Quick answer
An electric car driven 12,000 miles a year uses roughly 3,600 kWh, which takes about 3 kW more solar, around 8 extra panels, in northern Illinois. A heat pump replacing gas heat can add several thousand kWh more, mostly in winter. Size your system for the load you'll have, and charge during the day or on a time-based ComEd or Ameren rate.
How much electricity does an EV use in Illinois?
Most electric cars use about 0.25 to 0.35 kWh per mile, a bit more in Illinois winters, when batteries and cabin heat work harder. At about 0.3 kWh per mile:
| Miles per year | Electricity used | Extra solar | Extra panels |
|---|---|---|---|
| 8,000 | 2,400 kWh | ~2 kW | ~5 |
| 12,000 | 3,600 kWh | ~3 kW | ~8 |
| 15,000 | 4,500 kWh | ~3.8 kW | ~10 |
Central and southern Illinois need slightly less, since panels there produce more per kW.
How much does a heat pump add to my electric bill?
It depends on your home's size, insulation and what the heat pump replaces. Switching from gas to an all-electric heat pump often adds several thousand kWh a year, most of it from December to February, when panels produce the least. Replacing an old central air conditioner with a heat pump can lower summer use at the same time.
Because winter heating load lines up poorly with winter sun, net metering credits from spring and summer do much of the work. Ask your installer to size from a heating estimate for your home, not a national average. ComEd and Ameren also offer heat pump rebates through participating contractors; amounts change, so check your utility's current offers.
Should I charge my EV during the day or at night?
Charging while the sun is shining uses your solar directly, which saves the full electricity rate rather than earning the lower export credit. If the car is home during the day, a charger that follows your solar output works well.
If you charge overnight, a time-based rate can make that power cheaper:
- ComEd: a Delivery Time-of-Day rate launched in February 2026 charges less for delivery overnight (9 p.m. to 6 a.m.) and more in the afternoon peak, with a $2 monthly bill credit per enrolled EV for up to 24 months. ComEd has said a combined supply-and-delivery time-of-day rate is coming.
- Ameren Illinois: Power Smart Pricing charges hourly market prices, usually lowest overnight and on weekends, and a separate EV rate gives a delivery credit for charging from 11 p.m. to 7 a.m.
A battery can store midday solar for evening charging; see the Illinois battery rebate guide.
How should I size solar if I'm getting an EV or heat pump later?
- 1
Start from your last 12 months of use
Your bills show your baseline.
- 2
Add the new load
Use about 0.3 kWh per mile for an EV, and a heating estimate for a heat pump.
- 3
Size for the total, within reason
Under the post-2025 rules, oversizing far beyond what you'll use earns only supply-rate credits.
- 4
Leave room to expand
If the new load is a few years off, ask about panel space and an inverter that can grow later.
Enter a higher bill in the solar savings calculator to see how a bigger system changes cost and payback.
Sources
This guide is general information, not tax, legal or financial advice. Incentive programs change, so confirm current terms with your installer, your utility and a tax professional.