Energy Time Planner

What it is for

With a dynamic or time-of-use electricity tariff, the same wash can cost twice as much at 18:00 as at 13:00. This tool takes tomorrow's 24 hourly or 96 quarter-hourly prices and your flexible appliances, each with an earliest start, a finish-by hour, a running time and its energy use, and finds the cheapest plan that respects every deadline and your limit on how many appliances run at once. It compares that plan with simply starting everything as early as possible.

It is a planning model. It does not switch appliances, does not know your appliance's real power curve, and does not assess whether your wiring or fuse can carry several machines at once.

Worked example

The default has a cheap night tariff (0.15 per kWh from 0:00 to 6:00, then 0.35) and two machines that must finish by 8:00: a Washer (2 hours, 1 kWh) and a Dishwasher (3 hours, 1.5 kWh), one at a time. Result: dishwasher 0–3, washer 3–5, Modeled cost 0.375, the same as the Earliest-start baseline, because everything fits into the cheap hours anyway.

A sunnier example with prices that dip at midday, from 0.32 at midnight down to 0.08 at 12:00 and 0.07 at 13:00, then up to 0.42 at 18:00. Three appliances, all with an earliest start of 8:

With Maximum appliances at once 1, the result is "Modeled cost 0.653 (optimal in this model)": washer 10–12 (0.198), dryer 12–14 (0.18), dishwasher 14–17 (0.275). Starting everything at 8 in order would cost 0.799, so the plan saves 0.146. The dryer, the biggest consumer, gets the two cheapest hours. Allow two appliances at once and the cost falls to 0.449: washer 11–13, dishwasher 12–15, dryer 13–15, with a Peak modeled kW of 1.7 instead of 1.2.

How to read the result

• Modeled cost is the plan's energy cost in your price currency. Earliest-start baseline puts each appliance at its first feasible slot in table order; Difference from baseline is the saving.
• Peak modeled kW is the highest combined average power, kWh divided by running hours.
• Optimality proven says Yes when the search checked every relevant option. After 200,000 search steps it stops and says No; the plan is then good but not proven best.
• The chart switches between Appliance schedule and Prices and load. Schedule lists start, end, cost, energy and power per appliance.

Tips and common mistakes

• Hours are slot numbers on one day, 0 to 24. A finish-by hour of 18 means the job must be done by 18:00.
• Enter energy per cycle from the appliance's label or a plug meter. The eco programme often uses less energy but runs longer, so it needs a wider window.
• Use Maximum modeled power if your fuse or a shared circuit cannot carry two heaters at once. It uses average power, not start-up peaks.
• With 96 quarter-hour prices, enter times in quarter hours, such as 7.25 for 7:15 or 1.5 running hours. Times must match the price interval.
• Negative prices are allowed: the plan will happily run appliances when you are paid to consume.

FAQ

Where do I get the prices?

From your supplier's app or the day-ahead price your tariff follows. Paste them comma-separated, 24 or 96 values, including taxes and fees if you want final prices.

Can a job be paused and resumed?

No. Every appliance runs uninterrupted at constant power, like most washers and dishwashers once started.

Why is the saving zero in the default example?

Because the earliest start already falls into the cheap night hours. The optimiser only saves money when the earliest slot is not the cheapest one.

Does it control my devices?

No. Set the start-delay timers on your appliances to the times in the schedule.