Residential Energy Usage
Renewable Energy System Sizing Calculator

Here is a place to enter items commonly used in a residence which require electricity to operate. Each item has a space for the watts it requires and the approximate hours per day (HPD) the item is turned on.

Living Room

Den

Bedroom 1

Bedroom 2

Bedroom 3

Bedroom 4

TV, Large Stereo and Satellite HPD:
Night Lighting Watts: HPD:

Kitchen

Ceiling Lighting Watts: HPD: Sink Light: HPD: Vent Hood Light: HPD:
Accent Lighting Watts: HPD: Entertainment Systems, please select: None TV Small Stereo TV and Satellite (Dish or DirecTV) Large Stereo TV and Large Stereo TV, Small Stereo and Satellite TV, Large Stereo and Satellite HPD:
Night Lighting Watts: HPD:

Laundry Lighting

Ceiling Lighting Watts: HPD: Sink Light: HPD:
Night Lighting Watts: HPD:

Appliances

Refrigerators are probably one of the the biggest power users in a residence. One reason for this is because they aren't all that energy efficient, and they must be run 24 hours a day. Over time, that is a lot of energy used. When figuring the load for a refrigerator or freezer, generally the watts will be variable, and dependent on how energy efficient it is. Also, the duty cycle, or how long it runs opposed to how long it doesn't over the course of an hour, is dependent on efficiency of a particular model. For reference and generalities, use 200 watts and 12 hours per day, which equates to a 50% duty cycle(12 hours out of 24) at 200 watts.
Refrigerator 1 Watts:, HPD:, Refrigerator 2 Watts:, HPD:
Freezers are generally a bit more efficient than refrigerators and use less energy and usually run on less than a 50% duty cycle unless they are older models.
For freezers, use 150 watts and use 50% duty cycle. Actual usage can be determined using specialized equipment.
Freezer Watts:HPD:
The energy usage for other appliances can be determined by using the wattage of the item, times the number of hours per day it runs. To get an accurate determination for this calculator, on washers, dryers (YOW!) and dishwashers (YOW!), take the number of loads done per week and divide that by 7 to get the average hours per day and enter that amount for the HPD on each item.
Washer Watts:, HPD:
Dryers are generally not a good idea on systems that are completely disconnected from the grid simply because they require so much energy that the battery bank, inverter size and wiring must be extreme to accomodate a dryer. It is included here for informational purposes. Run the calculator and include the dryer and then just take out the dryer and see the difference. Dryer Watts:, HPD:
Dishwasher Watts:, HPD:
Microwave ovens are generally used for heating leftovers and the occasional frozen dinner. They are seldom used for major cooking. Since they are used in such short time spans, just try to estimate usage over the course of a week and enter the values here. Many smaller microwave ovens are about 450 watts and larger ones up to 1200 watts. Likely, unless major cooking is done in a microwave oven, the time and wattage they use is very little over a week's time, but the inverter must be able to carry it when it is actually used.
Microwave Oven Watts:, HPD:
Other appliances like electric skillets and toaster ovens are along the same lines as a dryer in that they are not really recommended for a completely off-grid home. In the spaces below, enter these miscellaneous items and how much time per day they are used. If they are only used once or twice per week, take the hours it is used in a week's time and divide that by 7 to get the average hours per day it is used. Remember, the inverter must be able to carry these loads.
Miscellaneous 1 Watts: Computer Hair Dryer Coffee pot Electric skillet Blender Toaster Mixer Crock Pot Bread Machine Large Electric Deep Fryer , HPD:
Miscellaneous 2 Watts: Computer Hair Dryer Coffee pot Electric skillet Blender Toaster Mixer Crock Pot Bread Machine Large Electric Deep Fryer , HPD:
Miscellaneous 3 Watts: Computer Hair Dryer Coffee pot Electric skillet Blender Toaster Mixer Crock Pot Bread Machine Large Electric Deep Fryer , HPD:
Miscellaneous 4 Watts: Computer Hair Dryer Coffee pot Electric skillet Blender Toaster Mixer Crock Pot Bread Machine Large Electric Deep Fryer , HPD:

Heating and Air Conditioning

Whew! Where to start! On a completely renewabe-energy powered home, air conditioning and all-electric heating are crazy power-hungry.
Looking at the heating element for an all-electric heater for a home, and not a particularly large one at that, it was noted that the wattage rating for just that element was 4500 WATTS! So, assuming there is just one of these in the residence, along with the blower to move the air through the ductwork, an estimate of an additional 500watts for the blower will be added and call it an even 5000 watts. Now lets say that the residence is reasobnably efficient and this heater runs 50% as it cycles on and off over a 24-hour period. So that would be 12 hours per day at 5000 watts. That is 60KWH per day just for this!
Do you *really* want to do this? Unless you are going to be a completely renewable-powered home, with this situation, it might be better to leave the high-power items on-grid and let the renewable system take care of everything else. It is not impossible, but run the calculator with and without just these high-power items and see how it comes out.
Now, figure an A/C unit. Even use an energy-efficient model that is a 3 ton unit. It draws 1100 watts for the compressor and an additional 500 watts for the blower for a total of 1600 watts. Again use a 50% duty-cyce over a 24-hour period so that would be 19.2 KWH per day just for this! If the unit is a heat pump, use this number for heating as well since it will be close except for when the "extreme heat" is on (the element strips are energized, usually below 32 degrees outside or when there is as little as a 3 or 4 degree difference between the thermostat setting with the room temperature being the lower one, depending on the thermostat.)
Again, do you *really* want to do this?
To figure these in, enter the values in the spaces provided. Leave them blank if usage is unknown. For an estimate, and to see how much more system is needed to add these, use the numbers from above and 12 hours per day. These numbers will vary greatly due to efficiency, sizing, comfort preferences and many other factors, and are included here for reference only unless there is an accurately established usage figure for the unit in use.
All-electric heater: HPD:. Heat-pump or air conditioner: HPD:.

"Phantom Loads"

Phantom loads are loads created by items such as alarm clocks, cordless phones, any device that has a remote control, computers (when they are "off") and anything else that continuously draws power just by being plugged in. These loads are generaly very small, but added together, they can add up to a sizable amount of watts and could mean more power is needed from the renewable energy system, meaning much more cost, with very little gain. Some of these items can be eliminated for a great savings in system requirements. Use battery-powered alarm clocks where possible. TV's VCR's. satellite recievers, stereo systems and anything else that is remote controlled, (and many that are not) draw some power even if they are "off". These items can be plugged into power strips and turned off there when they are not being used. It will mean a few extra steps to turn on the ower strip, but once that is done, the remote control will operate as usual. Just remember to turn the strip back off after using these items.
To figure phantom loads, there are two types and therefore two different values to be used. The first is the "small" phantom loads. Things like alarm clocks, cordless phones, and just about any device that uses a "wall wart" or one of those little (usually black) boxes that plugs into an outlet and has a small cord going to the device. Remember to include microwave ovens (this is a different type of load from the entries above) and regular oven timers if they are plugged in.
Count the number of devices in this category and multiply by 5 and enter the result here. Watts:
Large phantom loads are the other items like TV's, Stereos, Satellite Receivers, and computers (only the times they are "off" but plugged in), VCRs and DVD players. For these devices, count the number of devices in this category and multiply by 10 and enter the result here. Watts:.
Remember, these may be the same devices as listed above in other areas but those values are for the devices when they are "on". These are their loads when they are "off".
Once all information has been entered into this form, press the "Study It!" button below to continue to learn how much power is actually used.

Renewable Energy and System Sizing Calculator