Time-of-use (TOU) billing changes what a solar system is worth. Under a flat rate, a kWh is a kWh whenever you use it. Under TOU, the same kWh can cost two or three times more at 6 p.m. than at noon — and here’s the uncomfortable part for solar owners: your panels produce the most around midday and taper off exactly as the expensive window begins.
That mismatch is fixable, and mostly for free. The core move is load shifting: rearranging when your house consumes energy so the big loads run while your roof is producing (or during cheap off-peak hours) and the peak window sees as little grid draw as possible. Running a 40-panel array on our own roof, the pattern is unmistakable in the monitoring data — a strong midday production plateau, then the evening cliff. The whole game is scheduling your house around that shape.
First: actually read your rate plan
Everything downstream depends on your utility’s specific windows, so pull up your plan and write down three things: when peak pricing starts and ends, what the peak and off-peak prices are, and whether weekends or seasons differ (they often do — many utilities run different peak windows or prices in summer versus winter).
Labeled example (illustrative, not your rates): a common structure looks like peak from 4–9 p.m. on weekdays at a high rate, with everything else off-peak at a much lower one. If your peak rate is, say, double your off-peak rate, then every kWh you move out of that window is worth twice as much as a kWh saved elsewhere. That’s the leverage.
While you’re at it, find out how your utility credits exported solar. If exports earn much less than the retail rate (increasingly common), self-consuming your own production beats exporting it — which strengthens the case for running loads at midday rather than letting the surplus flow out.
The hierarchy: solar hours first, off-peak second, peak never
For any flexible load, the priority order is:
- Solar production hours (roughly mid-morning to mid-afternoon) — this energy is effectively yours already, especially if export credits are weak.
- Off-peak grid hours (typically overnight) — cheap grid power for anything that can’t fit under the solar curve.
- Peak hours — only what genuinely can’t move: cooking dinner, lights, the TV.
The good news is that the biggest residential loads are also the most movable ones.
The load-shifting schedule
Here’s the working schedule I’d hand any solar homeowner on a 4–9 p.m. peak plan. Adjust the windows to your own rate plan and production curve.
| Load | Flexibility | Best time to run | How to automate it |
|---|---|---|---|
| EV charging | Very high | Midday if the car is home; otherwise overnight off-peak | Departure/schedule settings in the car or charger app |
| Electric water heater | High | Late morning–early afternoon (heat the tank on solar, coast through the evening) | Timer or smart water-heater controller |
| Dishwasher | High | Start midday, or use the delay-start button for overnight | Built-in delay start — nearly every model has it |
| Laundry (washer/dryer) | High | Midday loads on weekends; delay-start on weekdays | Delay start, or just habit |
| Pool pump | Very high | Solar window, split into a midday block | Pump timer — this is often the single biggest easy win |
| A/C or heat pump | Medium | Pre-cool (or pre-heat) the house 1–3 hours before peak, then raise the setpoint during peak | Smart thermostat schedule |
| Cooking | Low | Dinner is dinner — but batch-cook or use smaller appliances during peak | Not worth fighting; minimize instead |
| Battery charging (if you have storage) | Very high | Charge from solar midday, discharge through peak | Set the system to a TOU/self-consumption mode |
Two rows deserve extra attention:
The thermal loads are batteries you already own. A water heater tank holds hot water for hours; a house holds “coolth” for a while after you pre-cool it. Heating water at 1 p.m. on solar and cooling the house down before the peak window starts lets you glide through the expensive hours with the compressor and heating elements mostly idle. It costs nothing but a schedule change.
EV charging dominates if you have one. A single charging session can dwarf every other load in the house. Getting it out of the peak window — onto midday solar when the car’s home, overnight rates when it isn’t — matters more than everything else on the list combined.
Batteries: the brute-force option
Everything above is free. A home battery is the paid upgrade: it charges from your solar surplus at midday and serves the house through the peak window, so even your inflexible evening loads stop touching the grid at peak prices.
Whether it pays back depends entirely on your rate spread and export compensation. A wide peak/off-peak gap plus weak export credits is the strong case; a narrow spread plus full retail export credit is the weak one. Run the math with your own bill before buying — and note that if you’re battery-shopping anyway for backup power, the TOU savings come along free. If you already have storage, make sure it’s set to a time-of-use or self-consumption mode rather than backup-only, or it will sit at 100% doing nothing for your bill.
Verify with your monitoring, then iterate
Every modern solar system ships with monitoring that shows production and (with a consumption meter) household usage. After a week or two of the new schedule, look at the daily graph and ask one question: is there still meaningful grid draw during peak hours? If yes, find out what’s running — the culprit is usually a forgotten always-on load, an A/C schedule that wasn’t updated for the season, or an EV that plugged in at 5 p.m.
If you want to plan rather than just react, NREL’s free PVWatts calculator will estimate your system’s hourly production profile by month for your exact address, tilt, and orientation. That tells you how much midday surplus you realistically have to schedule loads into — and how much the winter production window shrinks, which usually means shifting more loads to the overnight off-peak rate in December than in June.
The realistic payoff
You will not get peak-hour grid draw to zero without a battery — dinner and lights are non-negotiable. But moving the pool pump, water heating, laundry, dishwasher, and EV out of the peak window, plus pre-cooling the house, removes most of the load that was discretionary. Since the kWh you moved were the most expensive ones on your bill, the savings are outsized relative to the effort: a few timer settings, a thermostat schedule, and the delay-start button you’ve been ignoring for years.
Start with the two biggest movable loads in your house, verify the change in your monitoring graphs, and work down the table from there.