francois Landsberg says:

      Ja sien soos vorige vraag. Ons kennis is kerp op wat die masjien gee. Alhoewel hierdie is n gesprek wat jy met n kwalifiseerde elecktrisian moet he. Daar is manier om hom te balanseer en dit hang af hoe hy dit konekteer.

  10. Le Roux Jordaan says:

    Dag Francois, 12kw drie fase gen wat enkelfase toerusting in n huis, kantoor, werkswinkel en kleiner huis bedien. Wat is die persentasie verskil maksimum tussen fases wat gebruik kan word, m.a.w. indien een fase 16 Ampere trek, die ander fase 9 Ampere en die derde fase bv. 10 Ampere. Wat is die meeste wat die fases mag verskil in Ampere? Ek vertrou dat my vraag duidelik is.

    • Francois Landsberg says:

      Ek sal nie meer as 10% nie. Dit is moelik om dit op te stel sodat dit gebalanseer is. 15% op die meeste. Jammer vir laat reply ons comments hier was offline tot nou toe.

    • Francois Landsberg says:

      We generally don’t recommend using elements and recommend gas. However, the stove by itself will probably be too much just by itself. You will need at least 10kw for both on our estimates.

  11. Felix Maringe says:

    What size generator do I need for a three bed lighting, two lounges lighting, TV , two fridges, garage door, alarm. Gas stove???

  12. Marius says:

    Good day

    We have a 4 bedroom house (all rooms on LED lighting), 1 x 150L normal geyser and a 50L geyser, 1 fridge, 1 deep fridge (210L), 3 Tv’s, normal 4 plate stove. Wi-Fi and 3 x OVHD units what will be the ideal size Generator to buy?

  13. Albert Ruthenberg says:

    You mention in this article “In the article below there is a comprehensive list that shows the average power requirement of common household appliances.”
    Where do I find that article as see no link or similar.

  14. Craig Kisten says:

    Hi,

    What size generator i will need to run the following:
    QLED TV,
    DSTV DECORDER
    FIBRE ROUTER
    24000 BTU AIRCON
    FRIDGE/FREEZER COMBO
    GEYSER
    ALARM SYSTEM
    THREE ROOM LIGHTS

    • Francois Landsberg says:

      Hi, we aren’t sure exactly how much wattage the aircon would take you can measure it with a tester or find out from the manufacturer. The geyser should be between 2 – 3 kw so a 7kw 8.7 kva machine should be ablt to handle it. But it’s recommended getting an accurate measurement from an electrician. This should be fine for a 7 – 10 kw machine depending on if you are willing to witch the geyser of while you have load shedding. We recommend this.

  15. SATESH says:

    Kindly advise size generator I need to use to run 3 desktop computers, 2 laser jet printers. Modem. Switchboard with 2 extensions. 2 fluorescent lights and 25 down lighters

    • Francois Landsberg says:

      Hi, downlights are usually halogen and need some power. We can estimate a 7kw machine could be enough but you can only know this by having an electrician do a load test with all these appliances on. If lights are LED a 5kw might even be enough.

    • Francois Landsberg says:

      Yes due to high demand and load shedding the silents are all out. We get stock about evet 2 months depending on customs. We don’t have a date yet.

  16. M says:

    Hi Inam looking for 15kva for residential use with an automatic switch? If not 15kva then 12kva would it make a massive difference between the two?

    • Francois Landsberg says:

      Hello due to excessive costs to performance ratio the smallest machine we keep with an ATS is a 20kva Machine. Smaller machines are over expensive to the customer for the supply even when considering an ATS.

    • Francois Landsberg says:

      This depends on the type of hammer since more commercial units needs allot of amps. We would say at least 4kw but cant say without a proper load test of the hammer under stress.

  17. Steyn Marais says:

    Hi Francois
    I have bought a 8,75 KVA generator from Adendorff Cape Town today.
    Will this run an average home?
    I understand that it has limitations, but on average all the eletric equipment in a house are not used all at the same time.
    So, if I restrict, say, the swimming pool, will I be able to run 2 aircons of 12000BTU or 1 of 18000?
    My stove is on gas, as well as my geyser.
    From what I heard from all the “experts”, is that this will be sufficient to keep all my electric equipment on?
    If there is too litle supply, will the generator just cut out?
    Looking forward to hear from you.

