The Shed - - Generators - By Mark Beck­ett Pho­to­graphs: Mark Beck­ett

As win­ter ap­proaches and power out­ages be­come more likely, we thought it might be use­ful to iden­tify what you need to know about gen­er­a­tors, safety, their uses, and how to con­nect them to your home.

A ‘gen­er­a­tor’ is a mo­tor driv­ing an al­ter­na­tor to pro­duce power, and with the ad­vent of in­verter gen­er­a­tors (see my re­view of Honda in­verter gen­er­a­tors on pages 82 and 83) the ba­sics haven’t changed, but how they op­er­ate has.


Like all mo­tors burn­ing fuel, gen­er­a­tors give off car­bon monox­ide. This is a colour­less, odour­less killer that makes you fall asleep and doesn’t trig­ger any safety re­flexes in the brain, so it will kill you. While the fumes are deadly, the heat from the ex­haust out­let can also burn any­thing com­bustible if it’s too close.

In ad­di­tion, un­less you bolt it down, your gen­er­a­tor can and will move around, so you need to be ex­tra care­ful and check it reg­u­larly. Re­fu­elling is the same with any hot mo­tor, but if you’re strug­gling to pour fuel into a mov­ing, vi­brat­ing hole, then think again and switch it off.

The stan­dard mains sup­ply ties the neu­tral to earth, so the volt­age be­tween phase and neu­tral/earth is 230V. A gen­er­a­tor is float­ing, so the phase and neu­tral volt­age wrt earth can rise (just as if you are us­ing an old-fash­ioned iso­la­tion trans­former). Al­ways en­sure that you con­nect the gen­er­a­tor earth to the build­ing earth if you’re pow­er­ing part of the house.

As with any ro­tat­ing ma­chin­ery, keep­ing fin­gers out of harm is per­formed with safety cov­ers or de­sign. En­sure that cov­ers are left in place and re­place them if dam­aged.

For ex­tended power out­ages you can run parts of your house — I em­pha­size ‘parts’

Power ba­sics

Mains power in New Zealand is ap­prox­i­mately 230V AC and the fre­quency is 50Hz. The reg­u­la­tion spec­i­fies that the volt­age should be be­tween 200 and 250V, but it should re­main within six per cent of what you and your power com­pany de­cide. That’s not help­ful, as I can’t re­call hav­ing any dis­cus­sion with my en­ergy re­tailer, and mine mea­sures 240V. Mod­ern elec­tron­ics use switch mode sup­plies, so they tend to han­dle volt­age ranges from 100 to 250V with­out any ef­fort, but many other ap­pli­ances and es­pe­cially light bulbs are less happy with high (or low) volt­age.

As men­tioned, the AC fre­quency is 50Hz and the reg­u­la­tion spec­i­fies it shall be within 1.5 per cent. While it doesn’t worry most elec­tron­ics mo­tors di­rectly con­nected to the mains fol­low the fre­quency, so the speed will change. Thank­fully the power com­pa­nies do con­trol fre­quency very tightly.

New Zealand houses tend to have 63A (or 40A per phase in mul­ti­phase in­stal­la­tions). This equates to 15.12kW (or 9.6kW per phase), which is sig­nif­i­cantly more than the three gen­er­a­tors in the re­view I un­der­took for this ar­ti­cle.

There are per­ma­nently mounted gen­er­a­tors that pro­vide power dur­ing a mains out­age. Air­ports have them for light­ing, hos­pi­tals for keep­ing ser­vices run­ning, and some large of­fice build­ings to al­low the lifts to go to the ground floor and dis­charge pas­sen­gers.

Most of these are large diesel units fitted in the base­ment, but I’ve also seen a num­ber of smaller-sized units fitted out­side in a self-con­tained cab­i­net.


For this ar­ti­cle we chose three of Honda’s ‘por­ta­ble’ in­verter gen­er­a­tors: EU22i, EU30i, and EU70i. These are all petrol pow­ered, with the EU30i and EU70i also hav­ing an elec­tric start.

The rat­ing is cov­ered in the re­view, but ba­si­cally the num­ber re­lates to the max­i­mum kilo­watts (or kilo­volt am­peres [KVA]), that is, EU22i is 2.2kW max. To check which size you need, you sim­ply add up all the loads you wish to run at once.

