Welcome to ROI Tools

A City Energy salesperson knocked on my door asking if I wanted to convert my electric water heater to gas. I had no idea if the numbers actually worked out. So I built a calculator to find out.

Then I built one for aircon. Then refrigerators. Now there’s a small site of payback calculators specifically tuned to Singapore — SP Group tariffs, NEA Energy Labelling Scheme data, GST, Climate Voucher.

What’s here

• Water Heater ROI — gas vs. electric, with payback period and historical tariff charts.
• Aircon ROI — compare star ratings and system configurations, side-by-side.
• Refrigerator ROI — when does upgrading actually pay back?

Each calculator has its own methodology page exposing every formula. No black boxes.

What’s coming on this blog

Short, honest notes:

• Tariff-watch when SP or City Energy revises their rates.
• Deep dives on the math behind specific decisions (e.g. why an electric storage tank quietly costs you $8/month even when you don’t use it).
• SG-specific rebate explainers — Climate Voucher, CDC schemes, NEA grants.
• Real numbers from actual households who try the calculators.

If a daily energy-bill question is bugging you, drop me a note — it might become the next post.