Photovoltaic Tutorial:

Step-By-Step Guide to Going Solar

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10. Prepare a budget and shop for equipment.

Once you know the sizes and other specs of the equipment you need, it's time to shop for products that will best fit the bill. If you've never been through a solar installation before, it may be prudent to delay the actual purchases until your construction permit application is approved. That way you can avoid having to exchange or return merchandise. (BEWARE: For many suppliers, all sales are final.) If you plan to hire a contractor to install your PV system, you should likewise touch base with him or her before placing an order. In fact, the more qualified, knowlegeable people you talk to in advance, the better. All this advice and intel should inevitably lead to an efficient design, the selection of quality components, the best available price, and the fewest mistakes.

Of course, you can't apply for the permit until you know the makes, models and sizes of your primary components, smaller devices, wire, conduit and other supplies. By preparing an itemized equipment budget, you'll kill two birds with one stone. First, a typed budget allows you to compile all the item info you need typed clearly on one easy-to-reference sheet. Second, you'll know how much it's all going to cost.


Sample budget prepared by the author for a 4.5k (STC/DC) grid-tied PV system with no battery backup. A spreadsheet program allows you to insert or delete items, as well as change items, quantities and prices. Each time, the total column automatically updates. The "4K" mentioned in the title refers to the AC power output of the inverter.

Besides your two main objectives, you can do three other things with this document:

Any PC or MAC spreadsheet software will work for preparing a budget. Only two math functions are required, sum and multiplication, so you don't need to be an expert bean counter. Here's a cheat sheet for Excel from the University of Chicago IT dept.

After you've chosen a make and model (or size) for each component, find the lowest price available and use that figure in your budget. Some of the more popular online suppliers with low prices include Wholesale Solar, Civic Solar, Affordable Solar and Solar Electric Supply. All these sellers generally do business in both a retail mode and as a wholesaler.

For wire and conduit, you'll probably need to shop at local electrical suppliers to get the best prices. That's because shipping charges charged by online suppliers can jack up the cost substantially. Of course, you can still include wire and conduit in any request for a bid. The company may be willing to fetch the supplies you need from a nearby electrical supplier, then throw it onto the same truck that's hauling your modules, racking and other equipment. The extra weight won't add appreciably to the freight charge, and you can (hopefully) get charged at the solar company's discounted rates.

Getting a purchase order

Once you choose your supplier(s), it's highly recommended that you ask for an official purchase order (on the company letterhead) before submitting any payment. Since you're spending about $10,000, this really isn't too much to ask, even from an online store. The purchase order should itemize all the components and hardware, their quantities and prices. For major items like the array modules, the inverter and racking, ask the company to specify the warranty period on the invoice.

This is important, because suppliers sometimes sell a different warranty than the one published by the manufacturer in its product literature. Since many rebates and AHJ's require specific time periods on solar products and service (usually 10 years), you may end up having to buy an extended warranty if that period isn't covered in the purchase. And that adds up to a lot of money.


The UL rating in the bottom left corner of this module label lets a building inspector know that the product will perform to code.

In addition, ask for language on the purchase order that says something to the effect: "All electrical devices, wire and other appropriate products are UL listed and properly labeled as required by the NEC." (See photo above.) Building inspectors won't approve any installation if the equipment and wire aren't marked.

Finally, before submitting a payment, find out the supplier's policy for returning defective, incorrect or unneeded merchandise. You should also know in advance who's responsible for return shipping costs, deadlines and restocking fees that apply to your purchase.

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Continued on Page 11... (Apply for a building permit.)

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