All por­ta­ble ap­pli­ances have a plate show­ing the volt­age and ei­ther power (W) or cur­rent (A) that the ap­pli­ance con­sumes when run­ning. You mul­ti­ply volts by am­peres to get the power in watts. For ex­am­ple: 230V x 1.5A = 345W (with 1000W equalling 1kW). Mo­tors usu­ally re­quire two or three times their run­ning cur­rent dur­ing start­ing, so un­less it has some form of speed con­troller, in­clude this in your siz­ing equa­tion.


Many mar­ket stalls use a small ‘silent’ gen­er­a­tor to pro­vide power while they run. You usu­ally find these hid­den out the back and un­less you no­tice the power cord, some­times you don’t even re­al­ize they are there.

Un­til the ad­vent of higher pow­ered bat­tery tools, if you wanted to do some­thing where there wasn’t power, you’d need a gen­er­a­tor. Builders and other trades of­ten use them when the site has no power or the ren­o­va­tions make it safer to have the power dis­con­nected.

Camp­ing (or glamp­ing) at non­pow­ered sites is an­other pop­u­lar use, but un­less you’re on your own, it’s best to use a quiet model like the Honda EU22i.

There are baches and other off-grid lo­ca­tions that have so­lar (or wind) to charge bat­ter­ies that con­nect to an in­verter for light mains loads. They of­ten have a gen­er­a­tor to run larger do­mes­tic ap­pli­ances and as backup to top up the bat­ter­ies.

Run the house

For ex­tended power out­ages you can run parts of your house. I em­pha­size ‘parts’ be­cause even the EU70i can only pro­vide 5.5kW, which could power a mod­ern oven, a quick-boil jug, maybe the TV, and a few nor­mal lights at the same time.

Dur­ing a power out­age you need lights for cook­ing, the toi­let, and a cen­tral space. The TV might seem a lux­ury but it will up­date you on the weather and pro­vides a wel­come distractio­n. If you have gas hot wa­ter, the unit will re­quire power and this as­sumes you still have run­ning wa­ter.

Heat­ing can be an is­sue, but ex­tra lay­ers, blan­kets, hot-wa­ter bot­tles, and ther­mals should pro­vide some com­fort.

If you live in the coun­try, the sep­tic tank will be fine for a week, and the chest freezer should stay cold for sev­eral days. The wa­ter pump may need to be con­nected to top up the header tank or pro­vide wa­ter, but we’ve found that the bath pro­vides 50–100 litres so fill­ing the bath pro­vides wa­ter to top up the toi­let cis­tern after flush­ing.


It’s likely that the broad­band con­nec­tion will still pro­vide sig­nal, but the mo­dem will need power. If your phone is still the old cop­per-pair, the cord­less phone won’t work, so al­ways keep a corded phone avail­able (as the peo­ple of Christchur­ch dis­cov­ered eight years ago). For us the phone line kept work­ing but the lo­cal mo­bile-phone site stopped once the bat­ter­ies went flat.

You’ll need to en­gage an elec­tri­cian to pro­vide a switch on or near the switch­board, and maybe swap a few cir­cuits around inside the switch­board. He’ll also need to fit a socket some­where to ac­cept the power from the gen­er­a­tor. This needs to be a suit­able size to en­sure that the pro­tec­tion cir­cuits will trip if there is a fault.

Ob­vi­ously this is eas­ier when the house is be­ing built, but it’s still pos­si­ble later, and hav­ing lived in the house you will prob­a­bly have a bet­ter idea of your needs.

Many … ap­pli­ances and es­pe­cially light bulbs are less happy with high (or low) volt­age

The big­gest ad­van­tage of the Honda in­verter range is the abil­ity to con­nect two or three units to­gether to dou­ble or triple the power out­put. This means that you can carry two EU22is to your site to pro­vide power, as op­posed to a he­li­copter trip with a larger unit.

The EU22i and EU30i also fea­ture a sep­a­rate 12V DC out­let. These pro­vide 8.3A (99.6W) and 12A (144W), re­spec­tively, to boost charge your so­lar or au­to­mo­tive bat­tery.

The EU22i pro­vides 1800W (2.2kW max.). This is the small­est, qui­etest, and light­est unit at 21kg, and while it won’t run your quick-boil jug (2.4kW) it will run a num­ber of smaller ap­pli­ances and power tools.

The EU30is pro­vides 2.8kW (3kW max.). Weigh­ing 59kg, it is heav­ier than the EU30i but has a larger fuel tank and slightly higher power out­put than its wheeled brother. The EU70i pro­vides 5.5kW (7kW max.) and at 118kg is not ex­actly por­ta­ble. It does have han­dles and wheels so you can move it around when you want to run it.