    • Francois Landsberg says:

      Hi this should be enough but we are not 100% sure how much power an aircon needs there should be some kind of power info on the radiator unit to give you more info. Same goes for swimming pool since there are many sizes of motors depending on the size of the pool

  18. Nic says:

    Hi Francios,

    At my office I have 10 Desktop PC’s (3 with two 15″ monitors), 20 LED downlights, one small bar fridge/freezer and one printer. What would you suggest?

    • Francois Landsberg says:

      Depending on the size of the power supplies considering most are around 400w which needs about 4kw. Lights take very little so a 7kw should be enough. This is a little speculation we recommend doing some kind of load test.

    • Francois Landsberg says:

      All our machines except for the 950w model have AVR devices (auto voltage regulator) so they are safe for appliances. Inverters are safer but are more expensive for the size. We do not sell inverters.

  19. Megan says:

    hi
    Someone advised I need a 2.8 inverter to run my TV, WIFI and 1/2 lamps, for a running time of 2 hours. Is this the best thing? Is it about the size of a car battery?
    thanks

  20. Ntombi says:

    i have one fridge , 100L gyser 3 TVs, 3 explore decoders, lights for 10 rooms and one rooms with 8 down lights.
    what size of a silent generator do i need

    • Francois Landsberg says:

      Because of the geyser at least an 8kva. We do not have a silent machine in that size. we have a 6kvs diesel silent then we go to a 20kva machine. 20kva machine has an ATS as well.

    • Francois Landsberg says:

      Hi with stove 8kw (only 1 plate) & kettle. Without Stove & kettle, a 4kw would be enough. We recommend avoiding elements and maybe have a small gas bottle for instances where cooking is needed while load shedding is happening.

    • Francois Landsberg says:

      For now, we have no info. Our suppliers are dealing with some serious problems (you might have seen the news) so at this stage, we know shipments are delayed. But we do not have an estimate yet.

      • Cheryl Boudan says:

        Is the installation of a generator expensive for domestic use, run 2 tvs, wifi, laptop, fridge and stove, 3 lights, kettle, not too worried about geyser. Automatic switch.

        • Francois Landsberg says:

          Hi, it’s not usually although most people just run a cord to their devices since the generator is only needed from time to time. We do recommend connecting the machine to the switchboard and using a change over switch for safety reasons. You must contact an electrician for a quote on installations. We do supply generators, but we do not offer installation services at this stage.

          You can use a manual switch.

  21. Graham says:

    Maybe I’ve missed it, but nowhere does anyone mention the acceptable noise level for residential areas. In our area (Fourways) it’s 55db maximum. None of the cheaper made in China generators come close to meeting the specification. They are 90db +. Most good quality inverter generators (like the Honda EU6500) do meet the specification and they also use a lot less fuel which also means less emissions.
    The other thing that people are not well informed about is that they can have their db board reconfigured to run all non-heating appliances off the generator using a change -over switch. You don’t need to run your pool pumps, stove and oven when there is load shedding. Everything else – including household aircons, TV, lights, fans, garage doors and even a kettle or toaster, will run just fine off a 6500W inverter generator. You can also run your washing machine and dishwasher during the day if you don’t run them at the same time. I know this very well from my own experience with my Honda EU6500. BTW. It will also gently cut out automatically if it’s overloaded although I have never had that happen. I bought one of my inverter generators from Adendorf about 10 years ago. Its definitely worth the extra cost.

    • Francois Landsberg says:

      I think considering the national crisis and businesses losing money due to load-shedding most people will be tolerant of the noise. Any petrol engine will be considered loud but at this stage, most people don’t really have a better alternative. Solar panels & batteries are one but the costs can far exceed fossil fuel options for a similar output. It’s true what you say about the appliances most people should only run the needed things example TVs, lights, internet and security. Power is offline for 4 hours so fridges and geysers are not needed. And we always recommend our customers to consider gas for cooking.

    • Francois Landsberg says:

      Meeste haardroërs trek so 2000W, daarom sal jy ‘n groot masjien benodig. Tenminste 10kVA, omrede jou Ampere meer as 28A gaan wees.

    • Francois Landsberg says:

      Sorry, but we are out of stock on every single smaller machine right now. Loadshedding in combination with serious issues overseas have hit our supply hard. We are doing all we can to get more.

