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Power Consumption of Cooking Appliances - Summary – Rainbow Power Company

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Cooking appliances on an Inverter Cooking our food uses a lot of power. You could try solar cookers or ovens which work directly off the sun. These are a slow type of cooker, that retain high levels of food nutrients and work well. However, apart from sunlight you also need patience. In general, we suggest that if you are on a solar, or other Renewable Energy system, you would do all of your cooking on gas or on a wood stove. However, in good weather, you may often have a surplus of power and some forms of electric cooking are surprisingly efficient. I recently upgraded my solar system under the AGO rebate program. The system (24V) is made up of eight 80W PhotoWatt and four 55W Arco solar modules together with a Selectronic SE12 inverter. On 24V this inverter is rated at 700W continuous and 900W for half an hour. Using Rainbow Power Company's software I chose to design the system to meet all my loads, even in the 'worst' month. This means that my regulator will be reducing my available solar charge current during the remaining eleven months (based on average weather conditions affecting actual daily solar insolation). My Plasmatronics PL40 regulator has the ability to divert the charge current or turn on other loads when the battery is fully charged. Water pumping is sometimes a good choice, however I have an abundant supply of gravity feed water. The design software suggest that most months I'd have the power from 1 to 2 of my 80W solar modules to spare. When the price of LP gas went up recently, I decided to look into electric cooking appliances. A summary of the smallest (lowest wattage) appliances is listed below. I found K-Mart to be the best place to find small, low wattage gadgets. ApplianceCost (AUD$)Watts(on label)Watts(DC)*Slow cooker / crock$100285----Bread oven$279470480Snack oven$53650660Coffee maker (5 cup)$38685704Frypan (230mm)$74700752Sandwich maker$40750803Toaster$19900982Hot plate$3511001099Microwave oven----1200----Electric jug----1400---- *All measured wattages were taken on the DC input side of the inverter and measured by the Plasmatronics regulator. The actual battery voltage was used to calculate the figure. This was usually about 25V. Slow Cooker: I haven't bought this appliance but I hear that they are great for cooking some foods. Bread Oven: See 'Bread-makers' tab. They use between 250 and 650 Wh to make a loaf of bread. The average was 330Wh. A great way to use your excess solar power! Snack Oven: The Ronson snack oven is designed to heat pre cooked food like grilled cheese sandwiches. The top griller used 365W, the bottom one used less at 285W and together they used 660W on my inverter. It takes about 8 minutes for a sandwich (88Wh). Larger oven grillers are available to cook meat etc however they are rated at 1500W. Coffee Maker: My Mistral coffee maker is perhaps the best bargain! It is described as a '5 cup' unit - three 500ml mugs by my reckoning! It makes a mug full of great coffee in about 3 minutes using a miserly 59Wh of power. A bargain buy at $38! Frypan: This Black & Decker 230mm skillet is a bit small for anything larger than 2 medium sized chops or 3 - 4 eggs. However, it worked well. It takes about 12 minutes or 150 Wh to cook two thick steaks or fish cutlets. Because the element is bonded to the base of an electric frypan, I think they are more efficient than using an ordinary one on a hot plate. The frypan was not supplied with a cover though later I saw a similar sized Sunbeam one with a tin lid. Haven't been able to find a glass lid to fit it as yet. Larger 'family sized' frypans were rated at between 1200 - 1600W. It cycles on and off every few minutes when set to the lower temperature settings. Sandwich Maker: These are similar to waffle makers and you can prepare fruit or savoury hot sealed sandwiches in it. Takes 5 minutes or 67Wh to prepare two pieces. Toaster: Doesn't need much description - it takes 2 to 3 minutes or 41Wh for 2 pieces of toast using a 2 slice model, a 4 slice model used about 16wh per slice, plus 59Wh for the mug of coffee! Our technician Ray later found a 700W model and tried it out - it drew 31.5 amps on the DC side of his inverter and took 2.2 minutes on setting 4 to make his wholemeal toast. That is about 30Wh per toasting. Hot Plate: I initially chose not to purchase this appliance because its 1100W rating was in excess of the 900W thirty minute rating of my inverter. Interestingly, Selectronic give a second 45A thirty minute rating on this inverter which is actually 1100W (on the DC side) if one's battery voltage is 25V. My other cooking appliances were still not using my surplus power which infuriated me each evening when I turned on my LP gas! I took a punt and purchased a Tiffany brand model. I was pleasantly surprised when it only drew 46A @ 25V and my inverter could cook the evening meal. On the lower heat settings it cycles on and off for about a minute at a time. It takes about 7 minutes to bring 750ml of water with broccoli, Brussels sprouts and corn on the cob to boil and about 3 minutes of simmering thereafter (about 156Wh). Fish and meat takes 6 - 12 minutes to fry depending on how thick it is. In all, a meal for two consisting of boiled veggies and fried meat/fish used an average of about 325Wh. However, meals with foods like rice, dried beans etc would take a lot longer to cook and use up more power. Cooking times are also affected by variables such as ambient temperature, type of pot etc. Microwave Ovens: See 'Microwave Ovens' tab. Boiling Water An electric jug or kettle is not usually recommended on a solar system, as they require quite a lot of power. Most electric jugs are 1.5 to 2 litres in size and are rated between 1600 and 2200 Watts. I managed to locate a small electric kettle at Kmart, which was rated at 1250 Watts. It holds one litre (4 coffee cups). The model was a Kambrook KE9. Using my 1600 Watt Selectronic SA22 inverter it used 1355 Watts (54 Amps @ 25 Volts). With my water at 17C it took three minutes to boil 500ml or 5.5 minutes for one litre. Total power used to boil one litre was 5 Ah @ 25Volts. Bread-makers HOW I BAKED MY FIRST LOAF OF BREAD I recently upgraded my own solar system, thanks in large part to the new Australian Greenhouse Office 75% rebate, so I decided to purchase a bread maker. For those of you not familiar with this product, I'll briefly describe what it does. In simplistic terms, it bakes your bread with about 30 seconds of work - just measure your flour, water, yeast, salt and any other goodies you want to put in your bread. Select the loaf size, crust colour, flour type and the time you want your loaf to be baked by and the machine does the rest! Over the next 2 - 3 hours, the unit goes through several cycles: two types of kneading, a rise, first punch down, second rise, shape, third rise, bake and an optional keep warm cycle. I did some research first. I had a look at a Choice magazine article (published by the Australian Consumers Association). They tested 11 models and reported that all but one baked an excellent loaf of bread. They calculated the cost (with grid electricity) at less than half that for a store purchased loaf. The article suggested that one look for the following features: adjustable loaf size, removable pan and lid for easy cleaning, timer, keep warm function, crust colour selection, capability to make jam, pasta and pizza dough, fruit/herb dispenser. We asked the author how much power they used and she reported that they used between 250Whrs and 650Whrs with an average of 330Whrs per kilo loaf. However, the Choice article didn't tell me how they'd run on my SE12 Selectronic Sine Wave inverter (700W continuous rating). I remembered some of our customers had given us some good feedback in this regard so I consulted the archived editions of the Rainbow Power Company's free email newsletter. Someone had earlier warned us that the Panasonic SD250 had problems even on a sine wave inverter. In the December 99 newsletter, Stephen

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