Demand charge interval analyzer

How much of our electric bill is one bad 15 minutes, and what would it take to remove it?

Paste the interval data your utility lets you download (15- or 30-minute readings, usually a Green Button CSV) and enter the demand charge from your bill. The tool finds each month's peak and when it happened, the charge it set, any ratchet carrying a past peak forward, and a table of what holding demand to a lower cap would save, the battery energy that would take, and a rough payback.

Arithmetic on the data you paste. Not engineering, energy, tax, legal or financial advice. Real tariffs have rules this does not model, such as time-of-use demand tiers, power-factor charges and seasonal rates. The example data is a synthetic placeholder, not a real site or benchmark.

Your interval data

Paste CSV (a timestamp column and a usage column)

Or choose a CSV file (read in your browser, never uploaded)

Readings are

Your tariff and options

Demand charge ($ per kW per month)

Demand ratchet (% of highest prior peak, blank if none)

Minutes per reading (blank to detect)

Battery cost ($ per kWh, optional)

Inverter and install cost ($ per kW, optional)

Usable share of battery capacity (%)

Rate and ratchet are on your bill or tariff sheet. Battery costs are only used for the payback column.

Questions people ask

What is a demand charge?

Many commercial electricity tariffs bill not just for energy used (kWh) but for the highest average power drawn in any 15- or 30-minute window of the billing month (kW). That one interval is multiplied by a rate, often $10 to $25 per kW, so a single short spike can set a large part of the bill.

What is a demand ratchet?

Some tariffs bill at least a set percentage, often 50% to 90%, of the highest demand reached in the previous 11 months, even if this month was quiet. A ratchet makes one bad afternoon cost money for a year, which is why the tool shows billed demand next to measured demand.

Where do I get interval data?

Most utilities let commercial customers download 15-minute data from their online account, often as a Green Button CSV. Paste the file contents here, or use the file picker. The tool reads the date and time column and the usage column on its own and tells you which it chose.

Is a battery worth it for peak shaving?

It depends on how tall and how long your peaks are. The cap table shows, for each level you could hold demand to, the yearly saving, the battery energy needed to ride through your longest peak above that level, and a rough payback from the costs you enter. Short, tall peaks pay back far faster than long, shallow ones. Load shifting or staggering equipment starts can capture some of the same saving for far less.

Not decided

Whether your tariff has time-of-use or seasonal demand tiers, power-factor or reactive charges, how your utility measures the interval, whether a battery or controls suit your site, incentive programs, equipment warranties and safety, and the actual installed cost. Ask your utility, an energy consultant or a licensed electrician.