Outcome
By the end of this lesson, you will be able to read the Estimated Savings percentage on a schedule, compute it from the painted grid, and turn it into a dollar figure yourself.
| Prerequisites | T0 M0.3 (the math), L1-L5 |
| Time | 9 minutes |
1. Concept
Once you paint a schedule, ZopNight shows what it is worth as a single number: Estimated Savings, a whole-number percentage.
The number answers one question: of the week’s 168 hours, what share does this schedule keep the resources stopped?
What the form shows
Under the weekly grid in the schedule form, three cards update as you paint:
ESTIMATED SAVINGS ACTIVE HOURS INACTIVE HOURS73% 45h 123hThe schedule detail page shows the same three figures in its stats row. Hover the info icon next to Estimated Savings and the tooltip spells out the sentence behind the number:
Resources are stopped 123 of 168 hours per week,saving an estimated 73% on compute costs.The same percentage appears as “Saving 73%” on the schedule’s card and in the savings column of the Schedules list.
There is no dollar figure, no monthly total and no annual projection on the schedule. The percentage is the whole estimate.
The math, step by step
1. Active hours per week Count the painted (running) cells in the grid.
2. Inactive hours per week 168 - active hours
3. Estimated Savings inactive hours / 168 x 100, rounded to a whole numberThe grid works in 60-, 30- or 15-minute cells, depending on the minutes your crons use, so active hours can be a fraction such as 45.5. The percentage is always rounded to a whole number.
The four templates, worked
TEMPLATE ACTIVE INACTIVE SAVINGS──────────────────────────────────────────────────────────────────────────Business Hours (Weekdays 9AM-6PM) 45h 123h 73%Dev Hours (Weekdays 8AM-10PM) 70h 98h 58%Nights Only (8PM-8AM Daily) 84h 84h 50%Weekends Off (Stop Fri 7PM, Start Mon 7AM) 108h 60h 36%Business Hours: 9 running hours x 5 weekdays = 45. 123 / 168 = 73.2%, shown as 73%.
What the percentage depends on, and what it does not
The percentage comes only from the painted grid. It does not depend on:
- How many resources are attached. An empty schedule and one with 500 resources show the same number for the same grid.
- Which resources they are. A large database and a small dev VM count the same.
- Price. No rate, rack or billed, goes into it.
That is why the tooltip says “on compute costs”: the percentage is the share of running hours removed. Storage attached to a stopped resource usually keeps billing, so the share of the whole bill you save is lower than the percentage.
Turning the percentage into dollars
Do it yourself, with the attached resources’ always-on monthly compute cost:
always-on monthly compute cost x Estimated Savings= $12,000 x 73% = $8,760 a month (projected)For the cost base, use the cost ZopNight shows for each attached resource, or the spend in Costs → Reports. The same multiplication appears in one place in the product: when you save a change to a schedule, the Update Schedule dialog offers View Blast Radius, which lists each affected resource’s monthly cost with its current and after-change savings in dollars, computed by applying the old and new percentages.
Projected vs. realized
The percentage is a projection made from the grid. What actually happened shows up later, from billing and state history, in Costs → Reports, which shows the savings figure and its trend over time (T0 M0.4 covers how billing-connected and rack-rate organizations differ).
Realized savings usually come in below the projection. Common causes:
- Overrides keep resources running through stopped hours (M1.5).
- Manual starts between crons persist until the next stop cron.
- Failed actions, for example a missing permission, leave a resource running.
- Storage and other always-billed costs are not affected by stopping.
If the gap is large, look at the resource’s state history (M1.6) before you change the grid.
When the percentage looks wrong
100%. The grid has no running cells, so the resources never start. A schedule saved with no crons also shows 100%. Usually an empty or unfinished schedule.
0%. Every cell is painted: the resources run all week and the schedule never stops them.
