How Home Solar Panels Work
From photons hitting silicon to kilowatt hours flowing into your home — here's how solar panels, inverters, and net metering all fit together, plus how to estimate what a system would do for your bill.
Muhammad founded KilowattKit after spending hours trying to decode confusing electricity bills — and realising there were no simple, jargon-free tools to help ordinary homeowners understand their energy costs. He researches electricity rates, EV charging, solar payback, and heat pump economics across the US, UK, Canada, and Australia.
☀️ Key Takeaways
- ✓Solar panels convert sunlight into DC electricity; inverters convert that to usable AC
- ✓Net metering credits you for surplus energy you export to the grid
- ✓A typical 6 kW system produces 7,000–9,000 kWh/year in the US — covering most homes
- ✓Payback is typically 6–10 years; panels last 25–35 years
- ✓The US federal ITC gives a 30% tax credit on system cost (through 2032)
Step 1: Sunlight → DC Electricity
Each solar panel contains dozens of photovoltaic (PV) cells made from silicon. When photons from sunlight strike the silicon, they knock electrons loose, creating a flow of electricity — the photovoltaic effect, discovered in 1839.
This current is direct current (DC) — electrons flowing in one direction. A single cell produces about 0.5–0.6 volts. Cells are wired in series within each panel to reach 30–40 V, and panels are wired in series strings to reach the inverter's input voltage (typically 200–600 V for residential systems).
| Panel type | Efficiency | Typical output | Best for |
|---|---|---|---|
| Monocrystalline | 20–23% | 380–440 W | Limited roof space, maximum output |
| Polycrystalline | 15–18% | 290–350 W | Budget installs, large roof space |
| Thin-film (CIGS) | 10–13% | 180–250 W | Flexible surfaces, low-light performance |
Most residential installs today use monocrystalline panels (370–440 W each). Panel output is rated at Standard Test Conditions (1,000 W/m², 25°C) — real-world output is 10–25% lower.
Step 2: DC → AC via the Inverter
Your home appliances run on alternating current (AC) — 120/240V in North America, 230V in the UK and Australia. The inverter converts the DC electricity from your panels into AC that matches your grid's voltage and frequency (60 Hz in US/CA, 50 Hz in UK/AU).
Modern inverters are 95–98% efficient at this conversion. They also monitor panel output, synchronise with the grid, and automatically disconnect during a grid outage (for safety — to protect utility workers).
Step 3: Net Metering — Your "Solar Bank Account"
When your solar panels produce more electricity than you're using — a sunny afternoon when you're at work — that surplus flows back to the grid through your meter. Net metering means your utility credits you for this exported power.
Think of it like a bank account: you deposit surplus daytime energy, and withdraw it at night or on cloudy days. The exact credit rate varies by utility and country:
| Country | Net metering policy | Export rate (typical) |
|---|---|---|
| 🇺🇸 United States | Full retail net metering in ~30 states; some states have reduced NEM 3.0 (e.g. California) | $0.08–$0.16/kWh |
| 🇬🇧 United Kingdom | Smart Export Guarantee (SEG) — utilities pay for exported electricity | £0.04–£0.15/kWh |
| 🇨🇦 Canada | Varies by province — Ontario, BC, Nova Scotia have net metering programs | $0.05–$0.13/kWh |
| 🇦🇺 Australia | Feed-in tariff (FiT) varies by state and retailer | $0.02–$0.10/kWh |
Sizing a Solar System for Your Home
The key formula is simple:
| Location | Peak sun hours/day | Annual kWh per kW installed |
|---|---|---|
| Phoenix, AZ (US) | 6.5 | ~1,850 |
| Los Angeles, CA (US) | 5.5 | ~1,600 |
| New York, NY (US) | 4.5 | ~1,250 |
| London, UK | 2.8 | ~950 |
| Toronto, CA | 3.8 | ~1,150 |
| Sydney, AU | 5.2 | ~1,500 |
Calculate your solar payback period
Enter your annual usage, system cost, and electricity rate to see payback period, 25-year savings, and ROI — including ITC tax credit.
Costs and Incentives
Solar prices have fallen 90% since 2010. A typical 6 kW residential system now costs $15,000–$21,000 before incentives in the US — and significantly less after the federal tax credit.
Credit on total system cost (equipment + installation + battery). Available through 2032. No cap for residential. A $18,000 system → $5,400 back on your taxes.
Solar panels, batteries, and heat pumps have 0% VAT (reduced from 5% in 2022, extended through 2027). Check the Smart Export Guarantee for export payments.
Canada Greener Homes Grant offered up to $5,000 for solar (program currently paused; check CRA for latest). Provincial programs vary widely.
Small-scale Technology Certificates (STCs) reduce upfront system cost by ~$2,000–$4,000 depending on location and system size.
Adding a Battery: Is It Worth It?
A home battery stores surplus solar power for use at night or during outages. The most common options are the Tesla Powerwall (13.5 kWh, ~$10,000–$12,000 installed) and similar units from Sonnen, Enphase, and LG.
Battery makes sense when...
- ✓Your utility has low or no net metering export rates (exporting is "wasted")
- ✓You have time-of-use rates with large peak/off-peak price differences
- ✓You have frequent power outages and need backup power
- ✓You want to maximise solar self-sufficiency
Battery is harder to justify when...
- ✗You have full retail net metering (grid is your "free battery")
- ✗You're on a flat electricity rate with no TOU pricing
- ✗Your primary goal is just to reduce bills (payback often 15+ years for battery alone)
Frequently Asked Questions
How many solar panels do I need to power a house?
A typical US home using 900 kWh/month needs about 20–25 panels (400W each) in a sunny location, or 25–30 panels in cloudier climates. Your roof's orientation, shading, and local sunshine hours are the key variables — use a solar sizing calculator for a personalised estimate.
Do solar panels work on cloudy days?
Yes — panels produce power from diffuse light, not just direct sunlight. Expect 10–25% of peak output on heavily overcast days, and 50–80% on partly cloudy days. Germany, one of the world's leading solar markets, gets similar sunshine to Canada and still benefits enormously from solar.
What happens to solar energy at night?
Without storage, solar produces nothing at night and you draw from the grid as normal. With a battery (e.g. Tesla Powerwall), you store daytime surplus for evening use. Net metering lets you "bank" surplus with the utility during the day and draw it back at night as a credit.
How long do solar panels last?
Most panels carry a 25-year performance warranty guaranteeing at least 80% of rated output. In practice, modern panels degrade at about 0.5% per year, meaning they'll produce about 88% of original output after 25 years. Physical lifespan is often 30–40 years.
What's the difference between a string inverter and microinverters?
A string inverter converts DC from all panels through one central unit — cost-effective but the whole system is dragged down by shade on one panel. Microinverters (or DC optimisers) are attached to each panel independently, so shading one panel doesn't affect the rest. Microinverters cost more but generate 5–25% more energy in shaded roofs.