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You can learn about everything from home efficiency to how to install a photovoltaic system from our classes, articles and educational videos. If you're looking to become a well informed consumer, a professional installer or just to explore solar energy, we have a resource that can help!

You'll find:

Hands-on workshops and classes for homeowners and professional installers
Educational Videos you can watch online and access in the future
Free solar energy video tips
A large library of articles on various topics about solar energy, a thorough glossary and calculators to help you design your system.

How Solar Panel Make Power from the Sun
How It's Made - Solar Panels
DIY Solar Panel Training PV Photovoltaic
Solar Panel DIY Wiring Configurations Solar Power
Solar Power DIY Kit
How to Calculate and Size Solar Power?
Recommended Design Practice of Off Grid Solar PV Systems

The design process is a fairly simple and straight forward that doesn’t require a lot of technical knowledge.

The intial steps are:
Determine the load in energy for a 24-hour period. Not the watts, but the watt-hours.
Determine the size of the solar array to be used.
Determine the battery size.

Design Example
The following example is a rough estimate to take to a system designer to discuss cost and objectives. He/she will then fine tune the system based on actual components, cable distance, etc… Our basic objective in this simple example is to provide power to a 250 load (light bulb) for 24 hours per day in two different cities (Klang Valley and Tasmania) with 90 % availability. Thiis is a system we have designed many times using remote cell radio sites. The transmitter is continuous 250 load, and the system will be a typical sized system that can be used in a home application. The only difference is radio sites are designed for 99.99% availability and this one will only be 90%. Getting from 90 to 99.99% greatly increases the cost with a larger solar array, larger batteries, and a standby generator set.

Step 1: Design for Worst Case
In this example the worst case is simple to determine because the load is continuous 24 x 7 x 365 of a 250 watt light bulb. So the worst case is the month of December and January when the Solar Insolation is at its lowest point. In some instance, the worst case for the load is the summer and worst case for the resource is the winter, requiring you to perform two designs and then to select the one system that will carry the load through both summer and winter.

So in this example we need to determine the energy needed in a 24 hour period. This is done with watt-hours. To determine the watt-hours is straight forward of Watts x Time (in hours). So 250 watts x 24 hours = 6000 watt-hours or 6 Kwh in a day or 24 hours. Make note of this number as it will be needed latter.

Step 2: Throw in a Fudge Factor
You multiply the total 24 hour load energy by 1.5 to account for several factors that would be handled individually in a detailed design. Some of the factors accounted for by this method are all the system efficiencies, including wiring and interconnection losses as well as the efficiency of the battery charging and discharging cycle, and allowing extra capacity for the PV system to recharge the batteries after they have been drained to keep the load going in bad weather. So 6000 x 1.5 = 9000 watts or 9 Kwh. Now take note of this figure.

Step 3: Determine Solar Insolation in Hours
(Click to zoom the map)
Most solar map data are given in terms of energy per surface area per day. No matter the original unit used, it can be converted into kWh/m2/day. Because of a few convenient factors, this can be read directly as "Sun Hour Day” The number you want to use in this example is for December since December days are the shortest. Klang Valley is shown to receive 4.6 kWh/m2/day in December.. For Tasmania, the number is 1.2 Kwh/m2/day. So we need to note 4.6 and 1.2 for our Sun Hour Day as it will be used to determine the solar panel array wattage.

To forecast accurately, please see Malaysia Weather Historical & Forecast Data.

Step 4: Determine The Size of the Solar Panel Array
The size of the solar panel array is determined by the adjusted daily energy requirement using the Fudge factor number divided by the sun-hours per day. So for Klang Valley 9000 / 4.6 = 1956 watts, round up to 2000 watts. For Tasmania 9000 / 1.2 = 7500 watts. Note the huge difference; it is because of the Solar Insolation. Location matters and will greatly affect system cost.

Step 5: Determine Battery Size
All batteries will last substantially longer if they are shallow cycled. That means discharged only by about 20% of their capacity in a given day. Where as deep discharge or cycling means that a battery is discharged by as much as 80% of its capacity. A conservative design of 90% availability will save the deep cycling for occasional duty like several cloudy days in a row. This implies that the capacity of the battery should be about five times the daily load. So that means the capacity should be 5 times the daily load.

