CalcStack — free, instant, no signup. The interactive calculator loads automatically.
At 35% peak usage, TOU saves just $47/yr as-is — but shifting 15 points off-peak saves $252. Above 38.5% peak share, TOU loses unless you shift.
Time-of-use billing is a bet on your schedule, and the breakeven is computable before you switch. At 10,500 kWh/yr with a $0.16 flat rate against a $0.24/$0.11 TOU plan, a household at 35% peak-window usage saves only $47/yr as-is — but shifting 15 points of usage off-peak turns it into $252. The line to know: the breakeven peak share is 38.5% — above it, TOU loses money unless you genuinely move load. What moves easily: EV charging overnight (a $390/yr swing alone), pool pumps, delay-start appliances, pre-cooling. What doesn't: 4–7pm air conditioning with everyone home in August. This calculator prices your shape against your utility's actual rate schedule, so the switch is arithmetic, not a flyer's promise.
Households use it before switching plans: at 35% peak usage TOU saves just $47/yr as-is but $252 with real shifting — and above 38.5% peak share it loses unless the EV and the delay-start buttons do their job.
From your meter, not from vibes. Most utilities with smart meters expose hourly usage in their app or web portal — pull a typical month, sum kWh inside the peak window (commonly 3–8pm or 4–9pm weekdays), and divide by total. That share is the input that decides everything, and it's routinely surprising: households that "never run anything during the day" discover the AC alone puts them at 40%+, while work-from-home households with heavy midday loads can sit under 25% if their peak window is evening-priced. Check both summer and winter months if the utility offers seasonal windows — some plans have different peak hours by season. Five minutes in the app replaces every estimate, including this calculator's default.
The schedulable loads, in order of prize size. EV charging is the giant: 3,000 kWh/yr moved from peak to off-peak is a $390/yr swing on the default rates — set the car or charger to midnight and it's done forever. Pool pumps: pair the variable-speed schedule with off-peak hours and the two calculators stack. Dishwasher and laundry delay-start buttons exist exactly for this — the 4-hour delay moves dinner dishes to off-peak with zero lifestyle cost. Pre-cooling: run the AC to 72° by 3pm, let it coast to 76° through the peak — thermal mass is a battery, and in dry climates this alone shifts the biggest summer load. What DOESN't shift: cooling a full house during a heat dome with everyone home — the honest limit of TOU is the household whose peak usage is survival, not schedule.
It depends entirely on how YOUR plan values exports, and it can flip the answer. Under net metering at retail rates, TOU and solar coexist fine — your midday generation offsets peak-priced usage. Under net-billing or export-compensation plans (increasingly common — California's NEM 3.0 is the template), midday exports earn a fraction of retail while evening imports cost peak rates: the duck curve priced into your bill. There, the winning move is storage or load-shifting INTO midday (run the pool pump and dishwasher at noon off your own panels, not at midnight off the grid) — the opposite schedule from the no-solar TOU playbook. The rule: run both this calculator and the solar payback calculator on the SAME rate plan you'll actually be on, because utilities reprice TOU windows annually and a plan that won in 2025 can lose in 2027.