Your electric bill keeps climbing, solar ads promise “free power,” and everyone seems to have a different opinion on whether home solar is actually worth it. The truth? Solar can be a financial game-changer—or an expensive disappointment… depending on what you don’t know going in.
Before you sign a contract or dismiss solar altogether, it’s worth understanding how home solar systems really work, what they cost beyond the sales pitch, and how homeowners who do it right lock in decades of lower energy bills.
The first thing you need to know is how much Solar power you need. In the old days, they told you to go around and look at the wattage rating on all your appliances, add them up, try to figure out how long each one runs, etc. But there are major problems with this.
- You are just guessing at how long each one will run.
- The wattage listed is peak or maximum wattage, and usually, appliances use much less.
There is a much easier way: Just look at your electric bill and find the kWh used for a month. You can even look at all your bills and see the trend. If you live in a warm climate, your peak usage might be in the Summer for A/C, or if you live in a Cold climate, it could be in the Winter for Heat.
Next, you need to decide if you want to cover all your usage or just a good chunk of it. Hint: Sizing for peak usage will cost a lot more than sizing for average usage or even just a chunk of your usage.
So if your average monthly usage is 900 kWh, that means: you used 900,000 WattHours in a whole month. Panel output is measured in watts, not Kilowatts. And to know how much it will produce, you need to know how many hours of sunshine it gets. So if you have a 500-watt panel and it gets 5 hours of peak sunshine, that panel produces 2,500 watt-hours of electricity a day.
Next, look at your bill and divide by the number of days. It isn’t always the same; it depends on how often they read your meter. Some bills will tell you the average usage Per Day; otherwise, you need to calculate it: total kWh/month ÷ number of days on that bill = kWh/day.
Find your average “peak sun hours.”
This depends on your location. In the U.S., typical averages:
| Region | Peak Sun Hours / Day |
| Northeast | 3.5 to 4 |
| Midwest | 4 to 4.5 |
| Southeast | 4.5 to 5 |
| Southwest | 5.5 to 6.5 |
| Pacific NW | 3 to 4 |
(“Peak sun hours” means full-power sun equivalent, not daylight hours.)
Example: 5 peak sun hours/day
This is a conservative estimate. I live in Florida, and my panels start producing significant electricity long before I thought they would, often at 8 AM, not at full capacity, but some, even though they face West. And they continue producing until Dusk. So they may produce at peak capacity for 5 hours and at partial capacity for 4 more.
Calculate required system size (kW)
The formula is: System size (kW) = Daily kWh ÷ Sun hours
So if your monthly usage was 900KWh for a 30-day month, that would be 900÷30= 30 kWh per day.
30÷5 peaksun hours = 6 so you need 6KW to cover your average usage.
Just to be safe, account for real-world losses:
Solar systems aren’t 100% efficient. Losses come from:
- Inverter efficiency
- Heat
- Dirt/shading
- Wiring losses
- Panel degradation over time
Industry rule of thumb: add 20–25%
6 kW x 1.25 = 7.5kW
These days, new panels produce 450 to 650 watts each. So 7,500 watts ÷ 500 = 15 panels.
Beware of Solar Salesmen.
They will promise you the moon (or maybe the Sun). Panels are cheap these days (although tariffs on China and rising Silver prices could change that), but you can get good panels for around $200 each if you don’t want the absolute maximum efficiency ones. As of this writing, January 2026. A1 Solar has 450-watt panels for $198 each, 580 Watt panels for $307 each, and 640 Watt panels for $384 each.
If we calculate cost per watt, we get:
- $198÷ 450= .44/watt,
- $307÷ 580=.53/watt, or
- $384÷ 640= .60/watt.
Therefore, if you have enough room on your roof, it is cheaper to get the less powerful panels. But to produce 7,500 watts @ 450 watts /panel, you would need 16.66 panels, so you would have to go with either 16 or 17, and you may not have room. And 17 might make a strange arrangement, and there are other considerations why you might be better off with 16. 16 x 450 = 7200 watts and 16 x $198= $3,168.
If you go with the 640-watt panels you would only need 11.71, so say 12. 640 x 12 = 7,680 watts and 12 x $4,608.
So, either $3,168 for 7,200 watts or $4,608 for 7,680 watts for just the panels, then there is mounting hardware, wiring, meter connections, permits, etc., and labor. Which might come out to $12,000 to $15,000 or a little more. That is without a battery backup.
But that isn’t how a Solar Salesman is going to price it (even though they say they do). What they are going to do is look at your electric bill and find out what you are currently paying, say $200/ month, and they are going to offer to finance the whole system for you for only $180 a month for 15 years. So you think you are going to save $20 a month. (Except that your utility is going to charge you a minimum connection fee of… You guessed it, $20 a month. And you will end up paying the Solar company $32,400 i.e., $180 x 12 months x 15 yrs = $32,400. (and the company will try to get you to sign over any Solar Tax credits to them as well). They may even try to lease the panels to you rather than selling them to you.
Solar salesmen also won’t tell you that without batteries, your system doesn’t provide any electricity when the grid goes down. (Protection against outages is a benefit most people think Solar would give them). But… when the grid is down, grid-tied systems automatically shut down your system to prevent you from electrocuting the linemen. Adding batteries will probably double the cost and add a cutout switch to disconnect your house from the grid if it is down. Unfortunately, you can’t disconnect from the grid without batteries because solar power is too variable to run your house.
If, rather than listening to the Solar Salesmen, you can find a local installer that has been in business for 15 to 20 years, you can probably get them to install the system for $12,000 to $15,000, but you will have to pay the full amount or get a loan. But you will be much better off.
Solar systems have a very long lifespan. Most panels guarantee that they will still provide something like 87% of their rated power 25 or 30 years later. So once you’ve paid them off, you will be getting free power.
Note: The higher wattage panels like the 640-watt ones above are “Bifacial,” meaning that some of the power produced comes from the back side. Some customers claim that reflected light off a white roof can provide that additional power. But they may not produce the full 640 watts. They may produce full power mounted on a rack in the yard, where they will get more sunlight on the back side.
Google’s Project Sunroof can help you calculate what kind of system you need and how it will perform in your location. In locations nearer the equator (like Florida and Texas), panels are almost equally efficient no matter which direction they face (because the sun is almost directly overhead). But in Northern climates, they need to be on south-facing roofs. The online solar estimators will figure all that out and can estimate how much efficiency you lose with a west-facing (or East-facing or North-facing) roof.
Energy Sage can get you competing quotes online. They are still Solar Salesmen, but they are online and basically bidding for your job.
Project Solar can also get you a quote online. So you will be prepared to negotiate when that solar salesman comes knocking.
Good Luck!
