Filling out a Load Chart

"I want a solar power system for my motorhome" said the customer.
"What do you want to run"? I asked.
"Everything" he replied.
"What is an Everything"? I queried. "Can I buy one in the local electrical store?"
"What does it do when I get it"?

Actually I didn't say that at all, I respect you folk more than that! This question is however asked with monotonous regularity.

Without some idea of what you actually want to run with your solar system you are unfortunately wasting everyone's time. Start by ruling out everything that uses continuous heat. This means electric stoves (except microwaves), electric hot water and electric room heating and cooling. Forget your air conditioner and fan heater (except for very brief periods). Forget asking your solar dealer to do your designing. No excuses folk you must get at least some idea of what you personally want to power. Without coming to terms with this basic concept your solar system will quite possibly not work they way you hope!

Consider what really need ...

You need to become an electrical sleuth! This means starting to look at every electrical appliance you can lay your hands on and discovering its electrical consumption. Just about everything on the market today has an electrical placard on it stating the power consumption. This may be in watts or it may be in amps. To get the wattage remember Georg Ohm and his rule: Amps x voltage (of appliance) = watts.

Make a load chart!

You need to make a list. The shorter it is the less your solar system will cost you. You need to fill out a chart. We have designed a simple chart for you to print out and then fill in.
Click here to get a load chart ... Print one!

In becoming an electrical sleuth you are working out what an appliance costs to run in terms of energy. This will be either expressed in watts or as a current and a voltage. Virtually all modern electrical appliances will have this printed on them in the form of a placard. The wattage figure is what you are after. If the appliance placard states a voltage and a current you can convert this to watts by the sum: Voltage x current = wattage. (Ohms law)

Lets look at a few appliances:

• Lighting: This is high on the priority list. Seeing in the dark is all important. How many lights, how long for and what is the wattage of each bulb?

• Television: Most folk have one. Mine is rated at 90 watts with an average load of 60.

• Video and Stereo: Not to huge a power consumer , most are under 20 watts.

• Microwave: You will need a largish inverter for one of these. Could use 1500 watts or more. Don't go on the cooking rating, this will be different from the power consumption. Find the placard!

• Toaster and Kettle: I have both. While they use a large amount of electricity they are usually only used for a short time .

• Refrigerator: Very opinionated subject for solar buffs ... We have a page on refrigeration in this information section.

How to fill in the chart ...

You have printed one out haven't you?

1. List your appliances down the left hand column. It may be easier if you divide this column into rooms if you are planning a household load sheet.

2. List the appliance wattage in the watts column. Remember the formula current x voltage if all you have is current data.

3. Determine the average daily run time of the appliance in hours. For items that may only be used once a week or so, work out the weekly wattage and divide by seven

4. Calculate the watts per day then tally up the total foe your electrical load.

5. Divide this by 0.7. This gives a factored amount and will allow for inefficiencies etc. in your power system.

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