To figure the daily load, go back to the original load number before the fudge factor—that is, 6000 watt hours. Add to this a battery fudge factor of about 50% to account for the efficiency of the battery discharge, the fact that only 80% of the battery's capacity is available, and the loss in efficiency because PV systems rarely operate at the battery design temperature.

The end result is that the battery design load is 6000 times 1.5 or 9000 watt hours, which is coincidentally the same as the array's design load, but for different reasons. This is the daily energy taken from the battery, which is now multiplied by five to ensure 20% daily discharge: 9000 x 5 = 45,000 watt hours. This is the battery capacity, which is usually given in ampere-hours so it must be divided by the system voltage; 45,000 / 12 = 3750 Amp Hours. Take note this example is a 12 volt system. If you were using a 24 volt system the battery capacity would be 45,000 / 24 = 1875 Amp Hours. To put this into perspective a 3750 AH battery bank would weight a few tone and the size of a china cabinet or a very large office desk. The floor of this would need to be reinforced concrete built to 3000 psi test.

That’s about it to get you in the ball park. The system designer will then determine the inverter and charge controller requirements and fine tune the system numbers. In this example a 500 watt inverter (2 x Max Load = 2 x 250 = 500) and an MPPT controller of 175 amps for the Klang Valley system, and 650 amps for Tasmania.

Solar Panel Wire And Voltage Drop Calculate

How to Size Wiring for Your System

Properly sized wire can make the difference between inadequate and full charging of a battery system, between dim and bright lights, and between feeble and full performance of tools and appliances. Designers of low voltage power circuits are often unaware of the implications of voltage drop and wire size.

In conventional home electrical systems (120/240 volts ac), wire is sized primarily for safe amperage carrying capacity (ampacity). The overriding concern is fire safety. In low voltage systems (12, 24, 48VDC) the overriding concern is power loss. Wire must not be sized merely for the ampacity, because there is less tolerance for voltage drop (except for very short runs). For example, at a constant wattage load, a 1V drop from 12V causes 10 times the power loss of a 1V drop from 120V.

Universal Wire Sizing Chart
A 2-Step Process

This chart works for any voltage or voltage drop, American (AWG) or metric (mm2) sizing. It applies to typical DC circuits and to some simple AC circuits (single-phase AC with resistive loads, not motor loads, power factor = 1.0, line reactance negligible).

STEP 1: Calculate the Following:

VDI = (AMPS x FEET)/(%VOLT DROP x VOLTAGE)

VDI = Voltage Drop Index (a reference number based on resistance of wire)
FEET = ONE-WAY wiring distance (1 meter = 3.28 feet)
%VOLT DROP = Your choice of acceptable voltage drop (example: use 3 for 3%)

STEP 2: Determine Appropriate Wire Size from Chart

Compare your calculated VDI with the VDI in the chart to determine the closest wire size. Amps must not exceed the AMPACITY indicated for the wire size.

Wire Size	Area mm2	COPPER		ALUMINUM
AWG	Area mm2	VDI	Ampacity	VDI	Ampacity
16	1.31	1	10	Not Recommended
14	2.08	2	15
12	3.31	3	20
10	5.26	5	30
8	8.37	8	55
6	13.3	12	75
4	21.1	20	95
2	33.6	31	130	20	100
0	53.5	49	170	31	132
00	67.4	62	195	39	150
000	85.0	78	225	49	175
0000	107	99	260	62	205

Metric Size by cross-sectional area	COPPER (VDI x 1.1 = mm2)	ALUMINUM (VDI x 1.7 = mm2)
Available Sizes: 1 1.5 2.5 4 6 10 16 25 35 50 70 95 120 mm2

EXAMPLE: 20 Amp load at 24V over a distance of 100 feet with 3% max. voltage drop
VDI = (20x100)/(3x24) = 27.78	For copper wire, the nearest VDI=31. This indicates #2 AWG wire or 35mm2

NOTES: AWG=Amercan Wire Gauge. Ampacity is based on the National Electrical Code (USA) for 30 degrees C (85 degrees F) ambient air temperature, for no more than three insulated conductors in raceway in freee air of cable types AC, NM, NMC and SE; and conductor insulation types TA, TBS, SA, AVB, SIS, RHH, THHN and XHHW. For other conditions, refer to National Electric Code or an engineering handbook.

