Why the words matter
Solar quotes and EV spec sheets are full of jargon. Mix up a couple of terms, especially kW and kWh, and you could buy far more solar than you need, or misjudge what a car will cost to run.
This glossary explains the words you'll actually run into, in plain English, and why each one matters when you charge an EV with solar.
Cheat sheet
The seven terms you'll see most often:
| Term | In plain words | Why it matters |
|---|---|---|
| kW (kilowatt) | How fast power flows | Sizes solar systems and chargers |
| kWh (kilowatt-hour) | An amount of energy | Sizes batteries and your daily needs |
| Peak sun hours | Hours of full-strength sun per day | Decides how much your panels make |
| kWh per 100 miles | How much energy a car uses | Decides how many panels you need |
| Net metering (1:1) | Full credit for solar you export | The grid acts as a free battery |
| Net billing / export rate | Lower credit for solar you export | Makes daytime charging more valuable |
| Time-of-use (TOU) | Prices change by time of day | Charge off-peak to save |
The big one: kW vs kWh
This is the mix-up we see most. Think of a garden hose filling a bucket.
Kilowatt (kW) = speed: the hose. It's how fast electricity is flowing right now. A 10 kW solar system can produce power twice as fast as a 5 kW system. A Level 2 home charger delivering 9.6 kW fills your car much faster than a normal wall outlet at about 1.4 kW.
Kilowatt-hour (kWh) = amount: the bucket. It's the total energy produced or used over time. A 10 kW system running at full power for one hour would make 10 kWh; in real life a little less, because of losses. EV batteries are measured in kWh. A Tesla Model Y Long Range holds about 75 kWh.
In short: you use the kW hose to fill the kWh bucket. Solar systems and chargers are sized in kW. Batteries and your daily energy needs are measured in kWh.
Sun and solar panel terms
Peak sun hours: not the same as daylight hours. One peak sun hour means one hour of full-strength sunlight (1,000 watts per square meter), the level panels are rated at. Arizona averages about 6.5 peak sun hours a day, while Washington state gets about 4. So the same panels in Washington make roughly 40% less energy over a year.
System size (kW DC vs kW AC): panels make direct current (DC), but your home uses alternating current (AC). When an installer quotes an "8 kW system," that's usually the DC size of the panels on the roof.
Inverter: the box that turns the panels' DC power into AC for your home. It loses a few percent of the energy along the way.
Microinverters: small inverters fitted under each panel instead of one big box. Enphase is the best-known brand. If one panel is shaded, the others keep working at full strength.
System losses: the energy lost between sunlight and your outlet: inverter, wiring, heat, dust and so on. Together they usually add up to about 14% to 18%. Our calculator allows 18%.
Degradation: panels slowly lose output as they age, about 0.5% a year on average, according to NREL. Over 20 years, that's roughly 10%.
EV and charging terms
kWh per 100 miles: the most useful number for solar planning. It's on the EPA window sticker and at fueleconomy.gov, and it shows how much energy a car uses to drive 100 miles. Lower is better. A Model Y uses about 29; a big electric truck about 48.
Miles per kWh (mi/kWh): the EV version of miles per gallon: how far the car goes on one kWh. A very efficient sedan like the Hyundai IONIQ 6 gets about 4 miles per kWh; a large electric truck about 2. (Note: the number on your car's screen usually doesn't include charging losses, so it looks a bit better than the EPA figure.)
MPGe: miles per gallon equivalent. The EPA counts 33.7 kWh of electricity as one gallon of gas so you can compare EVs with gas cars. For solar planning, the kWh per 100 miles figure on the same label is more useful.
Level 1 charging: a normal 120-volt outlet. About 1 to 1.4 kW, adding roughly 2 to 5 miles of range per hour. Fine for light driving, slow for most.
Level 2 charging: a 240-volt circuit, like the one for an electric dryer. Home Level 2 chargers usually deliver about 7 to 11.5 kW. The U.S. Department of Transportation estimates 10 to 20 miles of range per hour, and powerful chargers add more. That's enough to refill most EVs overnight.
DC fast charging: public chargers that pump in 50 to 350 kW, adding a lot of range in 20 minutes to an hour. Handy on road trips, but usually much more expensive per kWh than charging at home.
Solar-aware (or excess solar) charger: a home charger that speeds up and slows down to match your spare solar, so the car doesn't pull from the grid when a cloud passes.
V2L and V2H: vehicle-to-load means outlets on the car for running a few appliances. Vehicle-to-home means the car can power your house in an outage, with special equipment.
Billing terms
Net metering (1:1): when your panels make more than your home needs, the extra goes to the grid, and your utility credits you the full retail price for it. You can use those credits to charge your EV at night. If you make as much as you use over the year, your charging energy is effectively free; fixed monthly charges still apply.
Net billing (export rate or buyback): many utilities now pay much less for exported solar than they charge for power. In California, for example, exports often earn only around 5 cents per kWh, while US homes pay about 18 cents on average for electricity (EIA, July 2026). That makes charging while the sun shines much more valuable.
Time-of-use (TOU) rates: prices change through the day: cheaper late at night (off-peak), more expensive in the late afternoon and evening (on-peak). Set your EV or charger to charge off-peak, usually while you sleep.
True-up: the once-a-year settlement many utilities do under net metering. Leftover credits may roll over, be paid out at a low rate, or expire, depending on your utility.
Escalator: in a solar lease or power purchase agreement, the yearly price increase, often around 2% to 3%. Always check it before you sign.
An example: why the words matter
Maya, a homeowner in Texas, was told by a salesperson she needed a 12 kW solar system "to cover her new EV's 80 kWh battery."
But Maya knew the terms. Battery size doesn't decide how much energy you use each day; your driving does. She drives 30 miles a day, and her car averages 3 miles per kWh, so she needs only about 10 kWh a day.
Her area gets about 5 peak sun hours a day. A 12 kW system would make roughly 49 kWh a day after typical losses (12 × 5 × 0.82), far more than her car needs. That size makes sense for a whole home, not just an EV. For the car alone, about 2.5 kW of panels would do (2.5 × 5 × 0.82 ≈ 10 kWh a day).
Knowing the terms helped Maya ask the right questions and avoid paying for thousands of dollars of panels she didn't need for the car. And because Texas has no statewide net metering, she also shopped for an electricity plan with a good solar buyback rate.
(Maya is an example, not a real customer.)