    • Francois Landsberg says:

      Because of the fridge, we would recommend a 4kw. You can use a 2kw, but then you must only switch on the fridge 1st and then the other appliances. Fridges need more power to operate than most of the other appliances.

    • Francois Landsberg says:

      We do not recommend this. We sell generator welding machines since their electrical components are designed for a high input current, which is needed by the welding machine. Our generators are manufactured to be a reliable backup power solution (used when needed), not for supplying as a mains power source.

  22. Clemence Smith says:

    Hi,

    I have my name on the waiting list at your Bloemfontein branch for a MAC-AFRIC 8.75 kVA (7 KW) Standby Petrol Generator. It is out of stock for a while now. Any idea on when you will have stock again. The local sales personal do not really have insight in national procurement strategies.

    Thank you.

    • Francois Landsberg says:

      Hi, its because none of us do. If it’s here it’s here. Due to customs and the panic over in the east, we actually have no due dates until they land.

    • Francois Landsberg says:

      A 2kw (2.5 kVa) will be more than enough. A smaller 1 kw (1.2kVA) will also work with a shorter running cycle (4 – 6 hours)

  23. melanie says:

    Good Day
    My name is Melanie i live in an area called Ennerdale JHB we have been advised by city power due to the informal settlements around us tapping into our power our sub station is at risk of overloading and to avoid total shutdown of this power station they are now looking at implementing like a kind of load shedding meaning anytime on a daily basis between 16:00 and 23:00 hours we will be switched off i am looking for advise on which options there is available for me to have my essential items in working condition during this time the items i would like to still run when we have these outages is my fridge its a fridge to and freezer bottom i have a big microwave does size make a difference or should i purchase a small one i can use for outages? below is a list of the items i would like to have running
    Fridge
    Microwave
    Kettle
    My telkom wifi i have a plug in unit
    One TV
    A few lights does type of globes make a difference like the bulbs and which is recommended for running a generator?
    A few plugs where we can charge our phones and operate our laptops
    I aslo want to ask when it comes to running a stove i have a cable 4 plate stove with oven would i then maybe have to buy a 2 plate spiral stove? I am looking for options that would not put strain on the generator
    I have aircons in 3 bedrooms but am not sure if that will use more power from the generator, if not can you answer if i have them connected and also if i dont.
    I am also looking for a unit that i do not have to go out and switch on when the outage occurs is there something that automatically kicks in when power goes off and also when it goes on again it must go off
    How does one maintain a generator like i know for my aircons i do a service once a year so for a generator how does this work and where does it go to?
    And this generator will be outside cause i know they make a noise is there maybe a low noise or no noise options and prices.
    Someone said petrol is better is that so?
    Can i build a i am going to call it a kenner type of thing to protect my generator from thieves with burglar bars or something around and install a beam so that when someone is there an alert in the house alarm me.
    During lockdown level 4 are we allowed to purchase this generator.
    Warranty on it will be?
    My email address is Melanie.Block@standardbank.co.za
    Thanks
    Melanie

    • Francois Landsberg says:

      For lights use power-saving ones or even better LED. The stove, fridge, and geysers are the only things you need to worry about. The stove should be avoided and consider getting a gas plate for situations where needed, the Same thing for kettle use gas energy, and even consider switching your electrical stove for a gas one. The machine can be used outside if under covers and kept dry (out of sunlight). We allow sales of our products at level 4. We do not do security like this, but many security service people can maybe build an enclosure. Because of the range of things you asked for its impossible for me to accurately suggest a model. You need to have a load test done with your appliances on and decide which ones you need the most, and test with them switched on. But if you exclude the heat elements a 5.5 kW or 7kw can work. Petrol machines are cheaper but make more noise. Diesel closed types are more silent but they are only 5.5kw and then go to 10 kW in size. To service, the machine return it to any store. And we provide the needed parts, for general parts you can get engine oil and spark plugs at any car spares store. Service is when the oil becomes too thick, it’s hard to say how frequently as it depends on how much power is used when the machine is running. But the first service is around 50 hours. All our machines are under a 1-year warranty. As for the auto start, the smallest auto-start machine we have is a larger 20kw silent diesel since the pricing for the size on smaller auto-start units is not economical. The other machines we sell are all key start and cannot be used with an Auto Start.

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