Solarazma (Free Edition) V1.10b

This utility allows you to model various solar installations against various energy tariffs, to understand what your savings (or even profit) might be. Check this accompanying video:

Although best efforts have been taken to ensure a reasonable level of accuracy, this utility may contain errors - therefore no warranty is provided. It must be used at your own risk.

Solar and Inverter

Solar Array Size: kWp

The size of your solar array. Got more than one array?

Inverter Size: kW

Refer to the datasheet of your inverter for this value.

Export Limitation: kW

If your Distribution Network Operator (DNO) has placed a limitation on your export, enter that limit here.

Solar Array Performance


If your array is South-facing and it is the height of summer, then set this value to 100%. Otherwise, reduce according to the direction of your array, the season, and the weather.
For example, on a cloudy day, you might only get 30-50% of what you'd get with bright sun. And in winter, the sun will be much lower in the sky, so reduce by 50-70%.


The number of hours of sun is dependant on the season as well.

Want to use a much more accurate solar model?


Battery Size: kWh

Battery Type:

Battery AC-DC Conversion Losses: %

An AC-coupled battery has higher AC/DC conversion losses as there are three conversions (DC-AC from the solar array to the home, AC-DC into the battery, and DC-AC from the battery to the home). A DC-coupled battery will have a single conversion (DC-AC from the battery to the home).

Maximum Battery Charge/Discharge Rate: kW

Refer to the datasheet of your battery for this value.

Initial Battery Level: %


Normally this will be set to zero, but if you're finding that you have charge left at the end of the day, you can set this to that level, or indeed any other level, to see the effect on the next day.

Forced Charging Schedule

Number of Hours:
Starting Time:

Set this if you are force charging your battery (for example, during an off-peak period).

Want more forced charging options or an additional period?

Forced Discharging Schedule

Number of Hours:
Starting Time:

Set this if you are force discharging your battery (for example, during a peak period).

Want more forced discharging options or an additional period?

Home Energy Consumption

Usage Profile:

Select the usage profile that most closely fits your daily usage.

Total Daily Consumption: kWh

For example, divide your annual or monthly electricity bill by the number of days in the year/month.

Base Load Per Hour: kWh

The "always on" level of power draw for your home.

Custom Usage Profile

Click "Use as Custom Profile" to populate this field with the current usage profile; a comma-delimited list of 24 values, each representing the kWh used per hour across the day. Modify these values as you wish then click "Use as Custom Profile" again to activate those changes.


You can go back to the templated usage profiles above at any time by clicking "Disable Custom Profile".

Additional Energy Consumption

Number of Hours:
Starting Time:
Power Rate: kW

Use this to add in any additional consumption you might have, for example an EV or heavy appliance use on certain days.

Energy Tariff

The default settings here are for Octopus Energy's Flux tariff (Southern England) at 1 July 2023 prices. Please adapt for your own tariff prices.

Import Rates

Default Import Rate: £

Off-peak Import Rate: £
Number of Hours:
Starting Time:

Peak Import Rate: £
Number of Hours:
Starting Time:

Need an additional peak or off-peak import rate?

Export Rates

Default Export Rate: £

Off-peak Export Rate: £
Number of Hours:
Starting Time:

Peak Export Rate: £
Number of Hours:
Starting Time:

Need an additional peak or off-peak export rate?

Note: standing charges are not included in the calculations as they are fixed costs, regardless of usage.

Recent Changes

Fixed a problem with export limits when forced discharging.

You can now save and load the settings :-)

Each setting is now validated.

Ability to enter a custom energy consumption profile.

The tariff and other charts have had slight improvements.

An export limitation field has been added.

The profit/loss calculation now takes into account any initial charge in the battery.

Known Issues

None identified.

If you experience any issues, please let me know.

© Gary Does Solar. All rights reserved.

Summary at the End of the Day

Import Cost


Export Revenue


Battery Level




Solar Generation

Home Energy Consumption

Energy Tariff

Energy Import and Export

Battery Level (State of Charge)

Detailed Calculations

An explanation of the profit will appear here.