DIY Guide to Running Appliances on Solar Power

The demand for solar power continues to increase around the world. Governments and individuals recognize the need for renewable energy and its advantages over fossil fuels are aplenty. The question for homes and RV owners however, is still the same. How many solar panels do I need to run appliances?

The average American home uses 900kwh per month or 30kwh/day, which is equal to 25-35 250W solar panels. The solar panel’s rating and how appliances are used determine the total monthly wattage consumption. RV monthly power consumption is much lower though, and solar powered homes use power conservatively.

How to Calculate Appliances Power Consumption

There are charts and tables here you can use for guidance. You may skip to those if you want, but it is important that you learn how to calculate appliances wattage consumption. Homes and RVs use appliances in different ways so you have to figure out your total power usage.

To find your monthly electrical consumption, check your electric bill. That alone should give you an idea of how many solar panels you will need. You can also use a power usage monitor to keep track of appliances’ power consumption.

The third method is to check the watts of each appliance (it will be in the power cord), write them down and add the wattage total. This takes more time, but it’s ideal if you want to limit the number of running appliances when you switch to solar.

How to Calculate Appliance Power Use in Specific Time Periods

Now you have to calculate how many hours per day an appliance runs. A 100W stereo running for 2 hours day uses 200W (100W x 2 hours = 200W). A 1000W microwave that runs for 10 minutes a day on the other hand, consumes only 100W.

Remember, appliance wattage is measured in watt/hour. Multiply watt hour x number of hours used for appliances that run more than an hour. For those that run for less than an hour, divide into minutes.

Some appliances and tools have starting / peak watts and running watts. Running watts is how much power the appliance / tool uses operating continuously. Peak or starting watts is the amount of power required during startup. Peak / surge watts is higher than running watts.

Refrigerators with freezers typically need 2200 starting watts and 700W running. Air conditioners need anywhere from 1800W to 6800W depending on the size. Here is a table showing various appliances and tools with running and peak watts.

Appliances with Starting and Running Watts

Appliance	Starting/Peak/Surge Watts	Running Watts
Refrigerator	2200	700
1/3 HP Water Well Pump	2000	1000
1/2 HP Sump Pump	2200	1000
1/2 HP Furnace Fan Blower	2350	800
Window AC 10,000 BTU	1800	1200
Central AC 10,000 BTU	3000	1500
Heat Pump	4700	4500
Washign Machine	2300	1200
Electric Clothes Dryer	5400	1400
Inflator Pump	150	50

Make sure you include peak / surge watts in your calculations. A fridge may only use 700W running, but it needs those 2000W to get started. Include that wattage when determining how many solar panels you will use.

Kitchen Appliances Solar Power Needs

Appliance	Watt Hour	Power Consumption
Blender	200W	36W / 12 min a day
Coffee Machine	500W-1000W	160W-320W / 10 min a day
Electric Oven	2000W-2500W	250W-500W / 10 min a day
Dishwasher	1200W	1200W / 1hr a day
Microwave	800W-1500W	150W-300W / 10-12 min a day
Toaster	1200W	120W / 10 min a day
Refrigerator	150W – 200W running	1000W / day

Laundry Appliances Solar Power Needs

Appliance	Watt Hour	Power Consumption
Washing Machine	3000W	12000W / 4 hours a week
Ceiling Fan	1200W	6000W / 5 hours a week
Vacuum Cleaner	800W	1600W / 2 hours a week
Iron	1000W	5000W / 5 hours a week
Tumble Dryer	3000W	6000W / 2 hours a week
LED Bulb	7W	42W / 6 hours a week
Hot Water Immersion Heater	3000W	9000W / 3 hours a week

Living Room Appliances Solar Power Needs

Appliance	Watt Hour	Power Consumption
LCD TV	250W	1000W / 4 hours a day
Video Game Console	180W	360W / 2 hours a day
Small Window AC	600W running watts	3600W / 6 hours a day
Stereo System	40W	160W / 4 hours a day
Energy Efficient Light	12W	60W / 5 hours a day

Bedroom Appliances Solar Power Needs

Appliance	Watt Hour	Power Consumption
TV	150W	450W / 3 hours a day
Ceiling Fan	25W	225W / 9 hours a day
Desktop Computer	100W	500W / 5 hours a day
Air Conditioner	1000W	5000W / 5 hours a day
Mobile Phone / Tablet Chargeer	5W	15W / 3 hours a day
Desk Fan	10W	20W / 2 hours a day

How Many Solar Panels Do You Need?

As we stated earlier, 20-30 solar panels can produce 900-1000kwh per month, the average power consumption of an American home. But the number you need will also depend on a lot of factors.

First is the solar panel rating. A 200 watt solar panel like the Rich Solar 2 Pack can produce 1000W a day under ideal conditions. 30 of these generate 30000W or 30kwh a day. That’s 900kwh a month.

