Anonymous

# Kilowatt/Hour question?

I am trying to figure this out can u help?

i need help. i got this step:

Number of solar panels: 2

Equipment Cost: \$3,800.00

NC Tax Credit: \$1,330.00

US Tax Credit: \$1,140.00

Total Credits: 65%

Equipment Cost after Credits: \$1,330.00

Generated Watts: 380

Generated Kilowatt/Hour: 1.256

it all went fine, but to the next step i do not get the logic behind it:

• The savings is the number of kilowatt-hours generated per year times the billable kilowatt-hour, which is \$0.1048. The billable kilowatt-hour is what you pay if you use power from the grid as opposed to generating it yourself.

so i take the last computed value (that is kilowats per day, multiply with 365 days in an year and then multiply with the price per kilowatt, right)?

Relevance
• Anonymous

I tried to reconcile your numbers. If you generate 380 watts = .38 kilowatts, and that is good for only 3.3 hours/day, then you get what you wrote:

1.256 kilowatt-hour (NOT kilowatt/hr) which I'm assuming is the power generated on an average day.

You can treat dimensions just the way you do any other algebraic expression, so

1.256 kwh/day * 365 days/yr * .1048 dollars/kwh = dollars/yr

Note that kwh in numerator & denominator cancel each other out. Similarly with days. So you are left with dollars per year -- just what you wanted.

• Anonymous

I would suggest this: Think of a watt as 1 watt-hour divided by 1 hour.

therefore, 380 watts = 0.38 kilowatts = 0.380 (kilowatt-hour)/hour.

that is, the watts generated equals 0.38 kilowatt-hour per hour.

Now, there are 24 x 365 hours in a year. That is, 8760 hours/year.

Therefore, power generated in a year is 0.38 kW-hour/hour x 8760 hours/year.

That is, 3328.8 kilowatt-hour / year.

At the rate of 0.1048 \$/kilowatt-hour, the savings come to 348.9 \$/year.

Hope that is what you were looking for. I would suggest that you clear up any confusion between watts and watt-hours. Watt is the unit of power, that is, the amount of energy spent/generated per unit time. Watt-hour and kilowatt-hour are just units of energy. Another way to think of this is that, if energy can be compared to the distance a person walks, then power is the speed at which he walks.