Solar panels have been dropping in price significantly over the past decade. According to the National Renewable Energy Laboratory (NREL), the price of solar photovoltaic (PV) modules, which are the most expensive part of a solar panel system, has fallen by over 90% since 2010.
In 2010, the average price of a solar PV module was around $1.50 per watt. By 2020, the average price had fallen to around $0.20 per watt. This decrease in price is due to a combination of factors, including technological advancements, increased production, and economies of scale.
The cost of solar installations as a whole has also decreased, including installation and other balance-of-system costs. According to the Solar Energy Industries Association (SEIA), the cost of a residential solar installation has dropped by 55% since 2010, and the cost of a utility-scale solar installation has dropped by 90% over the same period.
The prices for solar system inverters and charging controllers have also been dropping in recent years. As with solar PV modules, technological advancements and increased production have driven down the cost of these components.
Inverter prices, in particular, have been decreasing due to advancements in inverter design and the availability of lower-cost materials. The cost of solar inverters has fallen by about 50% over the past decade, according to the SEIA.
Charging controllers, which regulate the charging of batteries in solar systems, have also seen a decrease in cost. The price of these controllers has dropped due to increased competition and economies of scale, as more people adopt solar power and demand for solar components increases.
Small controllers can cost as little as $20, or for 20 amps or even 30, up towards $100 especially for higher quality equipment.
There are several inexpensive charging controllers available for solar power systems. Here are a few examples:
- Renogy Wanderer 10A PWM Solar Charge Controller: This is a basic but reliable charge controller that is suitable for small solar systems. It features a backlit LCD screen and can handle up to 120 watts of solar power.
- ALLPOWERS 20A Solar Charge Controller: This is a budget-friendly charge controller that can handle up to 260 watts of solar power. It features an easy-to-read LED display and includes several safety features, such as overcharge and reverse polarity protection.
- EPEVER 30A MPPT Solar Charge Controller: This is a slightly more expensive option, but still relatively affordable compared to other MPPT (Maximum Power Point Tracking) charge controllers on the market. It can handle up to 390 watts of solar power and includes advanced features such as temperature compensation and remote monitoring.
- Sunix 20A Solar Charge Controller: This is a low-cost charge controller that can handle up to 240 watts of solar power. It features an easy-to-use interface and includes several safety features, such as overcharge and over-discharge protection.
On the inexpensive side of things, inverters run on 12 volts, where as more serious solar power enthusiasts will use 48 volt systems. 48 volt systems use arrays divided into batteries grouped in fours, wired in series to yield a 48 volt storage cell.
Inverters capable of running a full 15 or 20 amp circuit from 12 volts run from $100 to $300.
- Krieger 1500 Watt 12V Power Inverter: This is a budget-friendly option that can handle up to 1500 watts (12.5 amps) of continuous power. It includes two AC outlets and a USB port for charging small devices.
- BESTEK 300W Power Inverter: This is a compact and affordable inverter that can handle up to 300 watts (2.5 amps) of continuous power. It features two AC outlets and two USB ports for charging devices.
- Ampeak 2000W Power Inverter: This is a more powerful option that can handle up to 2000 watts (16.7 amps) of continuous power. It includes three AC outlets and a cooling fan to prevent overheating.
- AIMS Power 2000 Watt 12V Pure Sine Inverter: This is a slightly more expensive option, but it provides high-quality power with a pure sine wave output. It can handle up to 2000 watts (16.7 amps) of continuous power and includes two AC outlets and a cooling fan.
15 amp circuits – time per battery
Since we don’t want to overheat the inverter, lets say you want a steady 10 amps at 110 volts and your inverter has 90 percent efficiency.
Battery Life = Battery Capacity / (Inverter Efficiency x Load Power)
Assuming that the car battery has a capacity of 50 amp-hours and the inverter has an efficiency of 90%, here’s how to calculate the battery life:
Load Power = 10 amps x 110 volts = 1,100 watts Battery Life = 50 amp-hours / (0.9 x 1,100 watts) = 50 / 990 = 0.05 hours
So, the car battery would last for about 0.05 hours, or 3 minutes, before it would need to be recharged.
Also keep in mind that lead acid batteries need to stay charged. Draining a car battery to zero volts will damage the battery.
So running a space heater, even on low, would use the battery quickly, but you can use your 10 amp budget in a different fashion.
You could run a 60 watt LED lightbulb, your computer, modem and network switch for less than 1 amp. This would give you a battery life closer to two hours.
You could run a refrigerator or freezer at 600 watts for two hours on a car battery. More amperage is required when the motor starts, but also, the compressor does not run all the time. So you might get two or three times the duration or six hours of running the chest freezer on a car battery.
For a small system like this, ten or 20 batteries would not be uncommon. This would give you time to keep the venison frozen while you are on the computer, for hours, or even a day or two.
If you had enough solar panels to max out a 10 amp charge controller, you can expect to charge a car battery in less than one day. Assuming 4-6 hours of Georgia sunshine, and enough solar panels to produce 10 amps, you could charge a car battery every day. So an array of 20 batteries would take less than 20 days to fully charge. But since the batteries never are fully discharged, the time would be less.
The big expense and effort, then, is not the charge controller, inverter or solar panels, but the batteries. The first thing to consider is how to obtain between eight and 20 car batteries, store them properly and cable them together into an active battery array. Considering eight batteries and the hardware to store them and cable them, this is north of $1,000, but yields hours, or an hour at more load of backup power, charged by the sun, and ready in case of a temporary outage.