Appliance Selection for Your Off-Grid Home
Appliance Selection for Your Off-Grid Home
Here are important points about selection of appliances and some wiring tips for solar electric homes. This is a little different than you might expect for utility connected homes, and the difference is essential. Be sure you understand these pages before shopping for appliances. Your electrician should understand these points when planning the wiring. Call Backwoods Solar if you have questions.
Lighting uses less power, if you have lots of local area “task” lights rather than a big central light. Use 15 - 20 watt fluorescent lights under cabinets close to the kitchen counter. Use a separate wall switch for each wall/ceiling light so you can turn on lighting precisely where needed. Several small lights save energy by giving more flexibility than one large central light.
Screw in light bulbs should be mostly compact fluorescent lights using about one quarter the power of regular bulbs while giving the same brightness and color. Get only electronic ballast models; they do NOT flicker. Light dimmers should not be used unless you have a sine wave inverter and the bulb specifically states dimming is OK.
Timer light switches are great for lights turned on and often forgotten, as in children’s rooms, closets, stairwells, and particularly basement and outdoor lights. Timers keep the peace when lights are frequently forgotten. The tap of a electronic timer button or a wind up light switch timer starts the light and sets the run time you choose from a few seconds to an hour, after which the light goes out. Windup light switch timers are in the lighting section of the website.
Motion sensing lights outdoors are great for arrival and departure. An AC motion detector will not turn lights on when needed unless you force your inverter to run full time. If the inverter is at idle (search) mode, the sensor will not work. A 12 volt DC powered motion sensor in this website is the answer. It's on duty all night with almost no power use.
Wall Clocks & Timers
Clocks should be quartz type, battery powered, not plug-in AC powered. Timers for automation or wake-up radio should be DC powered, not AC. Several timers are available in this website.
Windows based PC computers run on any inverter at this time, and we believe that Apple/Macintosh computers do not require a "true sine wave" inverter.
Laptop/notebook computers use internal batteries, and recharge from any small inverter using just 20 to 50 watts AC power. Most manufacturers offer an optional car cord to operate directly from a 12 volt battery at very low power.
Laser printers (and most photocopy machines) can be damaged by modified wave (not true sine wave) inverters. Inkjet and dot matrix printers are no problem, and use very little power. HP Laserjet printers automatically idle to just a few watts between printing, or a switch can be used to shut your printer off. An outlet strip should be used to switch off all computer equipment after shut-down to prevent phantom load leakage.
For best results, we recommend that the whole home/office be powered by a large true sine wave inverter. Alternatively, one of the smaller true sine wave inverters may be added for your sensitive electronics, and a separate circuit run from it in the battery room to an outlet by those devices.
Refrigerator / Freezer
Many standard refrigerators and freezers use so much power that battery charge is depleted very quickly. It is not practical to use most standard electric refrigerators or freezers with independent power unless you have a powerful water turbine generator. Super efficient refrigerators designed and tested for solar power, listed in this website, operate on less than half the usual power. Some carefully selected Energy Star rated conventional refrigerators using under 400 - 450 kilowatt hours a year may be acceptable if your system is sized to handle it and is what everyone at Backwoods except Shawn currently does!
Most clothes washers work fine with a minimum 1500 watt inverter. They consume 800 watts while running. A starting surge of about 3000 watts is required. New horizontal axis, Energy Star rated washers by Kenmore, LG, Whirlpool, Frigidaire, Maytag etc. use much less power, less water, and less soap than verticle axis machines. Most of them require a sine wave inverter and void their warranty when used with generator or inverter power but usually work fine.
Propane heated clothes dryers can be used; 240v AC electric heated dryers cannot be used.
Electric stoves are out. Propane or natural gas stoves with gas pilot light need no power at all. Optional spark ignition burners use very little power and work fine with inverters. DO NOT BUY a gas range with a glow-bar in the oven. It is an electric red-hot pilot bar that consumes 400 watts while the oven is used! Instead, look for one of two types of pilot light oven. An oven with regular gas flame pilot light is simplest. Or an oven that lights a burner by electric spark only when the oven is started, and then the burner goes off when the oven is finished heating. Both types are available on the Peerless Premier propane ranges sold in this website. Also the AC clocks in some ranges are phantom loads, keeping the inverter running full time. If so, disconnect wires to the clock so you can plug in the stove to use the oven light and spark igniters. Range hoods with light and vent fan work fine with inverters. Be sure to put a compact fluorescent bulb in it.
Dishwashers work fine with a true sine inverter, with one caution. There might be two high power heaters, one to dry the dishes and sometimes one to superheat incoming water. You should be able to disconnect or switch off these heaters to save a lot of power.
DC pumps use very little power and can pump to well depths of 200 to 800+ feet. Our 1/2 hp 120 volt AC pump can operate from inverter power and lift water 300 feet. And we even have a pump, the Grundfos SQ Flex, which accepts either AC or DC input and can lift water up to 820’. Avoid 220 volt models or higher horsepower than you actually need. The water pump section in this website has more information.
Stereo, TV, VCR, Satellite TV
A 20" tube style TV uses about 85 watts and usually works with any inverter. A 32" LCD uses about 125 watts and requires a true sine inverter. VCR and some satellite units use only 20 watts. SATELLITE TV works great on inverter power. A Direct Satellite System (DSS) uses about 15 watts. STEREO of good quality usually works with any inverter. TVs, VCRs and stereos with remote control are phantom loads, and still consume power when switched off. It is important to use a wall switch, or a switched outlet strip to cut all power from this equipment when not in use. A few large screen TVs and sensitive audio gear require true sine wave power.
