Tariff guide

Cosy Octopus is designed specifically for homes with heat pumps. It gives you two windows of cheap electricity each day, timed around when heat pumps work most efficiently. The idea is that you pre-heat your home during the cheap periods and coast through the expensive ones.

How it works

Cosy has three rate bands:

• Off-peak (cheapest): 04:00-07:00, 13:00-16:00 and 22:00-00:00. Nine hours of cheap electricity spread across three windows.
• Standard: 00:00-04:00, 07:00-13:00 and 19:00-22:00. Mid-range rates for most of the day.
• Peak (most expensive): 16:00-19:00. Just three hours during the evening demand spike.

The off-peak rate is significantly lower than the standard Flexible rate. The peak rate is higher. So the tariff rewards you for running your heat pump during those off-peak windows and avoiding heavy electricity use in the evenings.

Why those specific windows?

The early morning window (4-7am) lets you pre-heat your home before the standard rate kicks in. A well-insulated house will hold that warmth for hours. The afternoon window (1-4pm) is timed for when solar generation peaks (reducing wholesale costs) and lets you top up the heat before the evening peak. The late evening window (10pm-midnight) gives you a chance to warm the house before bed at the cheap rate.

It's clever design, but it does depend on your home being reasonably well insulated. If your house loses heat quickly, you'll end up running the heat pump during expensive periods too, which undermines the whole point.

Who is it for?

• Heat pump owners with decent insulation. This is really the target audience. If your home holds heat well, Cosy can save you a lot compared to running a heat pump on a flat rate.
• Anyone with high daytime electricity use. If you work from home and use a lot of electricity between 1-4pm anyway, those hours are cheaper on Cosy.

Who should avoid it?

• Households without heat pumps. The rate structure is designed around heat pump usage patterns. Without one, you're unlikely to benefit from those specific off-peak windows.
• Poorly insulated homes. If your house cools down quickly, you'll need to run the heat pump outside the off-peak windows, and the peak rate is steep.
• Heavy evening electricity users. The 7pm-4am peak rate is the most expensive band. If that's when you use the most electricity, Cosy will cost you more, not less.

Bottom line

If you've invested in a heat pump and your home's insulation is up to scratch, Cosy Octopus is worth a serious look. The six hours of cheap electricity align nicely with how heat pumps are best used. It is a niche tariff, though, and it only makes sense if your heating setup and home can take advantage of those off-peak windows.