Why WattSimple
Numbers you can actually trust
Real specs, local electricity rates, and code-correct math, so the estimate matches your bill, not a generic default.
Per-model depth
Real specs for every EV, not one-size-fits-all defaults.
Per-state rates
Local electricity prices so estimates match your bill.
Electrical accuracy
Breaker and NEC math done right, where others are vague.
Instant & free
No sign-up, no email. Results update as you type.
01Calculators
Calculators that do the real math
39 free tools for EV charging, EV costs, home energy and solar: instant results, NEC-correct electrical sizing, and your own electricity rate.
Browse all calculators- Vehicle
- 2024 Tesla Model Y
- Battery
- 75 kWh
- Charge
- 20% → 80%
- Rate
- 16.5¢/kWh (US avg)
per session$8.24
50.0 kWh from the grid · 45 kWh into the battery · 10% charging loss
Try it with your carSpace Heater
1,500 W÷120 V=12.5 A
Amps = watts ÷ volts (single-phase, resistive load)
02Converters
Every electrical conversion, one tap away
34 converters for watts, amps, volts, kilowatt-hours, BTU and more; each one shows the formula behind the answer.
Open the converters03Guides
Plain-English guides, checked against the code
495 guides across 8 topics (EV charging, panels and wiring, backup power, solar and more) written to answer the question, not to pad the page.
Read the guidesElectrical Panels & Circuits 5 min read
Ringless Meter Socket: How It Differs From a Ring-Type Socket
On a ringless socket the cover fits over the meter's base and the utility seals the cover. On a ring-type socket a separate sealing ring clamps the meter to a rim on the cover, and the seal goes on the ring. Same metering, different hardware, and the utility decides which it accepts.
Read the guideElectrical Panels & Circuits 6 min read
Service Disconnect Breaker: What It Is and Where Yours Is
The service disconnect breaker is the one switch that kills power to everything downstream of it. Recent NEC editions require an emergency disconnect on the outside of a dwelling, so first responders can cut power without entering the building.
Read the guideElectrical Panels & Circuits 8 min read
320 Amp Meter Base: Class 320 Socket for 400 Amp Service
Class 320 is the meter socket's continuous rating, and 320 is exactly 80% of 400, so a 320 amp meter base is what most 400 A residential services use. It commonly feeds two 200 A panels or a meter-main with two 200 A breakers.
Read the guide04Gear
Gear picks built from spec sheets
18 buying guides comparing 93 products on manufacturer specs: chargers, outlets, testers, backup power and more. No invented prices, no fake ratings.
See the buying guidesEV charging
Backup power
| Breaker | Min. copper (NM-B) | Typical use |
|---|---|---|
| 15 A | 14 AWG | Lighting, general outlets |
| 20 A | 12 AWG | Kitchen, bath, garage outlets |
| 30 A | 10 AWG | Electric dryer, water heater |
| 40 A | 8 AWG | Electric range, 32A EV charger |
| 50 A | 6 AWG | Range, 40A EV charger, NEMA 14-50 |
| 60 A | 4 AWG | 48A EV charger, subpanel feed |
NEC 310.16 and 334.80 · confirm with your local code
05Reference
Reference charts you'll actually bookmark
13 look-up charts (wire and breaker sizes, appliance wattage and amperage, EV specs and connectors) each with its source.
All reference charts06State rates
Your state's rate changes the answer
Residential electricity rates for all 50 states and DC, plus average bills, EV charging costs and heat pump costs state by state.
Find your stateUS average 16.5¢/kWhEIA residential averages, ¢/kWh
- EV Charger Installers
- 611
- Solar Installers
- 255
- Generator Installers
- 505
- Heat Pump Installers
- 506
- Electricians
- 599
- Insulation Contractors
- 389
- States covered
- 51
07Installers
When it's time to call a pro
One search for every home energy project: EV chargers, solar, standby generators and home batteries. Pick the job, enter your ZIP, and get the pros in your state sorted nearest to you.
Solar Installers by state: CaliforniaTexasFloridaNew YorkPennsylvaniaIllinoisOhioGeorgiaNorth CarolinaMichigan
Questions