Use the following chart as your primary tool in solving wire sizing problems. It replaces many pages of older sizing charts. You can apply it to any working voltage, at any percent voltage drop.

Determining tolerable voltage drop for various electrical loads

A general rule is to size the wire for approximately 2 or 3% drop at typical load. When that turns out to be very expensive, consider some of the following advice. Different electrical circuits have different tolerances for voltage drop.

LIGHTING CIRCUITS, INCANDESCENT AND QUARTZ HALOGEN (QH): Don't cheat on these! A 5% voltage drop causes an approximate 10% loss in light output. This is because the bulb not only receives less power, but the cooler filament drops from white-hot towards red-hot, emitting much less visible light.

LIGHTING CIRCUITS, FLUORESCENT: Voltage drop causes a nearly proportional drop in light output. Flourescents use 1/2 to 1/3 the current of incandescent or QH bulbs for the same light output, so they can use smaller wire. We advocate use of quality fluorescent lights. Buzz, flicker and poor color rendition are eliminated in most of today's compact fluorescents, electronic ballasts and warm or full spectrum tubes.

DC MOTORS may be used in renewable energy systems, especially for water pumps. They operate at 10-50% higher efficiencies than AC motors, and eliminate the costs and losses associated with inverters. DC motors do NOT have excessive power surge demands when starting, unlike AC induction motors. Voltage drop during the starting surge simply results in a "soft start".

AC INDUCTION MOTORS are commonly found in large power tools, appliances and well pumps. They exhibit very high surge demands when starting. Significant voltage drop in these circuits may cause failure to start and possible motor damage. Follow the National Electrical Code. In the case of a well pump, follow the manufacturer's instructions.

PV-DIRECT SOLAR WATER PUMP circuits should be sized not for the nominal voltage (ie. 24V) but for the actual working voltage (in that case approximately 34V). Without a battery to hold the voltage down, the working voltage will be around the peak power point voltage of the PV array.

PV BATTERY CHARGING CIRCUITS are critical because voltage drop can cause a disproportionate loss of charge current. To charge a battery, a generating device must apply a higher voltage than already exists within the battery. That's why most PV modules are made for 16-18V peak power point. A voltage drop greater than 5% will reduce this necessary voltage difference, and can reduce charge current to the battery by a much greater percentage. Our general recommendation here is to size for a 2-3% voltage drop. If you think that the PV array may be expanded in the future, size the wire for future expansion. Your customer will appreciate that when it comes time to add to the array.

WIND GENERATOR CIRCUITS: At most locations, a wind generator produces its full rated current only during occasional windstorms or gusts. If wire sized for low loss is large and very expensive, you may consider sizing for a voltage drop as high as 10% at the rated current. That loss will only occur occasionally, when energy is most abundant. Consult the wind system's instruction manual.

More techniques for cost reduction

ALUMINUM WIRE may be more economical than copper for some main lines. Power companies use it because it is cheaper than copper and lighter in weight, even though a larger size must be used. It is safe when installed to code with AL-rated terminals. You may wish to consider it for long, expensive runs of #2 or larger. The cost difference fluctuates with the metals market. It is stiff and hard to bend, and not rated for submersible pumps.

HIGH VOLTAGE PV MODULES: Consider using higher voltage modules and a MPPT solar charge controller to down convert to the system voltage (e.g. 12, 24 and 48V) to compensate for excessive voltage drop. In some cases of long distance, the increased module cost may be lower than the cost of larger wire.

SOLAR TRACKING: Use a solar tracker (e.g. Zomeworks or Unirac) so that a smaller array can be used, particularly in high summer-use situations (tracking gains the most energy in summer when the sun takes the longest arc through the sky). The smaller PV array will require smaller wire.

WATER WELL PUMPS: Consider a slow-pumping, low power system with a storage tank to accumulate water. This reduces both wire and pipe sizes where long lifts or runs are involved. A PV array-direct pumping system may eliminate a long wire run by using a separate PV array located close to the pump. Many of our solar water pumps are highly efficient DC pumps that are available up to 48V. We also make AC versions and converters to allow use of AC transmitted over great distances. These pumps draw less running current, and far less starting current than conventional AC pumps, thus greatly reducing wire size requirements.