A solar module is a photovoltaic device consisting of a number of “cells”. These cells are connected electrically, laminated, encapsulated and packaged into a frame. The common name for these is “solar panel”.

The rating for solar panels has been climbing steadily over the years. Ten years ago, solar panels were in the 120-175 watt range, where today panels usually are in the 220-250 watt range.

When selecting modules for a string inverter, it is important to consider module “tolerance” which is expressed in a (+/-) percentage compared to nameplate rating. A set of modules with bad tolerances will play an important role in performance inefficiencies. Wide tolerances do not affect the production efficiencies of micro-inverters as significantly.

Solar panels are available in two major types:

Monocrystalline

Monocrystalline modules are slightly more expensive and slightly more efficient due to the purity of the silicon used in production. They are identifiable by the distinct octagon shapes visible on the surface of the panel.

Polycrystalline

Polycrystalline modules are more uniform in appearance, have square corners and appear to be one color (blue), though some cells may be darker toned.

Standard Efficiency vs. High Efficiency

As a rule of thumb, you need 100 square feet for roof space for every 1000 watts of photovoltaic modules. If you are using high efficiency modules you can reduce this space to 80 feet square. Therefore high efficiency modules use 20% less roof space to produce the same amount of power. Said another way, high efficiency modules are 20% more powerful. This explanation is often used by unscrupulous sales people to sell an expensive product.

Here is why:

A 230 watt standard efficiency panel produces the same 230 watts as a high efficiency panel.
The yearly energy harvest from some standard efficiency panels is higher than some high efficiency panels.

As a custom solar system designer and installer we will explore your options and recommend high efficiency panels where they make sense. In most cases, we feel that the only thing efficient about a high efficiency panel module is the rate at which money is removed from a client’s checking account.

An inexpensive standard efficiency module on a microinverter system usually outperforms high efficiency modules on a string inverter. Continue reading below for more detailed information.

Are “High Efficiency” Modules Really “Highly Efficient”?

Case A

Would you want to pay for power you won’t receive? A certain manufacturer of expensive “high efficiency solar systems” produces a panel with a 230 watt (+5/-5%) tolerance. Ten modules are wired together in a “string“ series and tied into a PV inverter.

230 watts x 10 modules = 2300 watts. Factor in the -5%. The low number always wins in PV.
230 watts x -5% = 2185 watts.

This shows 115 watts of PV power paid for and not realized. Consumers need to be aware that if they are paying $5.50 per watt x 115 watts = $632.50 for power they are not getting. 2300 watts x $5.50 watt = $12,650.00 price of system installed.

Case B

A lower priced “standard efficiency” solar panel produces a 230 watt with a (-0/+3)% tolerance.
10 modules are wired together to a string inverter

230 watts x 10 = 2300 watts, with no power lost due to module mismatch.

Here is the topper - a standard efficiency system operates more efficiently than the high efficiency system and costs less!
2300 watt x $4.50 watt = $10,350.00

Let Cantiague Electric install a true lower cost, high efficiency system for your home or business. Contact Us Today!