Cordless Phone, Message Machine and Fax
Cordless phones typically work on direct 12 volt DC, very low power, to avoid keeping the inverter on 24 hours for so small a load. The DC-Isolator in the 12v Appliance section should remove line static associated with conflicting grounds. To determine if the cordless phone or answering machine of your choice is compatible with DC power, you need to look at the machine's wall cube that plugs into a 120v AC outlet. This cube will describe in writing the power needs of the phone or answering machine. It should state 120v AC input and then the output that gets delivered to the machine. The output you want is 9-15 volts DC.
Phone message machines use small amounts of AC 24 hours a day which adds up to a large load. As just described, a few message machines can be converted to operate direct from 12 volts for very low power use. Again you will need the DC-Isolator to avoid static. A cell phone functions as an answering machine and requires minimal amounts of power so is a great solution for a phone/answering machine IF you have cell coverage.
Telephone Beyond the Lines
If phone lines cannot reach your site, a radio relay phone link up to 15 miles line-of-sight can connect you to the nearest phone line. The radio link brings in phone, modem, answer machine or fax. Or a cell phone with a boosting antenna or amplifier may be the answer. Backwoods Solar does not sell this equipment. One source is KootenaiRadio@netw.com.
Direcway and Starband offer high speed satellite internet services, no phone line required. An excellent choice in most remote areas for off-grid homes.
So much power is consumed with so many running hours that air conditioning is usually considered impractical on solar power. The smallest window unit is possible with large power systems, but can add $5000 to power system cost. Evaporative cooling works, except where very humid. Low energy 12 and 24 volt DC coolers are listed in our DC appliance section.
Electric water heaters are out. Use a natural gas or propane heater from plumbing and hardware stores. Get one with a pilot light, not glow-bar ignition. Vent all gas appliances straight out through the roof. Avoid power wall vents that seem easy to install but use substantial power ever after. Or use a Bosch instant tankless water heater shown in the non-electric appliance section of this website. The tankless instant water heater saves gas. A wood fired hot tub heater is also in the non-electric appliance section.
Heater - Furnace - Hot Water Floor Heat
Use propane, natural gas, oil, or wood heaters and furnaces, never electric heat. Electric heat pumps also use substantial amounts of energy, less than resistance heat, but way too much for independent power. They are reversible air conditioners. Also beware of ducted forced air and blowers. Common in manufactured homes, the blower takes much more power than can be justified.
Cozy brand propane direct-vent (through the wall) heaters in the non-electric appliance section of this website save fuel because each room can have its own heater and wall thermostat. No circulation blowers are needed so they work with no electric power. This is the easiest and lowest cost heating installation.
Wood or gas furnaces located on bottom floor or basement in a multistory home allow heated air to rise by convection from lower to higher floors without powered fans or ducted blowers. Larger ducts for natural convection circulation can work with no power blower needed, or a very low power quiet DC fan from our DC appliance section to boost output. Our no power Caframo Ecofan or low power fans can also increase efficiency of gas heaters or wood stoves by moving air over the surface. Some home designs add a space along side a masonry chimney as a hot air duct to the upper floors, and perhaps also run water pipes through it. Each stairway should have a door to control rise of heated air.
Floor heating by hot water circulation requires power to circulate water. Use of 1/2 inch or larger floor pipes allows a lower power pump. Use separate DC circulating pumps found in the Pump section of the website and control each by a thermostat for its zone, rather than zone valves. We have seen problems using special boiler systems & zone valves. We have seen success using tank gas hot water heaters or the wood fired boilers that heat water directly in the storage tank. You can also warm water beds and compost toilets by circulating hot water from the tank through coiled pipes under them and back again. Remember floor circulation heating puts added demands on your power supply at the season when you have the least power. See Home Power Magazine issue 79 page 36 for more details.
Shop & Power Tools
Most hand-held power tools operate on 800 to 1500 watt inverters. Larger power equipment like table and radial saws usually work with 2500 watt inverters, though sometimes the motor belt needs to be slipped for easier starting on the largest equipment. Sinewave inverters like Outback VFX, Magnum MS or PAE or Schnieder XW work best for really large equipment. Wire feed welders and air compressors usually require 3500 watt or larger 4000 watt inverter. Select small wattage tool motors or use a generator to power larger ones. Cordless tool rechargers without a wall cube transformer plug must have true sine wave inverter power, and may be ruined on modified waveform inverters.
Phantom Loads - Appliances That Steal Your Power Even When They Are Turned Off
Some appliances need to be disconnected from power as completely as pulling the plug, when not in use. Remote control TV, VCR, DVD, stereo, microwave oven and office equipment (computers, fax, etc.) may use a little power 24 hours a day, even when switched off! These are called “phantom loads”, and taken together, keep an inverter turned on and waste a lot of power if not remedied.
The cure is to have lots of wall switches to shut off power to outlets. This is easier than actually pulling the plugs every time. The stereo and TV and much of your office equipment should use switched outlets to disconnect at night, or whenever not used. In houses without such wall switches, the extension cord/outlet strip with built in on/off switch is an easy way to disconnect phantom loads.