How do I compare a proposal from Solaflect with one from another solar installer?

The tradition in the solar industry is to compare system costs according to their “cost per watt” of capacity. “Capacity” is the ability of the solar panels to produce a certain amount of electricity when exposed to light. More specifically, it is a measure of how much electricity the panels will create when they are at a specific temperature and are exposed to light of a specific intensity. For example, a solar array rated at 4 kilowatts (kW) will produce 4 kW of direct current electricity under standardized conditions. The amount of electricity created by the panels will vary if the temperature or intensity of light change.

(Before going further, it may help to understand the difference between a kilowatt and a kilowatt-hour.)

If you are comparing one installer’s proposal to put solar on your roof against another installer’s proposal to put solar on your roof, then comparing cost-per-watt is perfectly reasonable, as long as both installers are going to use similar quality equipment.

However, the Solaflect PV Tracker is qualitatively different from usual fixed-mount solar arrays. The advantage of the Tracker is precisely that it uses its solar panel capacity more effectively than do fixed-mount arrays. In particular, the Tracker ensures that the panels receive more intensity of light, because it keeps the panels facing directly at the sun at all times. Meanwhile solar panels in a fixed orientation are receiving light from an indirect angle at virtually all times throughout the year. The light landing on them has less intensity.

As a result, solar panels with 4 kW of capacity in the Solaflect PV Tracker will deliver more energy—measured in kilowatt-hours—than the same solar panels in a fixed array. (See “How does the Solaflect PV Tracker make more energy?” parts 1, 2, and 3.)

And energy is what you want. Capacity is merely a means to the end of producing energy. Your electric bill is calculated on the basis of energy—of kWhs. If you want to reduce your electric bill with a solar array, you want the array that will give you the most energy, the most kWhs, at the best cost.

Nine times out of ten, the most cost-effective solar option for you is going to be the Solaflect PV Tracker.

When you want to compare a proposal from Solaflect with one from another installer, ignore cost-per-watt since that is an apples-to-oranges comparison. Instead, calculate the cost-per-kWh using the expected kWh production from the first year. Of course, any solar array will continue producing energy long past the first year. Limiting this mathematical exercise to the first year is just to make it easier and quicker to get an apples-to-apples comparison.

To do this, look at the proposals and find the cost for the solar array, then divide this number by the expected kWhs to be produced in the first year. Using this value, cost-per-kWh, you can then make fair comparisons between any set of solar proposals.

A real-life example.

We recently provided a proposal to a Vermont farmer for two Trackers. This farmer also received a proposal from another installer for an array that would go on the barn roof. The farmer has a gorgeous place, both as a farm and for solar access with almost no shade at all from trees, buildings or ridge lines.

Here are the numbers to compare the two proposals.

 SolaflectAlternative installer
1. System cost (after tax credit)$26,530$31,375
2. System capacity8,000 watts (8 kW)8,520 watts (8.52 kW)
3. Cost-per-watt (traditional measure): Row 1 divided by Row 2$3.32$3.68
4. Solaflect cost advantage on capacity basis9.8% less than the alternative
5. Expected energy delivered in 1st year12,582 kWhs8,470 kWhs
6. Solaflect energy production advantage48.5% more than the alternative
7. Cost-per-kWh (first year production only): Row 1 divided by Row 5
This is your apples-to-apples comparison.
8. Solaflect cost advantage on energy basis43.1% less than the alternative

The precise values in this example are the result of the particulars at the farm, but they are indicative of the sort of value Solaflect customers receive. If you are thinking of going solar (and you should be!), you should be thinking of going Solaflect.

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    […] you are comparing proposals from Solaflect and other solar installers, be sure to read our FAQ on how to properly compare different proposals so that you make an apples to apples […]

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