Suspiciously high, such as 97%. A one-hour running window on weekdays leaves 163 inactive hours. The arithmetic is right; the schedule design is probably wrong. Check the grid against how the team actually works (L3).
2. Demo
A team sizing a new schedule before taking it to Finance:
SCHEDULE: dev-staging-business-hoursTIMEZONE: Europe/BerlinRESOURCES: 187 attached (EC2, RDS, EKS node groups)
GRID Template "Business Hours (Weekdays 9AM-6PM)", then Friday repainted to stop at 4 PM (the team leaves early). Active hours: 43h (4 x 9 + 7) Inactive hours: 125h Estimated Savings: 125 / 168 = 74.4% → shown as 74%
DOLLARS (done by the team) Always-on monthly compute cost of the 187 resources, from Costs → Reports: $48,700 Projected savings: $48,700 x 74% = $36,038 / month
DECISION Save the schedule. Quote the projection as "up to about $36,000 a month on compute", and re-check Costs → Reports after 30 days for the realized figure.The team’s projection is defensible because every step is visible: the grid gives the hours, the hours give the percentage, and the cost base comes from ZopNight’s own cost data. They quote it as a ceiling, not a promise, because overrides and manual starts will eat into it.
3. Hands-on (5 min)
For your test schedule:
1. Open the schedule (Schedules → click the schedule).2. Read the stats row: Estimated Savings, Active Hours, Inactive Hours.3. Hover the info icon next to Estimated Savings and read the tooltip.
4. Verify the math: - Active hours/week from the grid: ____ - Inactive: 168 - active = ____ - Inactive / 168 x 100, rounded = ____% - Does it match the stats row?
5. Click Edit, paint one extra running hour on one day, and watch the three cards in the form change. Then cancel without saving.
6. Optional: estimate the dollars. Multiply the attached resources' always-on monthly compute cost by the percentage.4. Knowledge check
Q1
A schedule shows Estimated Savings of 73%. That number is calculated from:
A. The attached resources’ rack rate over the last 30 days
B. Billed cost of the attached resources after discounts
C. A fixed savings figure set for each resource type
D. The share of the week’s 168 hours the grid leaves stopped
Show answer
Correct: D. Estimated Savings is inactive hours divided by 168, rounded to a whole number. No price of any kind goes into it, which is why it works the moment you paint the grid.
Q2
A schedule shows 73% Estimated Savings. After 30 days, Costs → Reports shows realized savings well below 73% of the resources’ compute cost. Most likely diagnosis:
A. The percentage was calculated with the wrong rack rate
B. ZopNight rounds the percentage up for display
C. Overrides, manual starts or failed stops kept resources running
D. The cloud provider bills stopped resources at the running rate
Show answer
Correct: C. The percentage assumes every stopped hour in the grid is really stopped. Overrides, manual starts that persist until the next stop cron, and actions that fail (for example on a missing permission) all keep resources running. Check state history before you change the grid.
Q3
A team attaches 50 more resources to a schedule with a 58% Estimated Savings. What happens to the percentage?
A. It stays at 58%, because it depends only on the grid
B. It rises, because more resources means more savings
C. It falls, because new resources dilute the average
D. It is recalculated from the new resources’ costs
Show answer
Correct: A. The percentage is a share of hours, not of dollars. Adding resources raises the dollar value of the schedule, which you compute by multiplying the larger cost base by the same 58%.
5. Apply
Where the percentage appears:
- Schedule create and edit form: Estimated Savings, Active Hours and Inactive Hours cards under the grid
- Schedule detail page: the same three figures in the stats row, with the tooltip
- Schedules list: “Saving N%” on each card, and a Saving column in the list view
- Update Schedule → View Blast Radius: current and after-change savings in dollars for each affected resource
- Realized savings: Costs → Reports
For what actually happened to a resource after the schedule ran, see M1.6 L1: State history timeline.
Module quiz
You have now completed all six lessons of M1.3. Take the module quiz: 10 questions, 80% to pass.