The calculation formula is the same no matter the solar panel size. Of course if you install a larger solar panel, it will produce more power and you’ll need a smaller array. A 400W solar panel could produce 2000W every day. 15 of these gets you to 30kwh a day / 900kwh a month.

Note that solar panels may not always reach peak output. In real world situations it can happen that solar panels to reach 200 watts or whatever their rated output is. Even if it did we have to account for energy losses in cable and solar panel transfer, inverter losses etc. An 80%-85% efficiency is what you can really expect.

Do You Need Solar Batteries?

In a word, yes, you need a battery. The more appliances you use, the more batteries you will need. Your usage determines how many will be required.

Let’s start with the basics. A battery functions as a storage for solar energy. Their capacity is measured in amp hours (ah) or watt hours (wh). Once your solar panels are installed, it collect energy from the sun. Without a battery, the energy goes straight into your appliances. Sounds good right? Well, not quite.

There are two problems here. First, you won’t be able to run these appliances at night. No sun, no solar power to run these devices. Second, solar panel performance will dip when it’s overcast or raining. If it rains for several days or winter sets in, solar panels won’t be as efficient no matter the size.

A battery solves both problems. Extra solar power is stored so you can keep the lights on at night. Second, the stored energy will be your primary power source during winter and rainy days.

Solar Battery Bank Sizing – How Many Batteries You Need

Solar batteries can be stacked together, known as a battery bank, to provide more power. A good sized battery bank and solar array (solar panels linked together) can supply the required power. The number of batteries you’ll need depends on the following.

How many days you want to use the batteries before recharging. Depth of discharge (DOD) tells you how long you can use a battery before it needs to be recharged. Lithium batteries like the Battle Born 100ah have up to 90% DOD, meaning you can use it till it is almost empty. Lead acid batteries have a 50% DOD, so you can only utilize half the capacity.

If you have to run appliances for a specific number of hours / days, you must make sure there is sufficient charge in the battery left. Knowing how much power all your appliances use is necessary to find the right battery bank size.

Voltage power of your solar system. The general rule is your solar array must be larger than the battery capacity. A 48V solar system should have a 36V battery bank, a 36V solar system should have a 12V battery bank etc. This allows the battery to cope with voltage drops and spikes, energy loss and fluctuations in power.

The larger the battery capacity, the more appliances you can run. To find out how much capacity a battery has, multiply amp hours x volts / 100 = watt hours.

400ah x 24V = 9600 / 100 = 96 watt hours.

So a 100% charged, 400ah 24V battery can run an appliance or appliances for 96 hours. Once you know how many watt hours you use, it’s easy to figure out the battery capacity needed. Because lithium ion batteries have a higher capacity, they are superior to lead acid.

Grid Tied vs. Off Grid vs. Hybrid Solar Systems – Which is Better For Appliances?

These are the three major kinds of solar systems used today. Your power consumption, preference, and lifestyle determines which is best.

Grid Tied Systems

A grid tied or on grid system is the most common setup for solar powered homes and business establishments. A grid tied system has solar panels but does not require batteries. The home / establishment is connected to an electric grid.

Extra power produced by your solar system goes into the electric grid, and you receive credit for it. Grid tied homes have access to electrical and solar power. However they cannot produce electricity in case of a power outage.

Off Grid Systems

Living off the grid means exactly that, your home or RV is not linked to any electric power grid. You solar system must have enough solar panels, batteries and inverters to meet your daily power requirements. It’s more expensive than a grid tied system, but you won’t be affected by blackouts and you don’t have to pay any monthly bills.

Most off grid systems have a solar generator or another backup power source. They are often used to power refrigerators, ACs, air compressors and other appliances that would take up the solar system’s resources.

Hybrid Solar Systems

Hybrid solar systems provide solar panel power and battery storage. A hybrid system can be hooked up to a power grid but still use a battery for extra power. They use solar panels in the morning and the battery in the evenings. When the battery reserve is gone, they use the grid while waiting for the battery to recharge.

Tips to Save on Solar Power

There are many ways to save energy be it at home or in an RV. The following are some of the things you can do to reduce energy use.

• Use only appliances you need. Sounds simple, but once you make the move to solar and need to save energy, you’d be surprised how many of these appliances/devices/tools you can do without.
• Turn off appliances you don’t use. The lights, computer, fan, AC, boat fridge, everything. If it’s not in use, shut it off.
• Ensure your solar panels are not being obstructed. Foliage, branches, birds’ nests etc. Any of these can keep the system from drawing energy.
• Use energy efficient appliances.
• For RV owners, you can use camping utilities instead of regular kitchen appliances. They should meet your needs while consuming less power.
• Keep your solar panels clean. You can do it yourself or call a solar cleaning service.

Conclusion

It’s easy to see why a lot of people want to try solar power. It’s clean, renewable and dependable. Many however, get frustrated because they don’t know how much solar power they will need. Hopefully the tips included in this guide was able to help you.