Charging Solar Batteries at Night: Why Off-Peak Top-Ups Cut Your Bills

A solar battery is not only for storing sunshine. On the right tariff, you can charge it from the grid overnight at a cheap rate and use that stored energy the next day — when electricity costs much more.

That is one of the biggest reasons battery storage pays back faster for homes and businesses around Spalding and Lincolnshire. Solar fills the battery when the sun is out. Off-peak night charging fills any gap so you start the morning with cheap energy already stored.

How night charging works

Most modern home and commercial batteries can be set to:

1. Charge from solar first during the day
2. Top up from the grid in a cheap overnight window if the battery is not full
3. Discharge during the day (and early evening) so you buy less peak-rate electricity

You do not sit there switching it on at midnight. A compatible inverter and tariff — often called an EV or intelligent off-peak tariff — tells the system when the cheap window is. Typical overnight rates in 2026 are often around 7–12p per kWh. Daytime and peak rates are commonly 24–30p.

The gap between those two prices is the saving.

A simple example

Say you have a 10 kWh usable battery and you top it up overnight at 9p/kWh.

• Cost to fill: about 90p
• Same 10 kWh bought in the day at 26p/kWh: about £2.60
• Saving on that cycle: about £1.70

Do that most nights of the year and it adds up — especially in winter, when solar generation is lower and the battery would otherwise sit half empty.

On a larger commercial battery the same idea scales. A 50 kWh overnight charge at 9p costs around £4.50. Using it instead of 26p daytime power avoids roughly £13 of grid imports.

Why this matters more in winter

Lincolnshire winters are long and grey. Panels still produce, but not enough to fill a battery every day — particularly if you have heating, refrigeration, or a busy household.

Night charging means:

• You are not waiting for a sunny day to have stored power
• Morning and daytime loads run on cheap overnight electricity
• Solar still charges the battery whenever it can, so you are not paying for energy the roof already gave you
• You are less exposed to daytime price spikes

Solar and night charging work together. The battery prefers free solar. The grid only fills what the sun did not.

Who benefits most

Night charging is worth setting up if:

• You already have — or you are fitting — battery storage with solar
• Your supplier offers a genuine overnight or EV-style cheap window
• You use a lot of electricity in the morning and through the day (home heating, EV charging, cold stores, workshops, shops)
• The battery and inverter can be scheduled — most current Sungrow, Growatt, and similar systems can

If you are out all day and only use power in the evening, a battery charged from solar (and topped up at night) is often a better fit than solar alone, which would otherwise be exported cheaply while you are at work.

What to watch

• Tariff maths. A cheap night rate only helps if the daytime rate you avoid is meaningfully higher. Check the actual pence, not just the marketing name.
• Battery cycle life. Quality systems are designed for daily cycling. Charging every night is normal — that is what they are for.
• Don't overfill from the grid when solar will do it. A proper setup charges from solar first and only uses the overnight window for the shortfall.
• Export vs import. You still want surplus solar used on site or stored, not dumped to the grid for pennies if you could have kept it.

Homes and businesses

Homes: Charge overnight, run the house and any heat pump or EV from the battery in the morning, and let solar refill through the day. Many Spalding households on an off-peak tariff see a clear drop in the daytime portion of the bill.

Businesses: Cold stores, packhouses, and workshops that start early can begin the shift on cheap stored power, then let solar and the battery cover the working day. That is the same idea as our guide to commercial battery payback — night charging is a big part of it.

Bottom line

Charging a solar battery at night is not a backup plan for bad weather. It is a deliberate way to buy electricity when it is cheap and use it when it is expensive, while still taking every free kWh your panels produce.

Get the tariff, the battery size, and the charge schedule right, and the system quietly does the work while you sleep.

Want this set up properly?

PPM Electrical designs and installs MCS accredited solar and battery systems from our base in Spalding, including overnight charge schedules on compatible inverters.

Call 07714 736921, email info@ppmelectricalspalding.co.uk, or send a message. Read more about our battery storage installations.

Savings depend on your tariff, battery size, and how you use power. Overnight and daytime rates above are typical 2026 UK ranges for guidance — check your own supplier before you rely on the numbers.