‘Eco Throt­tle’ is the name that Honda has given to the sys­tem that ad­justs the en­gine speed to suit the load. With the in­verter tech­nol­ogy the out­put volt­age and fre­quency re­main con­stant, re­gard­less of the en­gine speed. This means that the mo­tor runs more qui­etly and uses less fuel

To check which size you need, you sim­ply add up all the loads you wish to run at once

when the load is light. If you try this with any older cheap gen­er­a­tor, you’ll find the out­put volt­age goes out­side the range and can cause dam­age to elec­tron­ics if it goes too high.

I have an older 2.2kW gen­er­a­tor and there is no com­par­i­son with the EU22i. This is quiet, light, doesn’t walk ev­ery­where, and is eco­nom­i­cal. I dread us­ing mine as the volt­age is never con­stant, so I’m try­ing to work out how to make this new one ‘dis­ap­pear’, rather than giv­ing it back.

Which model you need de­pends on what you’re try­ing to do, and it pays to speak to your lo­cal dealer to find the model to suit your needs. They can also sup­ply ex­tra at­tach­ments to suit most needs.

Part of my test was to check the out­put volt­age and fre­quency, and these were sur­pris­ingly sta­ble. The volt­age will dip a lit­tle when you sud­denly load them run­ning in Eco Throt­tle. This is to be ex­pected, as the gen­er­a­tor has to de­tect the drop, open the throt­tle, and sta­bi­lize. If you have volt­age-sen­si­tive equip­ment, turn off Eco Throt­tle, plug in the load, then switch it back on. The fre­quency re­mained rock steady re­gard­less of speed or load, which is cer­tainly bet­ter than the old-style gen­er­a­tors that I’ve grown up with.

Un­less you bolt it down, your gen­er­a­tor can and will move around, so you need to be ex­tra care­ful and check it reg­u­larly

When we moved out into the coun­try we were warned that the power some­times fails, and with few cus­tomers on the road, there could be de­lays in restora­tion. I had planned to wire the switch­board for a gen­er­a­tor con­nec­tion that would also power the wa­ter pump (120m away), but some­how the ca­ble from the switch­board to out­side got over­looked, and hence it never got com­pleted. As such, dur­ing the last ex­tended power out­age, the camp­ing gear got dragged out for lights, and the gas cooker worked just fine for cook­ing and hot wa­ter, and we used the gen­er­a­tor to watch TV via an ex­ten­sion cord out the win­dow.

Place­ment is im­por­tant

Most por­ta­ble gen­er­a­tor electrics are not IP rated, so you will need to con­sider the place­ment to avoid them get­ting wet, re­mem­ber­ing the ex­haust fumes and heat, and the abil­ity to top it up with fuel. Camp­bell at OMC Power Equip­ment showed me the ex­haust de­flec­tor and ex­tended fuel tank the com­pany can sup­ply. This helps with some of the prepa­ra­tions, but you need to en­sure that you have spare fuel on hand and cy­cle it to make sure it doesn’t go stale.


Hav­ing ev­ery­thing pre­pared and ready to go is great, but when it’s cold, dark, and wet (or snow­ing) can you man­age to get it work­ing? Can your part­ner or chil­dren man­age? Are the in­struc­tions clear enough?

There is noth­ing like hav­ing a test to prove it works, but see if you can make it close to re­al­ity. I’d also sug­gest run­ning it for three or four hours, as you won’t wear it out: while do­ing this ar­ti­cle I was shown a pic­ture of the hour me­ter from a Honda EU20 that had run 6100 hours and was still work­ing per­fectly.

The au­thor would like to thank Leon from Honda Power Equip­ment, Tim from To­tal Power Hire, and Camp­bell from OMC Power Equip­ment for their help and ad­vice in writ­ing this ar­ti­cle.

Above: A gen­er­a­tor res­cued from the base­ment of a build­ing be­ing de­mol­ished after the Christchur­ch earth­quakes

Right and be­low: Large gen­er­a­tors to pro­vide backup power

Honda EU30is and EU22i com­pared with a 20-litre fuel con­tainer

Ex­haust out­lets

Above left: EU70is with 32A plug fitted to al­low full power on a single ca­ble Left: EU30is front panel

Above: Volt­age (left) and fre­quency (right) of the EU22i

Be­low: Volt­age (left and right) and fre­quency (mid­dle) for the EU30is show­ing difference be­tween loaded and un­loaded volt­age read­ings

EU70is show­ing han­dles and wheels for mo­bil­ity

Re­dun­dant backup gen­er­a­tors for es­sen­tial ser­vices

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