Energy simulation in Excel or in Wattix?
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Excel is good enough for energy simulation as long as you calculate one asset and one scenario. Once a battery, solar and chargers must share one grid connection, every quarter-hour depends on the last, and you want to compare scenarios. That is where a spreadsheet breaks down. Wattix simulates every quarter-hour, optimises the battery and compares scenarios side by side.
What is Excel good at?
Almost every installer and consultant calculates in Excel, and for good reason. You set your own assumptions, you can see every formula, and you already have it. For a first estimate with one asset, or a yearly total of consumption and generation, a spreadsheet is fast and good enough.
The business case often stays in Excel too. Payback period, subsidies and financing are calculated with your own assumptions, in your own house style. Wattix does not calculate that business case for you. It delivers the energy flows and costs per scenario, and you take those into your own calculation.
What has changed are the questions. Grid congestion means a battery, a charging hub or a new building has to fit within the same connection, and with dynamic prices every quarter-hour counts. A yearly total does not answer those questions.
How do Excel and Wattix differ?
The table lists the main differences. The rest of the article explains them.
| Excel | Wattix | |
|---|---|---|
| Quarter-hour data | Fits easily: a year is 35,040 rows, a worksheet holds 1,048,5761 | Every quarter-hour of the period in your data |
| Battery control | A rule per quarter-hour, in formulas you build yourself | Optimised over the whole period at once |
| Battery sizing | Trying sizes one by one | Power and capacity calculated automatically |
| Assets per scenario | Every extra asset is an extra column with extra conditions | Battery, solar, chargers, loads and generators together, within the connection |
| Contracts and prices | Model them yourself | Contracted capacity, limits per time block and dynamic prices |
| Comparing scenarios | A copy of the tab or file per variant | Scenarios side by side in one project |
| Report for the client | Charts and screenshots by hand | Report from a template, as a PDF |
| Business case | Completely free, with your own assumptions | Not built in, you export the results as CSV |
| Knowledge of the model | In the file, and often with the colleague who built it | Projects shared within your organisation |
Why does a spreadsheet break down on quarter-hour data?
A year has 35,040 quarter-hours: 365 days of 96 quarter-hours. That number of rows is no problem for Excel, since a worksheet holds over a million1. The problem is how the rows depend on each other.
Take a business with a contracted capacity of 500 kW, solar panels on the roof and a battery for peak shaving. What the battery can do in a quarter-hour depends on how full it is. And how full it is depends on every quarter-hour before. In Excel that becomes a chain of 35,040 formulas in which every row refers to the previous one. A rule like "discharge above 450 kW, charge from surplus solar" has to hold in every row, within the limits of power, capacity and efficiency.
Such a rule decides per quarter-hour, without knowing what comes next. If the battery discharges at ten o'clock for a small peak, it may be empty at eleven for the big one. Whether the battery is too small or the rule is wrong is then hard to tell.
Add chargers, a second roof of panels or a contract with different limits per time block, and every row gets more conditions. Every change affects the whole chain.
How does Wattix calculate a battery?
Wattix works with the same quarter-hour data, but it does not decide quarter-hour by quarter-hour. It optimises the battery's control over the whole period at once. So at ten o'clock the calculation already accounts for the bigger peak at eleven.
If you do not know yet how big the battery should be, Wattix calculates the required power and capacity in one go, instead of you trying sizes one by one. If no battery leaves enough room on the connection to absorb every peak, you see that too.
Because the optimisation sees the whole period, the result is the best achievable control for this data. An EMS in practice does not know the future and will not always match it fully. Allow for that in your advice.
More on battery sizing with Wattix →
We used to combine Excel with a simulation tool for solar systems. It took a lot of time and we couldn't always figure it out, especially when energy storage also had to be factored in. With Wattix we can calculate generation and storage together, run multiple simulations, compare the outcomes, and have a well-founded recommendation in no time.
How do you compare scenarios?
Advice is rarely one calculation. Your client wants to know what a battery delivers, what happens with extra chargers and whether a different contract is enough. In Excel every variant becomes a copy of the tab or the file. Change one assumption and you change it again in every copy.
In Wattix you set up the variants as scenarios in one project, on the same data, and compare the outcomes side by side. A scenario takes a few minutes on average, so you can add another variant at the client's table.
From metering data to report
You upload your client's quarter-hour data as an Excel or CSV file. If there is no metering data, for example for a new building or an expansion, you build a profile in the Data Studio.
At the end you turn the scenarios into a report for your client, from a template, and save it as a PDF. The charts come from the same calculation, so there is no copying and pasting in between. Read more about reporting in Wattix.
Who knows the model?
A good Excel model has often grown over years. It works because the colleague who built it knows exactly what each cell does. That is also the risk: when that colleague is away, the model is hard to hand over and an error is hard to find.
In Wattix, projects belong to your organisation. Colleagues work in the same projects with the same method, and you can read someone else's scenario without first taking the formulas apart.
When should you move from Excel to Wattix?
If you calculate a simple case a few times a year, with one asset and a yearly total, Excel is fine and you do not need Wattix.
Wattix pays off when you regularly:
- calculate several assets together within one connection, such as a battery with solar panels and chargers;
- size a battery for peak shaving or grid congestion;
- show a client scenarios or contracts side by side;
- share the calculation work with colleagues.
Your business case in Excel does not have to go. Wattix delivers the energy flows and costs per scenario, and you export the quarter-hour results as CSV for your own calculation.
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